Oki Fax Machine ML520 User Manual
Page: 1  
Service Guide ML520/521  
Chapter 0 About This Manual  
ML520 // ML521  
Dot Matrix Printers  
Adobe Acrobat printable reference  
copy of the OKIDATA Service Training Manual.  
09/17/97  
Note: This Adobe Acrobat version of the Okidata Service Training Manual was built with the  
pictures rendered at 300 dpi, which is ideal for printing, but does not view on most  
displays well.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Table of Contents  
Page  
........Head Drive Time  
........Print Speed  
........%Head Overheat Alarm Processing  
....2.1.08 Power Supply Circuit  
2.2 Mechanical Operation - Printhead Mechanism  
........Printhead Gap Information  
........Interconnect Diagram: Control Board to Printhead  
........Line Feed Motor Resistance  
........Space Motor Resistance  
........Printhead Operation  
........Printhead Temperature  
....2.2.02 Spacing Mechanism  
........Spacing Operation  
....2.2.03 Head Gap Mechanism  
........Ribbon Drive Operation  
....2.2.05 Line Feed Mechanism  
........Cut Sheet/Continuous Sheet Switching Mechanism  
........Cut Sheet Paper Feed Operation  
........Continuous Paper Feed (Rear Tractor Mechanism)  
........Continuous Paper Feed (Pull Tractor Mechanism)  
........Continuous Paper Feed (Bottom Tractor Feed  
Mechanism)  
39  
40  
41  
42  
43  
44  
45  
46  
47  
48  
49  
50  
51  
52  
53  
54  
55  
56  
57  
58  
59  
........Continuous Paper Feed (Push/Pull Tractor Mechanism)  
....2.2.06 Paper Detection Mechanism  
....2.2.07 Support Protector Mechanism  
....2.2.08 Automatic Paper Load  
........Continuous Feed Paper  
60  
61  
62  
63  
64  
65  
....2.2.09 Paper Park  
3 Maintenance & Disassembly  
....3.1.01 General Information  
66  
67  
68  
69  
70  
71  
72  
73  
74  
75  
....3.1.02 Maintenance Tools  
....3.1.03 Maintenance Precautions  
3.2 Disassembly/Assembly Procedures  
....3.2.01 Preliminary Items  
....3.2.02 Printhead Assembly  
....3.2.03 Ribbon Protector  
....3.2.04 Gear Case Assembly  
....3.2.05 Pull-up Roller Assembly  
....3.2.06 Upper Cover, Access Cover, and Sheet Guide  
Assemblies  
....3.2.07 Control Board (FJIM)  
76  
77  
78  
79  
....3.2.08 Power Supply Assembly  
....3.2.09 Operator Panel PCB (LEOP)  
....3.2.10 PC Connector  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Table of Contents  
Page  
....3.2.11 Space Motor and Roller Guide Assemblies  
....3.2.12 Carriage Cable  
80  
81  
....3.2.13 Space Rack  
82  
....3.2.14 Roller/Holder Backup Assembly  
....3.2.15 Guide Rail and Adjust Cam  
....3.2.16 Left Ground Plate  
....3.2.17 Right Ground Plate  
....3.2.18 Rear and Cut Sheet Paper Feed Sensor Levers  
....3.2.19 Platen Assembly  
83  
84  
85  
86  
87  
88  
....3.2.20 Paper Chute Assembly  
....3.2.21 Line Feed Motor Assembly  
....3.2.22 Reset Spring  
89  
90  
91  
....3.2.23 Idle Gear and Change Lever  
....3.2.24 Pressure Spring  
92  
93  
....3.2.25 Carriage Shaft  
94  
....3.2.26 Leaf Spring  
95  
....3.2.27 Bottom Paper Sensor Levers  
....3.2.28 Front Pressure Roller Assembly  
....3.2.29 Tractor Assembly  
....3.2.30 Main Frame  
96  
97  
98  
99  
3.3 Printer Adjustments  
100  
101  
102  
103  
104  
105  
106  
107  
108  
109  
110  
111  
112  
....3.3.02 Printhead Gap Adjustment  
....3.3.03 Key Combinations  
....3.3.04 Menu Operation  
........Menu Settings  
....3.3.05 Top of Form  
....3.3.06 Paper Park  
....3.3.07 Tear Feature  
....3.3.08 Forms Tear Off  
....3.3.09 Resets  
3.4 Cleaning  
3.5 Lubrication  
3.6 Shipping Instructions  
4 Failure & Repair Analysis  
....4.1.01 Introduction  
113  
114  
115  
116  
117  
118  
119  
120  
121  
122  
....4.1.02 Printer Serial Number Identification  
....4.1.03 Firmware Revision Identification  
4.2 Reporting Problems - General Information  
....4.2.02 Problem Lists  
....4.2.03 Reporting Methods  
4.3 Troubleshooting Updates  
4.4 Troubleshooting Tips  
....4.4.02 Problem Categories  
....4.4.03 START HERE Flowchart  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Table of Contents  
Page  
....4.4.04 Tips for Preventing Image Problems  
....4.4.05 Common Problems  
4.5 Abnormal Output - Output Samples  
....Left Margin Drifting Problem  
123  
124  
125  
126  
127  
128  
129  
130  
131  
132  
133  
134  
135  
136  
137  
138  
139  
140  
141  
142  
143  
144  
145  
146  
147  
148  
149  
150  
151  
152  
153  
154  
155  
4.6 Fault Alarms  
....4.6.02 ALARM/LED Display Troubleshooting Table Index  
....4.6.03 ALARM/LED Display Troubleshooting Tables  
4.7 Repair Analysis Procedures (Raps)  
....4.7.02 RAP Index  
........RAP 01 No Power Supplied to Printer  
........RAP 02 No Spacing Operation  
........RAP 03 Printhead Homing Error  
........RAP 04 Paper Jam During Paper Loading  
........RAP 05 Printhead Pins Not Firing  
........RAP 06 Poor Print Quality  
........RAP 07 Ribbon Feed Problem  
........RAP 08 Line Feed Problem  
........RAP 09 Operation Panel Malfunction  
........RAP 10 Parallel Interface Problem  
........RAP 11 Serial Interface Problem  
4.8 Printer Tests  
....4.8.02 Rolling ASCII Test  
....4.8.03 Font Test  
....4.8.04 Serial Interface Loopback Test  
........Serial Cable Information  
........Serial Interface Signal Requirements  
........Commonly Used Serial Cable Configurations  
....4.8.05 Hexadecimal Dump Mode  
4.9 Resistance Checks  
........Layout Diagram  
....4.9.02 Printhead  
....4.9.03 Line Feed Motor Resistance  
....4.9.04 Space Motor Resistance  
A Reference Charts  
A.1 Overview - A.1.01 General Information  
A.2 Index To Charts  
........Board Layout  
....A.2.01 Main Controller Board (FJIM)  
....A.2.02 Operator Panel Board (LEOP)  
....A.2.03 Power Supply Assembly  
....A.2.04 Space Motor Board  
156  
157  
158  
159  
160  
161  
162  
163  
....A.2.05 RS232-C Serial Interface Board - Option (LXHI)  
B Illustrated Parts Listing  
B.1 Overview - B.1.01 General Information  
164  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Table of Contents  
Page  
........Format  
165  
166  
167  
168  
169  
170  
171  
172  
173  
174  
175  
176  
177  
178  
179  
180  
181  
182  
183  
........Current Part Numbers  
....B.1.02 Definition of Terms  
....B.1.03 Parts Ordering Information  
B.2 Charts  
........Overview  
....B.2.01 Printer  
....B.2.02 Upper Cover Assembly  
....B.2.03 Printer General Assembly  
....B.2.04 Printer Unit  
....B.2.05 Printer Unit  
....B.2.06 Printer Unit  
....B.2.07 Carriage Assembly  
....B.2.08 Options  
....B.2.09 Option Parts  
....B.2.10 Consumables  
....B.2.11 Packing Materials  
....B.2.12 Documentation  
....B.2.13 Service Training Kit Revision List  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 2  
Service Guide ML520/521  
Chapter 0 About This Manual  
This document may not be reproduced without the written permission of the Okidata Technical  
Training Group. Every effort has been made to ensure the accuracy of the information contained  
in this training course. Okidata is not responsible for errors beyond its control.  
© 1994 by Okidata All rights reserved.  
First Edition  
February, 1993  
September, 1993  
December, 1994  
P/N 59257801  
P/N 59257802  
Second Edition  
Third Edition  
P/N 59257803  
Written and produced by the Okidata Technical Training Group  
Please address any comments on this publication to:  
Technical Training Group  
Okidata  
532 Fellowship Road  
Mount Laurel, NJ 08054-3499  
Fax Number: (609) 235-2600, ext. 7034  
Okilink Login Name: Technical Training  
OKIDATA is a registered trademark of Oki Electric Industry Company, Ltd.; marques deposee de  
Oki Electric Industry Company, Ltd.; marca registrada, Oki Electric Industry Company, Ltd.  
MICROLINE is a registered trademark of Oki Electric Industry Company, Ltd.; marque depose de  
Oki Electric Industry Company, Ltd.  
OkiSmart Paper Handling is a trademark of Oki Electric Industry Company, Inc.  
PLUG n PRINT is a registered trademark of Oki America, Inc.; marque deposee de Oki America,  
Inc.  
Bitstream is a registered trademark of Bitstream Incorporated.  
Epson is a registered trademark of Seiko Epson Corporation.  
IBM is a registered trademark of International Business Machine Corporation.  
MS-DOS is a registered trademark of Microsoft Corporation.  
PC is a registered trademark of International Business Machine Corporation.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Proprinter is a registered trademark of International Business Machine Corporation.  
Windows is a trademark of Microsoft Corporation  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 3  
Service Guide ML520/521  
Chapter 1 Product Specifications  
1.1.01 General Information  
The Microline 520 and Microline 521 are letter quality, nine-pin, dot-matrix printers which utilize  
OKISMART paper handling. Patented Okidata technology does away with the manual head gap  
adjustment. The printer actually reads and learns the print medium being used, then automatically adjusts  
the head gap to the optimum distance. This autogapping process leads to longer printhead life.  
Options include the Bottom Feed Push Tractor, Cut-Sheet Feeder, Pull Tractor and Serial Interface Board.  
The Microline 520 is an 80 column printer.  
The Microline 521 is a 132 column printer.  
Okidata's one year limited warranty covers the parts, labor and printhead on both printers.  
The following items are available for the printer.  
OKISMART Typer - software which provides the flexibility for the Microline 590/521 to function like a  
typewriter on checks, labels and envelopes.  
OKISMART Panel - a utility program that lets you control selected printer functions from your personal  
computer.  
Scalable Fonts - 14 scalable fonts, available on diskette.  
NOTE:  
The OkiSmart software includes three programs.  
1. OkiSmart Control  
2. OkiSmart Panel Emulator  
3. OkiSmart Setup  
Refer to the Printer Handbook for more information.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 4  
Service Guide ML520/521  
Chapter 1 Product Specifications  
1.2 PHYSICAL SPECIFICATIONS  
1.2.01 Dimensions  
NOTE:  
Dimensions INCLUDE the platen knob, acoustic cover, and paper separator.  
Microline 520  
Width: 16.9 inches (43 centimeters)  
Depth: 14.9 inches (37.8 centimeters)  
Height: 6.5 inches (16.5 centimeters)  
Microline 521  
Width: 23 inches (58.4 centimeters)  
Depth: 14.9 inches (37.8 centimeters)  
Height: 6.5 inches (16.5 centimeters)  
1.2.02 Printer Weight  
Microline 520  
17.6 pounds (8.0 kilograms)  
Microline 521  
23.1 pounds (10.5 kilograms)  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 5  
Service Guide ML520/521  
Chapter 1 Product Specifications  
1.3 POWER REQUIREMENTS  
1.3.01 Input Power  
120 VAC: +5.5 / -15%  
230/240 VAC: +10 / -14%  
1.3.02 Power Consumption  
Operating: 110 VA  
Idle: 40 VA  
Local Test: 70 VA  
1.3.03 Power Frequency  
120 VAC: 60 Hz +/- 2%  
230/240 VAC: 50/60 Hz +/- 2%  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 6  
Service Guide ML520/521  
Chapter 1 Product Specifications  
1.4 ENVIRONMENTAL CONDITIONS  
1.4.01 Acoustic Rating  
Near Letter Quality Mode  
Microline 520 54.9 dBA  
Microline 521 54.4 dBA  
Utility Mode  
Microline 520 57.2 dBA  
Microline 521 56.9 dBA  
Quiet Mode  
Microline 520 52.5 dBA  
Microline 521 52.3 dBA  
1.4.01 Altitude  
10,000 feet (3,050 meters)  
1.4.03 Ambient Temperature and Relative Humidity (RH)  
While operating: 41 to 104 degrees Fahrenheit (5 to 40 degrees Celsius)  
Operating humidity: 20% to 80% RH  
While in storage: 14 to 122 degrees Fahrenheit ( - 10 to 50 degrees Celsius)  
Storage humidity: 5% to 95% RH  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 7  
Service Guide ML520/521  
Chapter 1 Product Specifications  
1.5 AGENCY APPROVALS  
1.5.01 Listings  
UL No: UL Standard No. 1950 D3  
CSA No: CSA Standard 22.2-950 D3  
FCC: FCC Certified per Part 15, Subject J, Class B  
IEC: IEC 950  
VDE: VDE 0805 VDE 0875 Class B  
BS: BS 7002  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 8  
Service Guide ML520/521  
Chapter 1 Product Specifications  
1.6 OPERATIONAL SPECIFICATIONS  
1.6.01 Character Matrix Sizes  
Table of Print Speed and Character Matrix  
Mode  
Speed  
Matrix (H x V)  
Near Letter Quality  
80 (12cpi)  
17 x 13  
Utility  
320 (12cpi)  
9 x 7  
High Speed Draft  
427 (12cpi)  
7 x 7  
Print Speed at Different CPI for the ML 520/521  
Mode  
HSD  
CPI  
10  
CPS  
427  
427  
427  
427  
427  
320  
320  
320  
320  
320  
80  
Horiz. DPI  
Vert. DPI  
72  
IPS  
90  
42.7  
35.6  
28.5  
25.0  
21.4  
32  
12  
108  
135  
154  
180  
120  
144  
180  
206  
240  
240  
288  
360  
412  
480  
72  
15  
72  
17.1  
20  
72  
72  
10  
72  
Utility  
12  
72  
26.7  
21.3  
18.6  
16.0  
16.0  
13.3  
13.3  
9.32  
8.0  
15  
72  
17.1  
20  
72  
72  
10  
144  
144  
144  
144  
144  
LQ  
12  
80  
15  
80  
17.1  
20  
80  
80  
1.6.02 Characters Per Line  
Microline 520  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Characters Per Line  
Characters Per Inch  
80  
96  
10  
12  
120  
137  
160  
15  
17.1  
20  
Microline 521  
Characters Per Line  
Characters Per Inch  
136  
163  
204  
233  
272  
10  
12  
15  
17.1  
20  
1.6.03 Character Pitches  
5, 6, 8.5, 10, 12, 15, 17.1, 20  
1.6.04 Character Sets  
Standard ASCII  
EPSON Character Set I & II  
IBM Character Set I, II & All Characters  
Foreign Character Substitution  
International Character Sets  
Code Page 850, 860, 863, 865 and 437  
Line Graphics  
Bar Code  
Code 39  
UPC A  
UPC E  
EAN 8  
EAN 13  
Interleaved 2 of 5  
Code 128 (A, B, C)  
Postnet  
Download from Www.Somanuals.com. All Manuals Search And Download.  
1.6.05 Emulations  
NOTE: The emulations are co-resident  
Epson FX  
IBM Proprinter  
Microline Standard  
1.6.06 Fonts  
Near Letter Quality  
Courier  
Utility  
Gothic  
High Speed Draft  
Gothic  
Bar Code  
Code 39  
UPC A  
UPC E  
EAN 8  
EAN 13  
Interleaved 2 of 5  
Code 128 (A, B, C)  
Postnet  
1.6.07 Front Panel Switches  
SELECT / Menu Micro Feed Up / Down  
Shift Paper Park  
Line Feed Pitch Selection  
FORM FEED / Load Print Quality Selection  
Top of Form Tear  
Quiet Reset  
1.6.08 Graphics Resolution  
Graphics Resolution: 288 (horizontal) x 144 (vertical) dots per inch (DPI) maximum  
1.6.09 Interface  
Standard  
Centronics Parallel  
Optional  
Download from Www.Somanuals.com. All Manuals Search And Download.  
RS232C Serial  
1.6.10 Line Feed Increments  
Fixed  
6 lines per inch (lpi) [0.167 inch (4.23 millimeters)]  
8 lines per inch (lpi) [0.125 inch (3.175 millimeters)]  
Variable  
n/60 inch  
n/72 inch  
n/144 inch  
n/216 inch  
1.6.11 Line Feed Time  
65 milliseconds 6 lines per inch (lpi)  
6 milliseconds 8 lines per inch (lpi)  
1 second 5.0 inches (Continuous paper feed rate)  
1.6.12 Menu Mode  
Switch  
Action  
Paper park  
Prints the entire menu.  
Selects Group Function  
Selects Item  
Line Feed / Reverse  
FORM FEED / Load  
Tear  
Selects Item Value  
SEL / Menu  
Exits Menu Mode, Enters Select  
1.6.13 Paper Feed Methods  
Standard  
Friction Feed (Top)  
Rear Push Tractor (Rear)  
Optional  
Pull Tractor (Bottom)  
Bottom Push Tractor Feed (Bottom)  
Single-Bin Cut Sheet Feeder (Top)  
CSF 5000 - Narrow  
CSF 5001 - Wide  
1.6.14 Paper Feed Paths  
Top Feed (Standard)  
Rear Feed (Standard)  
Bottom Feed (by using an Optional feed mechanism)  
Special Features  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Paper Park  
Automatic Paper Loading  
Forms Tear Off  
1.6.15 Paper Loading  
Auto Loading (Top Feed)  
Press FORM FEED / Load switch to feed paper to default position  
1.6.16 Paper Out Detection  
Distance from end of paper  
Rear Feed: 0.5 inches (12.7 mm)  
Bottom Feed: 0.5 inches (12.7 mm)  
Top Feed: 0.5 inches (12.7 mm)  
1.6.17 Paper Tear Capabilities  
Forms Tear-0ff (sharp edge on access cover)  
Metal Tear Bar (with optional bottom feed tractor unit)  
1.6.18 Print Method  
Printhead Type  
General Information  
Impact: Dot Matrix  
9 pin printhead  
.0134 inch (0.34 millimeter) diameter pins  
Overheat Protection  
When printhead temperature exceeds 110 degrees Celsius, the printer stops bi-directional printing.  
Uni-directional printing begins.  
If the temperature exceeds 118 degrees Celsius, printing stops.  
Printing will resume when the printhead temperature drops below 118 degrees Celsius.  
NOTE:  
Refer to Section Two for more information on printhead operation.  
Printhead Gap Information  
Three items factor into printhead gap information:  
Download from Www.Somanuals.com. All Manuals Search And Download.  
1. Printhead Gap Adjustment  
This is a SERVICE ADJUSTMENT made by a technician.  
It is covered in Section 3.3 of this Service Handbook.  
The Adjustment measures 0.014 +/- 0.001 inches 90.35, +/-0.03 mm).  
2. Printhead Gap Adjustment  
This is a MENU ITEM in the SET-UP Group.  
It fine tunes the automatic setting of the printhead gap.  
The settings are 0, 1 and -1.  
Use 1 to darken print (if output is consistently light).  
Use -1 to lighten print (if output is consistently dark).  
3. Gap Control  
This is a MENU ITEM in each (Paper Feed) Group.  
The Groups are REAR FEED, BOTTOM FEED, and TOP FEED.  
Gap Controls determines how the printhead gap is set.  
The settings are listed below.  
Auto Gap, Semi Auto Gap, 1, 2, 3, 4, 5, 6, 7, 8, 9  
An explanation of each setting follows.  
Auto Gap  
This is the factory default.  
Automatically determines paper thickness of the first page.  
During single-sheet feed, each page's thickness is checked while a job is  
printing.  
Semi Auto Gap  
Similar to Auto Gap.  
Automatically determines paper thickness of the first page.  
During single-sheet feed, each page's thickness IS NOT checked "while" a  
job is printing.  
1, 2, 3, 4, 5, 6, 7, 8, 9  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Used when the same paper is used ALL of the time.  
Bypasses the automatic head gap adjustment.  
1 is the narrowest head setting.  
9 is the widest head setting.  
1.6.19 Print Modes  
Near Letter Quality  
Utility  
High Speed Draft  
1.6.20 Print Speed  
Table of Print Speed and Character Matrix  
Mode  
Speed  
Matrix (H x V)  
Near Letter Quality  
80 (12 cpi)  
Utility  
320 (12 cpi)  
9 x 7  
High Speed Draft  
427 (12 cpi)  
7 x 7  
17 x 13  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 9  
Service Guide ML520/521  
Chapter 1 Product Specifications  
1.7 PAPER SPECIFICATIONS  
CAUTION:  
Use Bottom Feed and/or optional Pull Tractor for card stock and labels.  
1.7.01 Types  
Card Stock  
Weight: 120 lbs. (450 g/m 2 ) Maximum  
Width: Microline 520 5 to 8 inches (12.7 to 20.3 centimeters)  
Microline 521 5 to 14 inches (12.7 to 35.6 centimeters)  
Length: 3 to 17 inches (7.62 to 43.18 centimeters)  
Thickness: .017 inches (0.44 millimeters)  
Paper Feed Path: Bottom  
Printhead Gap Information: Refer to the Printhead Gap Information, Section 1.6  
Continuous Form  
Weight:  
Single Part 12 - 24 lb. (45 to 90 g/m 2 )  
Multi-Part, Carbonless 9 - 11 lb. (35 to 40 g/m 2 )  
Multi-Part, Interleaf Paper 10 - 12 lb. (38 to 45 g/m 2 ) Carbon 9 lb. (35 g/m 2 )  
Width: Microline 520 3.5 to 10.5 inches (8.8 to 26.6 centimeters)  
Microline 521 3.5 to 16.5 inches (8.8 to 41.9 centimeters)  
Length: 3 to 17 inches (7.62 to 43.18 centimeters)  
Thickness: 0.014 inches (0.36 millimeters) Rear Feed 0.017 inches (0.44 millimeters) Bottom  
Feed  
Paper Feed Path: Rear or Bottom  
Printhead Gap Information: Refer to the Printhead Gap Information, Section 1.6  
Cut Sheet  
Weight: 12 to 24 lbs. (45 to 90 g/m 2 )  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Width: 7.2 to 14.3 inches (18.3 to 36.3 centimeters)  
Width: Microline 520 7.2 to 8.5 inches (18.2 to 21.5 centimeters)  
Microline 521 7.2 to 14.3 inches (18.2 to 36.3 centimeters)  
Length: 3 to 17 inches (7.62 to 43.18 centimeters)  
Thickness: 0.014 inches (0.325 millimeters) Maximum  
Paper Feed Path: Top  
Printhead Gap Information: Refer to the Printhead Gap Information, Section 1.6.  
Envelopes  
Weight: 24 lbs. (90 g/m 2 ) Maximum  
Size:  
Single Feed  
Minimum: 6.5 x 3.6 inches (16.5 x 9.1 centimeters)  
Maximum: 9.5 x 4.1 inches (24.1 x 10.4 centimeters)  
Continuous  
Non-overlap type  
Thickness: .014 inches (.325 millimeters) Maximum  
Paper Feed Path: Bottom  
Printhead Gap Information: Refer to the Printhead Gap Information, Section 1.6.  
Labels  
Weight: N/A  
Width: Microline 520 3.5 to 10.5 inches (8.8 to 26.6 centimeters)  
Microline 521 3.5 to 16.5 inches (8.8 to 41.9 centimeters)  
Length: 3 to 17 inches (7.62 to 43.18 centimeters)  
Thickness: .011 inches (0.28 mm) Maximum (including backing)  
Paper Feed Path: Bottom  
Printhead Gap Information: Refer to the Printhead Gap Information, Section 1.6.  
CAUTION:  
Use Bottom Feed and/or optional Pull Tractor for card stock and labels.  
Transparency  
Download from Www.Somanuals.com. All Manuals Search And Download.  
NOTE:  
Roller marks may mar the transparency under high temperature / high humidity conditions.  
Weight: 12 to 24 lbs. (45 to 90 g/m 2 )  
Width: Microline 520 7.2 to 8.5 inches (18.2 to 21.5 centimeters)  
Microline 521 7.2 to 14.3 inches (18.2 to 36.3 centimeters)  
Length: 3 to 17 inches (7.62 to 43.18 centimeters)  
Thickness: 0.14 inches (0.36 millimeters)  
Paper Feed Path: Top  
Printhead Gap Information: Refer to the Printhead Gap Information, Section 1.6.  
1.7.02 Length  
NOTE:  
The recommended length is specific to paper type.  
Rear Feed  
Minimum 3 inches (7.62 centimeters)  
Maximum 17 inches (43.18 centimeters)  
Bottom Feed  
Minimum 3 inches (7.62 centimeters)  
Maximum 17 inches (43.18 centimeters)  
Top Feed  
Minimum 3 inches (7.62 centimeters)  
Maximum 17 inches (43.18 centimeters)  
1.7.03 Number of Copies  
Original + 4 Interleaf  
Original + 4 Carbonless  
Original Cut Sheet  
1.7.04 Thickness  
0.014 inches / 0.36 mm Maximum Thickness, Rear Feed  
0.017 inches / 0.44 mm Maximum Thickness, Bottom Feed  
1.7.05 Weight  
Download from Www.Somanuals.com. All Manuals Search And Download.  
NOTE:  
The recommended weight is specific to paper type.  
Minimum: 9 lb. (35 g/m 2 )  
Maximum: 120 lb. (90 g/m 2 )  
1.7.06 Width  
NOTE:  
The recommended width is specific to paper type.  
Paper  
Microline 520  
Minimum: 3.5 inches ( 8.8 centimeters)  
Maximum: 10.5 inches (26.6 centimeters)  
Microline 521  
Minimum: 3.5 inches ( 8.8 centimeters)  
Maximum: 16.5 inches (41.9 centimeters)  
Printing Area  
Microline 520 8 inches Maximum  
Microline 521 13.6 inches Maximum  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 10  
Service Guide ML520/521  
Chapter 1 Product Specifications  
1.8 MEMORY SPECIFICATIONS  
1.8.01 EEPROM  
1 Kbit serial EEPROM (used to store Menu data)  
1.8.02 EPROM  
1 MBit EPROM (Printer Control Program - Fonts)  
1.8.03 RAM  
128 Kbyte Total Resident RAM  
Used as  
Receive Buffer  
Receive Buffer Size is selected through the Menu.  
Settings are: 64 K, 32 K, 1 line  
Print Buffer  
DLL Buffer  
Scratch Pad  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 11  
Service Guide ML520/521  
Chapter 1 Product Specifications  
1.9 CONSUMABLES  
1.9.01 Ribbon  
CAUTION:  
Using a non-Okidata ribbon may damage the printhead and void any warranties.  
Material  
Nylon fabric, cartridge type, re-inking  
Type  
Black Ribbon  
Life (On average, at 10 characters per inch, Utility Mode)  
4 million characters  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 12  
Service Guide ML520/521  
Chapter 1 Product Specifications  
1.10 OPTIONS - Cut Sheet Feeders  
1.10.01 Cut Sheet Feeders  
Single Bin  
The CSF-5000 is a narrow feeder for the Microline 520.  
Single Bin with envelope capability  
Paper Width: 7.2" to 8.5" (18.3 cm to 36.3 cm)  
Paper Length: 10.1" to 14" (25.6 cm to 35.6 cm)  
Capacity: 170 sheets (16 lb.), 100 sheets (20 lb.)  
The CSF-5001 is a wide feeder for the Microline 521.  
Single Bin with envelope capability  
Paper Width: 7.2" to 14.3" (18.3 cm to 36.3 cm)  
Paper Length: 10.1" to 14" (25.6 cm to 35.6 cm)  
Capacity: 170 sheets (16 lb.), 100 sheets (20 lb.)  
Dual Bin  
P/N 70022601 is a narrow feeder for the Microline 520.  
Dual Bin with envelope capability  
Paper Width: 7.2" to 8.5" (18.3 cm to 36.3 cm)  
Paper Length: 10.1" to 14" (25.6 cm to 35.6 cm)  
Capacity: 170 sheets (16 lb.), 100 sheets (20 lb.)  
P/N 70022801 is a wide feeder for the Microline 521.  
Dual Bin with envelope capability  
Paper Width: 7.2" to 14.3" (18.3 cm to 36.3 cm)  
Paper Length: 10.1" to 14" (25.6 cm to 35.6 cm)  
Capacity: 170 sheets (16 lb.), 100 sheets (20 lb.)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 13  
Service Guide ML520/521  
Chapter 1 Product Specifications  
1.10.02 Pull Tractor Kit  
NOTE:  
The Pull Tractor Kit (P/N 70023001) is a narrow feeder for the Microline 520.  
The Pull Tractor Kit (P/N 70023201) is a wide feeder for the Microline 521.  
Bottom Feed  
Rear Feed (For Push/Pull Operation)  
Paper Types: Continuous Feed and Labels  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 14  
Service Guide ML520/521  
Chapter 1 Product Specifications  
1.10.04 Bottom Push Tractor Kit  
NOTE:  
The Bottom Push Tractor Kit (P/N 70022901) is a narrow feeder for the Microline 520.  
The Bottom Push Tractor Kit (P/N 70023101) is a wide feeder for the Microline 521.  
Bottom Feed  
Paper Type: Continuous Feed  
Includes: Stand and Metal Tear Bar  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 15  
Service Guide ML520/521  
Chapter 1 Product Specifications  
1.10.05 Serial Interface  
Super-Speed 19.2K RS-232C  
Ready/Busy/X-On/X-Off Protocols  
Can be configured through the Menu or OKISmart Utility Program  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 16  
Service Guide ML520/521  
Chapter 1 Product Specifications  
1.10.06 Roll Paper Stand  
Adapts printer for use with roll-type paper (Model 520 only)  
Includes: Stand, Support, Cord and DIN plug for connection to printer  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 17  
Service Guide ML520/521  
Chapter 1 Product Specifications  
1.10.08 OKISmart Typer Utility  
Obtained via BRC (Business Reply Card) packaged with printer  
Includes: Typewriter Mode, Form Creation Utility and Barcode Utility  
1.10.09 OKISmart Panel Utility  
Obtained via BRC (Business Reply Card) packaged with printer  
Includes: Front Panel Control Utility and Drivers for Windows 3.0 & 3.1  
NOTE:  
The OKISmart software includes three programs.  
1. OKISmart Control  
2. OKISmart Panel Emulator  
3. OKISmart Setup  
Refer to the Printer Handbook for more information.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 18  
Service Guide ML520/521  
Chapter 1 Product Specifications  
1.11 RELIABILITY  
1.11.01 Mean Time Before Failure (MTBF)  
Approximately 6,000 hours: 25% duty cycle / 35% page density  
1.11.02 Mean Time To Repair (MTTR)  
Approximately 15 minutes to major sub-assembly level  
1.11.03 Printer Life  
Approximately 16,000 hours of power-on time: 25% duty cycle / 35% page density  
1.11.04 Printhead Life  
Average 200 million characters in 10 cpi utility mode @ normal 25% duty, 35% page density  
1.11.05 Ribbon Life  
Approximately 4 million characters  
1.11.06 Warranty (Limited)  
One year, parts and labor  
1.11.07 Service  
Authorized OKIDATA Service Centers  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 19  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
2.1 ELECTRICAL OPERATION  
The printer is comprised of the electrical components listed below.  
Main Control Board  
Power Supply Assembly  
Transformer  
Filter Board  
Operator Panel  
Space Motor / Line Feed Motor  
Printhead  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 20  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
2.1.01 Main Control Board  
The main control board is made up of the microprocessor, peripheral circuits, drive circuits, sensors and  
interface connectors.  
The power to the main control board is supplied by the transformer assembly through a wire harness.  
The power to other electrical parts (line feed motor, space motor and printhead) is provided by the power  
supply circuitry through connectors on the main control board.  
Microprocessor (MPU) (Location 04C: 67X640)  
16 bit MPU, using CMOS technology.  
The MPU contains a 20 bit address bus, a 16 bit data bus.  
The MPU can access 1 Mbyte of program memory and 1 Mbyte of data memory space.  
The microprocessor controls the entire printer by executing the control program through the  
LSIs and the driver circuits.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 21  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Block Diagram  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 22  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Program ROM  
Location 05CA: 27C1024  
This 64k x 16 bit (1Mbit) EPROM contains the control program for the printer. The MPU executes the  
instructions contained in this program.  
The Program ROM is assigned to the program memory area of the MPU and instructions are fetched by  
the PSEN signal of the MPU.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 23  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
RAM  
Location 05CB: 511664Z  
The RAM is CMOS dynamic RAM with 65,536 words x 16-bit configuration. It is used as a receive buffer,  
print buffer and work buffer.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 24  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
LSI  
Location 04B: MSM79VO35  
Detects the output of the two-phase sensor on the DC space motor to control the motor drive phase.  
Transmits and receives serial data to and from the printhead based on the dot timing (which is derived  
from the space motor speed).  
Controls the external interface. The LSI is connected to the MPU.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 25  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Electrically Erasable Programmable Read Only Memory (EEPROM)  
(Location 03C: 93CS46)  
The EEPROM is a CMOS serial I/O type memory (EEPROM). It is capable of electrically erasing and  
writing 1,024 bits.  
The EEPROM contains the menu data and the head drive time correction data.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 26  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
2.1.02 Initialization  
This printer is initialized when the printer is powered on or when the I-PRIME-N signal is input from the  
host via the parallel interface.  
The steps in Printer Initialization are listed below.  
The RST-N signal is output from the reset circuit to reset the MPU and LSIs.  
The program is executed and the LSIs are reset by the MPU via IORST-N.  
NOTE:  
A reset operation initiated by I-PRIME does not reset the MPU.  
The program sets the LSI (02D) mode, checks the memory (ROM/RAM), then executes carriage homing  
and determines the phase of the line feed motor.  
Finally, the program establishes the interface signals (P-I/F: ACK-P signal sending, and S-I/F: BUSY-N  
signal off) and lights the SELECT lamp to indicate that the printer is in the ON-LINE state.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 27  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
2.1.03 Parallel Interface Control  
The parallel data input from the host to the interface LSI is latched to the internal register at the falling  
edge of the STROBE-N signal.  
The LSI sets the BUSY-N signal to inform the host that the data is being processed. The LSI also outputs  
the RXD-N signal to inform the MPU of data reception. The data is read upon receiving the RD-N signal  
from the MPU.  
When the data processing is complete, the BUSY-N signal is disabled and the ACK-N signal is sent to  
request the next data. When the buffer is full and reception is not desired, the BUSY signal is sent to  
request data transmission be stopped.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 28  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
2.1.04 Print Control  
The print data is transmitted as serial data from the LSI to the control circuit and the driver contained in  
the printhead.  
After the data is printed, the sensor analog circuit controlling each pin returns the pin stroke data to the  
MPU. The MPU will make an automatic head gap adjustment. This feedback system sets the optimum  
drive time for each pin in order to maintain high print quality.  
In the case of envelopes, where the medium thickness varies as the printhead moves along the platen,  
the strike force of the pins changes to compensate for the differences in thickness.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 29  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
LSI/Printhead Interface  
The connection between the LSI and the printhead is made with the bi-directional serial data bus. The LSI  
transmits the print data as serial data to the logic circuit of the printhead. The printhead returns serial data  
from the printhead sensor analog circuit to the LSI. This information is used to determine the optimum  
drive time for the next print request.  
The logic circuit of the printhead signals the LSI if a parity error is detected in the print data.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 30  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Gap Adjust Control  
The Gap Adjust LSI receives stroke length information for all of the printhead pins from the sensor analog  
circuit. The Gap Adjust LSI then sets the optimum printhead gap for the printing medium.  
NOTE:  
Refer to Section 2.2.03 for a description of the mechanical process.  
All values in the below chart are in millimeters  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 31  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Print Compensation Control  
The printhead compensates for the shape of the platen as shown below.  
NOTE:  
Also refer to Section 2.1.07 - Head Drive Time  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 32  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
2.1.05 Space and Line Feed (SP/LF) Motor Control  
The LSI (Location 04B: MSM79V035) generates the space motor and the line feed motor control signals  
according to commands received from the MPU. These signals are sent to the SP/LF motor driver.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 33  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Line Feed Motor Control  
The SP/LF motor driver (Location 5A: MHM2025) drives the line feed motor in two-phase bipolar, based  
on the phase changeover data output from the LSI.  
The serial data from the LSI (04B: MSM79V035) is processed by a register contained in the SP/LF motor  
driver to measure the overdrive time and to change the phase.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 34  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Space Motor Control  
The SP/LF motor driver (Location 5A: MHM2025) drives the three-phase brushless motor. Motor  
movement is based on the phase signal (SPU, SPV and SPW) and the speed instruction data from the  
LSI. The MPU can identify the current speed of the space motor by measuring the pulse width of the  
output (Phase A, Phase B) of the encoder disk sensor.  
After comparing the target speed for each print mode with the actual speed, the motor is accelerated or  
decelerated to maintain the desired speed for each print mode.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 35  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Encoder Disk  
As the space motor operates, the encoder disk spins. When the encoder disk interrupts the photo  
sensors, the signals Phase A and Phase B are generated. The LSI (Location 04B: MSM79V035) divides  
these edge pulse signals (the frequency division is based on the selected print pitch) to generate the  
signal IPT. The IPT signal provides dot-on timing and carriage position detection timing.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 36  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
2.1.06 Operation Panel  
The Serial I/O Port (Ports 20 - 23) of the MPU reads the operation panel switch data from the operation  
panel control LSI (Location IC1: BUS148S).  
A two byte (15 bits +1 parity bit (even parity)) command (OPTXD) is transmitted from the MPU to the  
operation panel LSI in synchronization with the OPCLK signal. Once the LSI decodes the command, the  
command must pass a command code check and have no parity errors. Then, the specified I/O control  
will return the two byte command response to the MPU.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 37  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
2.1.07 Alarm Circuit  
Driver Circuit Alarm Processing  
The printhead driver output and the head gap magnet output drive signals are monitored at R29 and C8.  
The POWER OFF-P signal is output by the comparator (Location 02C: IC2901) when driven for more than  
the specified time. This signal becomes the ALM signal. The ALM signal is sent to the power supply board  
and causes the DC voltages to be turned off.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 38  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Low Motor Drive Voltage Alarm  
+40V is converted into the POWLEV signal (0 vdc to +5 vdc) by the voltage divider network of R542 and  
R544, then input to the A/D port of the MPU. The value of this voltage is used to control the drive time and  
the print speed (pass number) of the head.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 39  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Head Drive Time  
The head drive time is modified to compensate for the amount of the voltage drop of the POWLEV signal.  
By monitoring the voltage drop every 500 microseconds, the MPU is able to control and maintain the  
impact necessary for each printhead pin.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 40  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Print Speed  
Actual Voltage (+40 vdc)  
+34 vdc or greater  
+32 vdc to +34 vdc  
+30 vdc to +32 vdc  
+30 vdc or less  
Passes Required  
Relative Print Speed  
100%  
Approximately 85%  
Approximately 50%  
Less than 50%  
1
1
1
2
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 41  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Head Overheat Alarm Processing  
If the printhead temperature exceeds 110 degrees Celsius, the printer will switch to uni-directional print. If  
the temperature exceeds 118 degrees Celsius, printing will stop. Once the printhead cools, printing will  
resume.  
Two thermistors are used to monitor the printhead temperature. One is contained in the printhead. The  
other is in the printhead driver.  
A thermistor in the printhead prevents over-heating of the coil during periods of continuous bi-directional  
printing. If the temperature of the coil exceeds the pre-determined limits, the control circuit detects the  
thermistor signal (TSD).  
Another thermistor monitors the temperature of the printhead driver. If the temperature of the driver  
exceeds the pre-determined limits, the control circuit detects the thermistor signal (TSD).  
The voltage of the TSD signal is monitored at the MPU A/D port to control the pass number and print  
method (uni-directional / bi-directional) at each of seven levels.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 42  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
2.1.08 Power Supply Circuit  
The switching type power supply circuit supplies the +5 vdc, +/-8 vdc, 10 VAC and +40 vdc.  
Voltage/Signal  
+5 vdc  
Purpose  
IC logic levels, LED drive voltages  
+8 vdc  
+10 VAC  
+40 vdc  
Serial interface line voltage, comparator IC  
Serial interface line voltage and the printhead analog circuit  
Printhead, space motor and line feed motor drive voltage  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 43  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
2.2 MECHANICAL OPERATION  
2.2.01 Printhead Mechanism  
The printhead is a spring-charged, 9-pin printhead. It is attached to the carriage, which moves parallel to  
the platen. Electrically, the printhead is controlled by the main control board via the carriage cable and the  
space motor.  
The printhead is composed of the following parts.  
Wire Guide  
Spring Assembly  
Wire, Armature, Spring, Yoke, Spacer  
Magnet Assembly  
Magnet, Core, Coil, Yoke  
Printed Circuit Board  
Logic Control, Print Driver, Analog Sensor Control and Thermistor  
Cooling Fin  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 44  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Printhead Gap Information  
Three items factor into printhead gap information.  
1. Printhead Gap Adjustment  
This is a SERVICE ADJUSTMENT made by a technician.  
It is covered in Section 3.3 of this Service Handbook.  
The Adjustment measures 0.014, +/- 0.001 inches (0.35, +/- 0.03 mm).  
2. Printhead Gap Adjust  
This is a MENU ITEM in the SET-UP Group.  
It fine tunes the automatic setting of the printhead gap.  
The settings are 0, 1, and -1.  
0 is the factory default.  
Use 1 to darken print (if output is consistently light).  
Use - 1 to lighten print (if output is consistently dark).  
3. Gap Control  
This is a MENU ITEM in each [Paper Feed] Group.  
The Groups are REAR FEED, BOTTOM FEED, and TOP FEED.  
Gap Control determines how the printhead gap is set.  
The settings are listed below.  
Auto Gap, Semi Auto Gap, 1, 2, 3, 4, 5, 6, 7, 8, 9  
An explanation of each setting follows.  
Auto Gap  
This is the factory default.  
Automatically determines paper thickness of the first page.  
During single-sheet feed, each pages thickness is checked while a job is printing.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Semi Auto Gap  
Similar to Auto Gap.  
Automatically determines paper thickness of the first page.  
During single-sheet feed, each pages thickness IS NOT checked while a job is printing.  
1, 2, 3, 4, 5, 6, 7, 8, 9  
Used when the same paper is used ALL of the time.  
Bypasses the automatic head gap adjustment.  
1 is the narrowest gap setting.  
9 is the widest gap setting.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 45  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Interconnect Diagram: Control Board to Printhead  
NOTE:  
The printhead coil resistance values ARE NOT LISTED.  
The individual printwire control lines CANNOT be accessed on this printhead.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 46  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Line Feed Motor Resistance  
The resistance of each coil should be approximately 13 ohms.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 47  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Space Motor Resistance  
The resistance of each coil should be approximately 5 ohms.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 48  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Printhead Operation  
When the printhead is idle, the armature is attracted to the permanent magnet. The print wires, which are  
attached to each armature, are then concealed inside the wire guide.  
When a signal to print a character is received, current flows through a coil. The magnetic field generated  
by the coil opposes the magnetic field between the armature and the permanent magnet. The armature is  
then driven in the direction of the platen by the force of the armature spring. The print wire (which is  
attached to the armature) protrudes from the tip of the wire guide and strikes the paper through the ribbon.  
This prints a dot on the paper.  
As the armature gets closer to the electrode of the analog sensor, the capacitance between them  
increases and a small amount of current flows. This current is amplified and sent to the logic control LSI to  
indicate armature activity. In order to attain optimum drive time, this information is transferred to the MPU.  
The MPU continually modifies the head gap to maintain the optimum drive time condition.  
The analog sensor element monitors all of the pins. The difference in pin stroke due to the curvature of  
the platen is compensated for at the logic control section of the printhead and is not transferred to the  
MPU.  
After the character has been printed, the permanent magnet attracts the armature and the print wires are  
retracted into the wire guide.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 49  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Printhead Temperature  
If the printhead temperature exceeds 110 degrees Celsius, the printer will switch to uni-directional print. If  
the temperature exceeds 118 degrees Celsius, printing will stop. Once the printhead cools, printing will  
resume.  
Two thermistors are used to monitor the printhead temperature. One is contained in the printhead. The  
other is in the printhead driver.  
A thermistor in the printhead prevents over-heating of the coil during periods of continuous bi-directional  
printing. If the temperature of the coil exceeds the pre-determined limits, the control circuit detects the  
thermistor signal (TSD).  
Another thermistor monitors the temperature of the printhead driver. If the temperature of the driver  
exceeds the pre-determined limits, the control circuit detects the thermistor signal (TSD).  
The voltage of the TSD signal is monitored at the MPU A/D port to control the pass number and print  
method (uni-directional / bi-directional) at each of seven levels.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 50  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
2.2.02 Spacing Mechanism  
The spacing mechanism consists of a carriage shaft (mounted parallel to the platen), and a carriage  
frame which moves along the shaft. The carriage frame is driven by a DC servo motor mounted on the  
carriage frame.  
Items included in the spacing mechanism are listed below.  
Space Motor Assembly  
DC Servo Motor  
Motor Gear  
Sensor  
Encoder Disk  
Carriage Frame  
Carriage Shaft  
Space Rack  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 51  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Spacing Operation  
The carriage frame, which contains the printhead and space motor, moves along the carriage shaft  
parallel to the platen. When the space motor rotates, the driving force is transmitted to the motor gear. As  
the motor gear rotates, the carriage moves along the platen. For every revolution of the DC servo motor,  
the carriage frame moves 0.8 inch (20.32 mm).  
As the DC servo motor rotates, a slotted disk (called the encoder disk), rotates with the servo motor and  
passes through the photosensor. The position of the carriage frame can be determined by counting the  
pulses generated by the photosensors.  
In the same way, the rotation of the space motor can be recognized and controlled by measuring the  
phase relationship and the pulsewidth of the signals generated by the photosensors.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 52  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
2.2.03 Head Gap Mechanism  
The head gap is automatically set for the thickness of the medium loaded in the printer. In the case of  
envelopes, where the medium thickness varies as the printhead moves along the platen, the strike force  
of the pins changes to compensate for the differences in thickness.  
Head Gap Setting Operation  
Once printing starts, the space motor rotates the ribbon gear, causing idle gear C to turn the change gear.  
When the MPU requests a change in the head gap setting, the GAP-P signal causes the armature (which  
is holding the change gear) to be attracted to the pranger magnet. The gap reset spring can now push the  
change gear so it contacts the gap change gear.  
The rotation of the gap change gear causes idle gear D to turn the adjust gear. The adjust gear turns the  
adjusting screw, resulting in a new head gap setting.  
NOTE:  
As the adjusting screw turns counter-clockwise, the gap narrows.  
As the adjusting screw turns clockwise, the gap widens.  
There is a cam at each setting of the gap change gear. When the change gear is at the top of the cam,  
the change gear disengages from the gap change gear. At this time, the armature resets, changing the  
head gap by one setting.  
The head gap is modified in .06 mm units for each range setting.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 53  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Ribbon Drive Operation  
The ribbon drive mechanism feeds the ribbon in synchronization with the spacing operation. The force  
required to drive the ribbon is obtained from the space motor.  
The ribbon drive mechanism is composed of the items listed below.  
Ribbon Drive Gear Assembly  
Ribbon Gear  
This gear is located on the space motor assembly  
Ribbon Cartridge  
A continuous loop ribbon with uni-directional feed is used. Ink is supplied from an ink  
which is built into the ribbon cartridge.  
tank,  
When the space motor turns, the ribbon gear on the spacing motor shaft rotates. The rotation is  
transmitted via a combination of gears, from the ribbon drive gear assembly to the drive gear in the ribbon  
cartridge.  
Although the space motor moves in both the forward and reverse directions during bi-directional printing,  
the gears in the ribbon drive assembly maintain uni-directional ribbon feed by switching the rotation  
direction of the gears.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 54  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
2.2.05 Line Feed Mechanism  
The line feed operation is accomplished by activating the line feed motor which turns the platen.  
The rotation of the platen is used to feed paper from the selected paper path.  
The components of the paper feed mechanism are listed below.  
Line Feed Motor (pulse motor), with gears  
Line Feed Idler Gear  
Platen  
Rear Tractor Feed Unit  
Pressure Roller  
Change Lever (Paper Path Selection Lever)  
The change lever is used to select one of three different paper paths; top, rear or bottom.  
Paper Clamp Mechanism  
Moving the change lever between the bottom, top and rear positions, changes the positions of the front  
release gear arm and the release cam.  
The movement of the front release gear arm changes the position of the front release gear shaft. This  
causes the front pressure roller to open or close.  
The movement of the release cam causes the rear pressure roller to open or close.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 55  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Cut Sheet/Continuous Sheet Switching Mechanism  
Top Feed (for cut sheet paper)  
When cut sheet paper is used during normal operation or by the Cut Sheet Feeder (CSF) option, place the  
change lever in the Top Feed position.  
As the platen turns, the platen gear causes the idle gear to rotate.  
At this time, the rear and front pressure rollers are pressed securely to the platen to feed the cut sheet.  
The cut sheet detection lever enables the cut sheet detection switch (which is located on the main control  
board). This places the printer in the cut sheet mode.  
When cut sheet paper is placed between the platen and the paper chute, the printer automatically feeds  
the sheet to the print start position.  
Rear/Bottom Feed (for continuous feed paper)  
When the continuous feed paper is used, either with the rear tractor, optional bottom tractor or optional  
pull tractor, place the change lever in the Rear/Bottom Feed position.  
When the change lever is placed in this position, the reset spring pushes the change gear. In this position,  
the idle gear is engaged with the bottom tractor unit drive gear and the tractor gear. As the platen turns,  
power is transferred from the platen gear, to the idle gear, to the change gear, and then to the push tractor  
shaft.  
CAUTION:  
The cut sheet / continuous sensor lever must be positioned below the BASW sensor. The lever should  
contact the sensor only when the change lever is in the top feed (middle) setting.  
If the lever is not correctly positioned, the ALARM lamp will light and the unit will not automatically load  
paper or receive data.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 56  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Cut Sheet Paper Feed Operation  
As the line feed motor rotates, power is transferred through the decelerating gears (line feed idler gear,  
platen gear) to the platen.  
When using cut sheet paper, the change lever must be in the TOP position so the platen and pressure  
rollers can feed the paper. This also disengages the push tractor.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 57  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Continuous Paper Feed (Rear Tractor Mechanism)  
As the platen rotates, power is transferred to the tractor gear from the platen gear, the idler gear, and the  
change gear. The tractor gear drives the pin tractor belts, which feed the continuous paper.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 58  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Continuous Paper Feed (Pull Tractor Mechanism)  
Bottom feed of continuous sheets is possible only when an optional pull tractor unit is installed.  
As the platen rotates, power is transferred to the drive gear from the line feed idler gear, the platen gear,  
idler gear B and idler gear A. The drive gear turns the pull tractor assembly, which feeds the continuous  
paper.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 59  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Continuous Paper Feed (Bottom Tractor Feed Mechanism)  
As the platen rotates, power is transferred to the drive gear from the platen gear, the idle gear and the  
tractor change gear. The drive gear turns the pin tractor belts on the bottom tractor feed unit, which feeds  
the continuous paper.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 60  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Continuous Paper Feed (Push/Pull Tractor Mechanism)  
This mechanism consists of an optional pull tractor and a standard push tractor mechanism.  
Continuous paper is fed by these two tractors at the same time.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 61  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
2.2.06 Paper Detection Mechanism  
Top Feed Paper Detection  
When cut sheet paper is inserted into the printer, Point A of the Rear/Top Paper Feed Lever is pushed  
backward, causing the Sensor Lever to rotate.  
As the Sensor Lever rotates, it contacts the Rear Sensor Lever. This makes the Rear Sensor Lever rotate.  
The Rear Sensor Lever rotates, unblocking the Rear / Top Paper End Sensor (SNS1).  
Rear Feed Detection  
When paper is fed from the Rear Push Tractor, Point B is pushed backward. This makes the Sensor  
Lever rotate.  
As the Sensor Lever rotates, it contacts the Rear Sensor Lever. This makes the Rear Sensor Lever rotate.  
The Rear Sensor Lever rotates, unblocking the Rear / Top Paper End Sensor (SNS1).  
Bottom Feed Detection  
When the paper is fed from the bottom of the printer, Point C is pushed, rotating the Bottom Paper End  
Lever.  
As the Bottom Paper End Lever rotates, it contacts the Bottom Sensor Lever. This makes the Bottom  
Sensor Lever rotate.  
The Bottom Sensor Lever rotates, unblocking the Bottom Paper End Sensor (SNS2).  
NOTE:  
The method for detecting a paper-end condition is the reverse of the above.  
PAPER-END is detected when the Bottom Paper End Sensor (SNS2) is blocked.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 62  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
2.2.07 Support Protector Mechanism  
During printer initialization, the support protector is latched in the stored position (approximately 5 mm  
from the left bracket of the main frame).  
Just before paper is loaded, the printhead moves towards the left bracket and unlatches the support  
protector.  
As the printhead moves to the right, the support protector reset spring pushes the support protector  
toward the center of the platen. With the support protector in this position, the ribbon protector and the  
support protector prevent the leading edge of the paper from curling or folding.  
Once the paper is ejected, the printhead slowly moves towards the left bracket. The support protector is  
latched in the stored position when it is pushed to approximately 5 mm from the left bracket.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 63  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
2.2.08 Automatic Paper Load  
The Microline 520/521 printers will automatically detect cut sheet paper and feed the paper to the Top of  
Form (TOF) position.  
Cut Sheet Paper  
Set the change lever to the TOP FEED position.  
NOTE:  
When the change lever is in the TOP FEED position, the cut sheet detection lever contacts the cut sheet  
detection switch (BASW), which is located on the main control board.  
Insert the sheet of paper between the platen and the paper chute.  
Once paper is detected at the paper end sensor and the amount of time selected on the Wait Time setting  
of the menu has lapsed, the line feed motor will feed the paper until the leading edge of the paper reaches  
the top of form position.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 64  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
Continuous Feed Paper  
Set the change lever to either the REAR FEED or BOTTOM FEED position.  
NOTE:  
When the change lever is in the REAR FEED or BOTTOM FEED position, the cut sheet detection lever  
does NOT contact the cut sheet detection switch (BASW), which is located on the main control board.  
Place continuous feed paper in the appropriate tractor.  
Press the FF/LOAD switch.  
The line feed motor will feed the paper until the leading edge of the paper reaches the top of form position.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 65  
Service Guide ML520/521  
Chapter 2 Principles of Operation  
2.2.09 Paper Park  
If continuous feed paper is installed and printing on cut sheet paper is desired, it is not necessary to  
unload the continuous feed paper. The Paper Park feature provides a means of retracting the continuous  
feed paper from the paper path, while (at the same time) cut sheet paper is fed.  
Paper Park Operation  
Place the change lever in the REAR FEED or BOTTOM FEED position.  
Press the PARK switch on the operation panel.  
A reverse line feed operation retracts the paper until paper-end occurs or 19 inches of paper have been  
retracted.  
NOTE:  
Retracting 19 inches of paper without detecting a paper-end condition causes the line feed operation to  
stop. The line feed operation stops because the printer assumes a jam has occurred.  
The operator can press the SEL switch to reset the ALARM LED and press the PARK switch to continue  
the park operation.  
This operation may be useful when length of the paper to be parked is greater than 19 inches.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 66  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.1.01 General Information  
This section lists the parts replacement, adjustment, cleaning, lubrication, and shipping procedures.  
Disassembly should not be performed unless absolutely necessary. NEVER perform disassembly on a  
malfunctioning printer until you have followed the failure analysis procedures in Section Four of this  
Service Handbook.  
Follow the procedures listed in Adjustments and Service Settings. Adjustments may be required when  
either consumable or parts are replaced. Failure to perform these procedures could result in unnecessary  
service calls.  
Proper performance of maintenance and cleaning will help to achieve the best possible print quality from  
the printer.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 67  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.1.02 Maintenance Tools  
The following tools are required to service the printer.  
#2 Phillips Screwdriver (with magnetic tip)  
Straight-slot Screwdriver  
Needle Nose Pliers (4 Inch)  
Wire Cutters  
Digital Multimeter  
Feeler Gauge (capable of measuring .014 inches)  
Shop Vacuum  
Clean, soft, and lint-free Cloth  
All-Purpose Cleaner  
Contact Kleen (Okidata P/N 51802301)  
Platen Cleaner  
Machine Grease  
Machine Oil  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 68  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.1.03 Maintenance Precautions  
1. Do not disassemble the unit if it is operating normally.  
2. Before starting disassembly and assembly, always turn the AC power switch OFF and pull out the AC  
plug.  
3. Detach the interface cable, if installed.  
4. Do not remove parts unnecessarily. Try to keep disassembly to a minimum.  
5. Use the recommended maintenance tools.  
6. When disassembling, follow the listed sequence. Failure to follow the correct sequence may result in  
damaged parts.  
7. Since screws, collars and other small parts are easily lost, they should be temporarily attached to the  
original positions.  
8. When handling circuit boards use extreme care. Integrated circuits (microprocessors, ROM, and  
RAM) can be destroyed by static electricity.  
9. Do not place printed circuit boards directly on conductive surfaces.  
10. Follow the recommended procedures when replacing assemblies and units.  
11. Perform the printhead gap adjustment procedure (Refer to Section 3.3 of this Service  
Handbook) when the any of the following occur.  
Print Quality is darker on one side of the document.  
Parts are replaced  
Printhead (3.2.02)  
Space Motor Assembly (3.2.11)  
Space Rack (3.2.13)  
Guide Rail (3.2.15)  
Platen Assembly (3.2.19)  
Carriage Shaft (3.2.25)  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 69  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2 DISASSEMBLY/ASSEMBLY PROCEDURES  
General Information  
This section contains the printer disassembly procedures. Only the removal procedures are explained  
here. Reverse the procedure for the installation.  
At the bottom of each procedure is a listing of the parts covered in that procedure. The Okidata part  
number, item description, comment (RSPL, Option, Consumable) and cross-reference to Appendix B is  
provided for each part. Items included in the Recommended Spare Parts List are indicated by the acronym  
RSPL. N/A will appear where a part number is not available.  
520 indicates that the item is specific to the Microline 520.  
521 indicates that the item is specific to the Microline 521.  
Both indicates that the item is common to both printers.  
This Service Handbook lists the disassembly procedures for major components of the unit. Okidata DOES  
NOT recommend disassembling a unit which is operating normally. If you decide to perform disassembly  
during this training, Okidata recommends that you perform only the disassembly procedures for RSPL  
items. All other procedures are provided to assist you in identifying parts. It is not likely that you will  
perform these procedures while servicing the unit.  
Be sure to read all notes, cautions, and warnings, as they contain important information regarding  
disassembly / assembly.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 70  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.01 Preliminary Items  
1. Press the AC switch (1) and power off the printer.  
2. Remove the paper, if installed (2).  
3. Detach the AC power cord (3).  
4. Detach the interface cable, if installed (4).  
P/N 56609701 Cord: AC RSPL Both B.2.03  
P/N 56624101 Cord: AC 220V (ML Series) Right Angle Option RSPL Both B.2.03  
P/N 56624401 Cord: AC 240V Option RSPL Both B.2.08  
P/N 70000803 Kit: Parallel Interface Option Both B.2.08 Plug n Play Accessory  
P/N 70012801 Kit: RS232-C Serial Interface Option Both B.2.08  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 71  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.02 Printhead Assembly  
1. Perform this procedure: 3.2.01.  
2. Open the access cover (1).  
3. Lift and remove the ribbon. (Not shown)  
4. Pull the head clamp (2) towards the right and then rotate it up to release the printhead (3).  
5. Pull the printhead straight up to remove it.  
NOTE:  
Installation After installing the printhead, check the printhead gap adjustment. Refer to Section 3.3 of  
this Service Handbook.  
P/N 52107001 Ribbon: Black Consumable Both B.2.10  
P/N 50707401 Clamp: Head RSPL Both B.2.07  
P/N 50099501 Assembly: Printhead RSPL Both B.2.03  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 72  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.03 Ribbon Protector  
CAUTION  
You MUST use a straight slot screwdriver to release the ribbon protector. If you attempt to lift the protector  
without releasing the tabs, the protector will break.  
.
1. Perform these procedures: 3.2.01 , and 3.2.02  
2. Open the pull-up roller cover (1).  
3. Use a straight-slot screwdriver to release the extensions (2) from the carriage frame set (3).  
4. Lift the ribbon protector (4) straight up and remove it.  
P/N 53562801 Protector: Ribbon RSPL Both B.2.07  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 73  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.04 Gear Case Assembly  
1. Perform these procedures: 3.2.01 , and 3.2.02  
.
2. Use a straight-slot screwdriver to release the four claws (1) of the gear case assembly (2).  
3. Lift and remove the gear case assembly.  
NOTE:  
When lubricating, refer to Section 3.5 of this Service Handbook.  
Lubrication ---  
P/N 51228501 Gear: Case (Assembly) RSPL Both B.2.07  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 74  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.05 Pull-up Roller Assembly  
1. Perform this procedure: 3.2.01.  
2. Open the access cover (1).  
3. Open the cover of the pull-up roller assembly (2).  
4. Press at A while rotating the assembly towards the back of the printer.  
5. Remove the assembly.  
NOTE: Lubrication  
When lubricating, refer to Section 3.5 of this Service Handbook.  
P/N 53341501 Roller: Pull Up Assembly (Narrow) RSPL 520 B.2.05  
P/N 53341601 Roller: Pull Up Assembly (Wide) RSPL 521 B.2.05  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 75  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.06 Upper Cover, Access Cover, and Sheet Guide Assemblies  
1. Perform this procedure: 3.2.01.  
2. Pull the platen knob (1) straight out and remove it.  
3. Set the change lever (2) to the bottom feed position (toward the rear of the printer).  
4. Insert a flat-blade screwdriver into the grooves (3) of the frame and pry the upper cover (4) away from  
the frame.  
5. Raise the front side of the upper cover assembly.  
6. Tilt the upper cover assembly toward the rear to disengage the claws (not shown) at the rear of the  
frame.  
7. Lift the upper cover assembly and remove it.  
CAUTION:  
Do not rotate the access cover past the vertical when removing it or you will break the tab extensions.  
8. Raise the access cover assembly (5) until it is vertical, then lift it straight up to remove it.  
9. Remove the sheet guide assembly (6).  
10. Note the position of the cover (B) [for card slot] (7). This is part of the upper cover and should not be  
removed. No font cards are currently available.  
CAUTION:  
When installing the upper cover, make sure that the sensors correctly contact the control board (3.2.07).  
The cut sheet/continuous sensor lever must be positioned below the BASW sensor. The lever should  
contact the sensor only when the change lever is in the top feed (middle) setting. If the lever is not  
correctly positioned, the ALARM lamp will light and the unit will not automatically load paper or receive  
data.  
When cleaning, refer to Section 3.4 of this Service Handbook.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
P/N 51009401 Guide: Sheet (Narrow) RSPL 520 B.2.02  
P/N 51009501 Guide: Sheet (Wide) RSPL 521 B.2.02  
P/N 53066902 Cover: Upper (Narrow) RSPL 520 B.2.02  
P/N 53067002 Cover: Upper (Wide) RSPL 521 B.2.02  
P/N 53067101 Cover: Access (Narrow) RSPL 520 B.2.02  
P/N 53067201 Cover: Access (Wide) RSPL 521 B.2.02  
P/N 53067301 Cover: (B) for card slot RSPL Both B.2.03  
P/N 53562601 Knob: Platen (ML500 Series) RSPL Both B.2.03  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 76  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.07 Control Board (FJIM)  
1. Perform these procedures: 3.2.01 , and 3.2.06  
2. Remove the two screws (1).  
.
3. Release the control board (2) from the bracket (3).  
4. Tilt the board to access the connectors.  
5. Detach connectors CN6 - operator panel (4), CN7- carriage cable (5), CN3 - power supply (6), and CN5  
- line feed motor (7).  
6. Remove the board.  
NOTE:  
Installation  
The bottom sensor lever must be positioned in the SNS3 sensor (8).  
The rear sensor lever must be positioned in the SNS1 sensor (9).  
The cut sheet/continuous sensor lever must be positioned below the BASW sensor (10). The lever should  
contact the sensor only when the change lever is in the top feed (middle) setting.  
If the lever is not correctly positioned, the ALARM lamp will light and the unit will not automatically load  
paper or receive data.  
The IC: EEPROM is soldered in on the board.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
P/N 55072401 PCB: FJIM (w/o ROM) RSPL Both B.2.03  
P/N 55938301 IC: EEPROM BR93CC46A RSPL Both B.2.03  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 77  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.08 Power Supply Assembly  
1. Perform these procedures: 3.2.01 and 3.2.06  
.
2. Use a straight slot screwdriver to detach the claws from both sides of the cable clamp (1).  
3. Remove the cable clamp (2).  
4. Detach the transformer cable from connector CN3 (3) of the control board (4).  
5. Detach the cable from the connector (5) of the filter board (6).  
6. Use a straight slot screwdriver to free the transformer from the holding clamp (A), position the  
screwdriver in the direction of the arrow (7) twist the screwdriver while pushing the transformer (8) towards  
the control board .  
7. Lift and remove the transformer assembly.  
8. Remove the screw (9) from the ground wire of the filter board.  
9. Use a straight slot screwdriver to detach the claw (10), tilt the filter board upward, then work the AC inlet  
and the AC switch free.  
10. Lift and remove the filter board assembly.  
NOTE:  
When installing, verify that the AC inlet and AC switch are oriented correctly.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
P/N 56412401 Transformer: 120 V ML520 RSPL 520 B.2.03  
P/N 56412402 Transformer: 120 V ML521 RSPL 521 B.2.03  
P/N 55073201 PCB: Filter 120 V RSPL Both B.2.03  
P/N 50707501 Clamp: Cord RSPL Both B.2.03  
P/N 56306201 Fuse: 1A 250V (Filter Brd 220V) Option RSPL Both B.2.03  
P/N 56306101 Fuse: 2.5A 125V (Filter Board) RSPL Both B.2.03  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 78  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.09 Operator Panel PCB (LEOP)  
1. Perform these procedures: 3.2.01 , 3.2.06 , and 3.2.07  
2. Cut the nylon tie and release the cable. (Not shown)  
3. Disengage the claws (1) on both sides of the frame.  
.
4. Lift the operator panel assembly (2) straight up and remove it.  
5. Open eight claws (3) and remove the operator panel board (4) from the operator panel (5).  
P/N 53562703 Panel: Operator RSPL Both B.2.03  
P/N 55937502 PCB: LEOP (Operator Panel) RSPL Both B.2.03  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 79  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.10 PC Connector  
1. Perform these procedures: 3.2.01 , 3.2.02 , and 3.2.04  
.
2. Remove the two screws (1) and the connector holders. The holders are not shown.  
3. Remove the PC connector (2).  
NOTE:  
Installation  
Do not touch the contacts of the PC connector.  
Do not touch the contacts of the space motor (3).  
Cleaning  
When cleaning, refer to Section 3.4 of this Service Handbook.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
P/N 56729601 Connector: PC HD40 RSPL Both B.2.07  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 80  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.11 Space Motor and Roller Guide Assemblies  
1. Perform these procedures: 3.2.01 , 3.2.02 , 3.2.04 , and 3.2.10  
2. Remove the three screws (1).  
.
3. Lift the space motor assembly (2).  
4. Remove the left (3) and right connector holders (4).  
5. Remove the roller guide assembly (5) and guide roller spring (6).  
6. Use firm pressure to pull the carriage cable (7) out to detach the cable from the space motor  
assembly.  
7. Remove the space motor assembly.  
NOTE:  
The guide roller assembly includes the guide roller (8), the guide roller holder (9), and the pin (10).  
Installation: Position the guide roller assembly first.  
The contact side of the cable faces down when the carriage cable is inserted into the connector on the  
space motor assembly. Work the cable from side to side until it is fully seated in the connector. No  
contacts should be visible.  
After installing the space motor assembly, check the printhead gap adjustment. Refer to Section  
3.3 of this Service Handbook.  
When lubricating, refer to Section 3.5 of this Service Handbook.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
P/N 53343001 Holder: Connector (L) RSPL Both B.2.07  
P/N 53343101 Holder: Connector (R) RSPL Both B.2.07  
P/N 56510401 Motor: Space Assembly RSPL Both B.2.07  
P/N 53343301 Guide: Roller Assembly Both B.2.07  
P/N 53341901 Roller: Guide RSPL Both B.2.07  
P/N 53342001 Holder: Guide Roller RSPL Both B.2.07  
P/N N/A Pin Both B.2.07  
P/N N/A Guide Roller Spring Both B.2.07  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 81  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.12 Carriage Cable  
1. Perform these procedures: 3.2.01 , 3.2.06 , 3.2.07 , and 3.2.11  
.
2. Slightly bow the carriage cable (1) to release it from the claws (2) and the projection on the main  
frame (3).  
3. Remove the carriage cable guide (4).  
4. Remove the carriage cable.  
NOTE:  
Installation  
The contacts on the cable face up when the cable is positioned on the main frame.  
The cable end with the 45° angled contacts connects to the gear case assembly.  
Do NOT sharply bend the carriage cable. You will slightly bow the cable to position it under the claws  
and over the projection.  
P/N 56627301 Cable: Carriage (Narrow) RSPL 520 B.2.07  
P/N 56627302 Cable: Carriage (Wide) RSPL 521 B.2.07  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 82  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.13 Space Rack  
1. Perform these procedures: 3.2.01 , 3.2.02 , 3.2.04 , 3.2.10 , and 3.2.11  
.
2. Remove the spring (1).  
3. Disengage the claws (2) on the both ends of the space rack (3).  
4. Pull the space rack straight up and remove it.  
NOTE:  
Installation  
After installing the space rack, check the printhead gap adjustment. Refer to Section 3.3 of this  
Service Handbook.  
Cleaning  
When cleaning, refer to Section 3.4 of this Service Handbook.  
CAUTION  
Do NOT lubricate the space rack. Lubricating the space rack will attract dust. If enough dust  
accumulates on the space rack, printing problems will occur.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
P/N 50923501 Spring: Tension (Space Rack) RSPL Both B.2.04  
P/N 53563301 Rack: Space (Narrow) RSPL 520 B.2.04  
P/N 53563401 Rack: Space (Wide) RSPL 521 B.2.04  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 83  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.14 Roller/Holder Backup Assembly  
1. Perform these procedures: 3.2.01 , 3.2.02 , 3.2.04 , 3.2.10 , and 3.2.11  
.
2. Use a small straight slot screwdriver to disengage the claws of the backup roller holder spring (1) from  
the carriage frame (2).  
3. Remove the roller/holder backup assembly (3).  
NOTE:  
The roller/holder backup assembly includes the backup roller (4), the backup roller holder (5), and the  
pin (6).  
P/N 53343201 Assembly: Roller/Holder Backup Both B.2.07  
P/N 53341701 Roller: Back Up RSPL Both B.2.07  
P/N 53341801 Holder: Back Up Roller RSPL Both B.2.07  
P/N N/A Pin Both B.2.07  
P/N 50925001 Backup Roller Holder Spring Both B.2.07  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 84  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.15 Guide Rail and Adjust Cam  
1. Perform these procedures: 3.2.01 , 3.2.02 , 3.2.04 , 3.2.10 , 3.2.11 , and 3.2.14  
2. Rotate the adjust cam (1) in the direction of arrow A as far as possible.  
3. Pull the cam out and remove it.  
.
4. Carefully press the claw (2 location only) in the base frame down to release the guide rail (3). Do not  
press too hard or the claw will break.  
5. Use a straight slot screwdriver to slide the guide rail in direction of arrow A.  
6. Lift the guide at position B and work the other end of the guide free to remove the guide rail.  
7. Remove the ground clip (4)  
NOTE:  
Installation After installing the guide rail, check the printhead gap adjustment. Refer to Section  
3.3 of this Service Handbook.  
P/N 51009701 Guide: Rail Ground Clip RSPL Both B.2.04  
Download from Www.Somanuals.com. All Manuals Search And Download.  
P/N 51009801 Guide: Rail (Narrow) RSPL 520 B.2.04  
P/N 51009901 Guide: Rail (Wide) RSPL 521 B.2.04  
P/N 53067701 Cam: Adjust RSPL Both B.2.04  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 85  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.16 Left Ground Plate  
1. Perform these procedures: 3.2.01 , 3.2.06 , and 3.2.07  
2. Cut the nylon tie and release the cable. (Not shown).  
3. Work the left ground plate (1) up, and then out, to remove it.  
.
P/N 51010301 Plate: Left Ground RSPL Both B.2.04  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 86  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.17 Right Ground Plate  
1. Perform these procedures: 3.2.01 , and 3.2.06  
.
2. Pull the top tabs (1) of the right ground plate (2) out to free the plate from the claws of the base frame.  
You may have to use a screwdriver to work the plate tabs free.  
3. Lift the plate and remove it.  
NOTE:  
Installation The plate must be securely seated under the claws.  
P/N 51010201 Plate: Right Ground RSPL Both B.2.05  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 87  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.18 Rear and Cut Sheet Paper Feed Sensor Levers  
1. Perform these procedures: 3.2.01 , 3.2.06 , 3.2.07 , 3.2.16 , and 3.2.20  
.
2. Turn the cut sheet/continuous feed paper sensor lever (1) until the flag is at the top, then work the  
lever free.  
3. Remove the lever.  
4. Turn the rear feed paper sensor lever (2) until the flag is at the top, then work the lever free.  
5. Remove the lever.  
P/N 50804902 Lever: Sensor RSPL Both B.2.04 Cut Sheet/Continuous  
P/N 50804801 Lever: Rear Sensor RSPL Both B.2.04  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 88  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.19 Platen Assembly  
1. Perform these procedures: 3.2.01 , and 3.2.06  
.
2. Move the change lever (1) to the bottom feed position (to the rear of the printer).  
3. Push the lock levers (2) in, then rotate them towards the front to unlock them from the frame.  
4. The levers should be vertical.  
5. Lift the platen assembly (3) straight up and remove it.  
NOTE:  
Installation  
After installing the platen assembly, check the printhead gap adjustment. Refer to Section 3.3 of  
this Service Handbook.  
Cleaning  
When cleaning, refer to Section 3.4 of this Service Handbook.  
Lubrication  
When lubricating, refer to Section 3.5 of this Service Handbook.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
P/N 50098301 Platen Assembly (Narrow) RSPL 520 B.2.05  
P/N 50098302 Platen Assembly (Wide) RSPL 521 B.2.05  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 89  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.20 Paper Chute Assembly  
1. Perform these procedures: 3.2.01 , 3.2.06 , and 3.2.19  
.
2. Remove the rear pressure roller (1).  
3. Use a straight slot screwdriver to release the claws of the lock spring (2) and remove the spring.  
4. Remove the paper chute assembly (3).  
NOTE:  
The paper chute assembly includes the levers for the rear and top paper feed paths.  
P/N 53341301 Roller: Pressure Rear (Narrow) RSPL 520 B.2.06  
P/N 53341401 Roller: Pressure Rear (Wide) RSPL 521 B.2.06  
P/N 50924701 Spring: Lock RSPL Both B.2.06  
P/N 50097701 Paper Chute Assembly N RSPL 520 B.2.06  
P/N 50097801 Paper Chute Assembly W RSPL 521 B.2.06  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 90  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.21 Line Feed Motor Assembly  
1. Perform these procedures: 3.2.01 , 3.2.06 , 3.2.07 , 3.2.16 , 3.2.19 , 3.2.20, and 3.2.21 (this  
section).  
2. Firmly press down on the line feed motor assembly (1) while tilting the assembly out.  
3. Remove the line feed motor assembly.  
4. Remove the line feed connection cord (2).  
CAUTION:  
The line feed idle gear (3) should be removed only if it must be replaced. The claws will break when the  
gear is removed. A new gear must be installed.  
P/N 51228401 Gear: Line Feed Idle RSPL Both B.2.04  
P/N 56510301 Motor: Line Feed (Assembly) RSPL Both B.2.04  
Download from Www.Somanuals.com. All Manuals Search And Download.  
P/N 56627201 Cord: Connection Line Feed RSPL Both B.2.04  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 91  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.22 Reset Spring  
CAUTION:  
Please read through this entire procedure before performing it.  
Do not press against the vertical extensions of the reset spring at any time during this procedure.  
Firm pressure will release the spring, not brute force.  
1. Perform these procedures: 3.2.01 , 3.2.06 , and 3.2.17  
.
2. Place the right side of the unit over the edge of your work surface. You must be able to access the  
bottom of the unit. You will be working underneath and above the reset spring (1) at the same time.  
3. Reach from underneath the unit and press up at the extension (A) to free the spring from the claw.  
4. While pressing up, slide the spring out (in the direction of Arrow B) and remove it.  
P/N 50923201 Spring: Reset RSPL Both B.2.05  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 92  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.23 Idle Gear and Change Lever  
1. Perform these procedures: 3.2.01 , 3.2.06 , 3.2.07 , 3.2.16 , 3.2.17 , 3.2.19 , 3.2.20 , and  
3.2.22  
.
2. Remove the idle gear (1). The idle gear is a large narrow gear.  
3. Release the claw (2) of the change lever (3). The claw is accessed from inside the unit.  
4. Remove the change lever.  
NOTE:  
Lubrication When lubricating, refer to Section 3.5 of this Service Handbook.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
P/N 50805101 Lever: Change RSPL Both B.2.05  
P/N 51228201 Gear: Idle RSPL Both B.2.05  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 93  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.24 Pressure Spring  
1. Perform these procedures: 3.2.01 , 3.2.06 , 3.2.07 , 3.2.16 , 3.2.17 , 3.2.19 , 3.2.20  
3.2.22, and 3.2.23  
,
.
2. Turn the front release gear arm (1) until it is disengaged.  
3. Remove the release cam (2). This is the medium size, thick cam.  
4. Work the end of the pressure spring (3) free and remove the spring.  
5. Remove the front release gear arm. This arm is long, with a serrated edge.  
6. Remove the switch lever (4). This is the small lever.  
NOTE:  
Installation  
Install the release cam first.  
Then, install one end of the pressure spring into the release cam.  
Slide the cam and spring away from the base frame until the opposite end of the spring can be installed  
into the frame.  
Make sure that the front release gear arm is engaged as shown (A).  
Lubrication  
When lubricating, refer to Section 3.5 of this Service Handbook.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
P/N 50805201 Lever: Switch RSPL Both B.2.06  
P/N 50805301 Cam: Release RSPL Both B.2.05  
P/N 50923301 Spring: Pressure (Narrow) RSPL 520 B.2.06  
P/N 50923401 Spring: Pressure (Wide) RSPL 521 B.2.06  
P/N 51228301 Arm: Front Release Gear RSPL Both B.2.06  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 94  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.25 Carriage Shaft  
CAUTION  
The space motor assembly, etc. may be left in place when removing the carriage shaft. However, use  
extra care when doing so.  
The carriage cable should be detached from the space motor before removing the carriage shaft.  
1. Perform these procedures: 3.2.01 , 3.2.06 , 3.2.07 , and 3.2.16  
.
2. Push the end (A) of the carriage shaft (1) until it clears the base frame.  
3. Pull the carriage shaft free of the base frame.  
4. Remove the support protect reset spring (2).  
5. Remove the support protector assembly (3).  
6. Remove the frame set carriage (4).  
NOTE:  
Installation After installing the carriage shaft, check the printhead gap adjustment. Refer to Section 3.3  
of this Service Handbook. Cleaning When cleaning, refer to Section 3.4 of this Service  
Handbook. Lubrication When lubricating, refer to Section 3.5 of this Service Handbook.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
P/N 50098901 Carriage: Frame Set RSPL Both B.2.07  
P/N 50923601 Spring: Support Protect Reset RSPL Both B.2.04  
P/N 53067601 Protector: Support (Assembly) RSPL Both B.2.04  
P/N 53563501 Shaft: Carriage (Narrow) RSPL 520 B.2.04  
P/N 53563502 Shaft: Carriage (Wide) RSPL 521 B.2.04  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 95  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.26 Leaf Spring  
1. Perform these procedures: 3.2.01 , 3.2.06 , 3.2.07 , 3.2.16 , and 3.2.25  
.
2. Position the unit so you can access the top and bottom of the leaf spring (1).  
3. Start at one end of the spring.  
4. Use a straight slot screwdriver to release the bottom extension (2) from the claw of the base frame.  
5. Pull the spring up to release the top of the spring from the upper claw.  
6. Repeat the above two steps, working towards the opposite end of the spring.  
7. Remove the spring.  
P/N 50923001 Spring: Leaf (Narrow) RSPL 520 B.2.04  
P/N 50923101 Spring: Leaf (Wide) RSPL 521 B.2.04  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 96  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.27 Bottom Paper Sensor Levers  
1. Perform these procedures: 3.2.01 , 3.2.06 , 3.2.07 , 3.2.16 , 3.2.17 , 3.2.19 , 3.2.20  
3.2.22 , 3.2.23 , and 3.2.24  
,
.
2. Working from the underside of the unit, release the claws of the paper pan (1). When you release a  
claw, push on the claw to move the paper pan away from the main frame.  
3. Remove the pan.  
4. Rotate the bottom sensor lever (2) until the flag is at the top. Then, lift the lever and work it free of the  
frame to remove it. This lever has a box end.  
5. Remove the bottom paper end lever (3).  
6. Work the front release gear shaft (4) free of the tabs and remove it.  
NOTE:  
Lubrication When lubricating, refer to Section 3.5 of this Service Handbook.  
P/N 50097301 Pan: Paper (Narrow) RSPL 520 B.2.06  
P/N 50097401 Pan: Paper (Wide) RSPL 521 B.2.06  
P/N 50804601 Lever: Bottom Paper End RSPL Both B.2.04  
Download from Www.Somanuals.com. All Manuals Search And Download.  
P/N 50804701 Lever: Bottom Sensor RSPL Both B.2.04  
P/N 51227801 Shaft: Front Release Gear RSPL 520 B.2.06 (Narrow)  
P/N 51227901 Shaft: Front Release Gear (Wide) RSPL 521 B.2.06  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 97  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.28 Front Pressure Roller Assembly  
1. Perform these procedures: 3.2.01 , 3.2.06 , 3.2.07 , 3.2.16 , 3.2.17 , 3.2.19 , 3.2.20  
3.2.22 , 3.2.23 , and 3.2.24 , 3.2.27  
,
.
2. Separate the arms of the front roller holders (1) and remove the front pressure roller (2).  
3. Squeeze the extensions of the front roller holders together and remove the holders.  
4. Lift and remove the front pressure springs (3A and 3B).  
NOTE:  
The front pressure springs for the Microline 520 (3A) have three extensions. The front pressure springs  
for the Microline 521 (3B) have one extension. The Microline 521 uses both springs.  
Lubrication When lubricating, refer to Section 3.5 of this Service Handbook.  
P/N 50922901 Spring: Front Pressure (Narrow) RSPL 520 B.2.06  
P/N 50922801 Spring: Front Pressure (Wide) RSPL 521 B.2.06  
P/N 53341101 Holder: Front Roller RSPL Both B.2.06  
P/N 53341202 Roller: Front Pressure RSPL Both B.2.06  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 98  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.29 Tractor Assembly  
1. Perform these procedures: 3.2.01 , 3.2.06 , 3.2.07 , 3.2.16 , 3.2.17 , 3.2.19 , 3.2.20  
3.2.22 , 3.2.23 , and 3.2.24  
,
.
2. Use a needle nose pliers to release the claw of the tractor gear (1) and remove the gear.  
3. Remove the change gear (2).  
4. Raise the lock levers (3) on the left (4) and right (5) tractor assemblies.  
5. Slide the lower tractor feed shaft (6) in the direction of arrow A and remove the shaft. This shaft is  
square.  
6. Slide the upper tractor feed shaft (7) in the direction of arrow A and remove the shaft. This shaft is  
round.  
7. Remove the left tractor assembly, the guide (8), and the right tractor assembly.  
NOTE:  
Installation The tractors must be synchronized. Align the synchronization marks (9) in the same  
direction.  
Verify that the guide holes (10) in the tractor drive gears are facing the same direction.  
The left tractor assembly must be positioned to the left (line feed motor side) of the plastic tab and  
ground plate. Lubrication When lubricating, refer to Section 3.5 of this Service Handbook.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
P/N 50097501 Tractor: Assembly (Narrow) RSPL 520 B.2.06  
P/N 50097502 Tractor: Assembly (Wide) RSPL 521 B.2.06  
P/N 51228001 Gear: Change RSPL Both B.2.05  
P/N 51228101 Gear: Tractor RSPL Both B.2.05  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 99  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.2.30 Main Frame  
1. All disassembly procedures must be carried out to reach the base frame (1).  
P/N 53563101 Frame: Main (Narrow) RSPL 520 B.2.04/5/6  
P/N 53563201 Frame: Main (Wide) RSPL 521 B.2.04/5/6  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 100  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.3 PRINTER ADJUSTMENTS  
3.3.01 General Information  
This section contains the procedures for performing adjustments on the printer. These procedures may be  
required when replacing either consumables or parts. The disassembly/assembly procedures list the  
required adjustments and refer you to this section. Failure to perform these procedures may result in  
unnecessary service calls.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 101  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.3.02 Printhead Gap Adjustment  
General Information  
Before performing this adjustment, always verify that the printhead is properly installed. This adjustment  
should be performed when the following parts are replaced.  
1. Printhead (3.2.02)  
2. Space Motor Assembly (3.2.11)  
3. Space Rack (3.2.13)  
4. Guide Rail (3.2.15)  
5. Platen Assembly (3.2.19)  
6. Carriage Shaft (3.2.25)  
NOTE:  
Place a new ribbon cartridge in the printer before testing for parallelism.  
If the density of the top portion of the characters differ from that of the bottom portion, follow steps 10 -  
12.  
This adjustment is comprised of four phases.  
1. Setup Phase  
Steps 1-5  
The cover is removed and the printhead is placed at a known reference point.  
2. Printhead Gap Modification Phase  
Steps 6 - 10  
The distance between the printhead and the platen (at the left side of the platen) is modified by turning  
the adjust screw which varies the vertical position of the space motor.  
3. Parallel Adjustment Phase  
Steps 11 - 12  
The adjust cam lever is moved to ensure the printhead moves parallel to the platen.  
4. Verification Phase  
Steps 13 -14  
Verifies that the parallel adjustment phase did not affect the printhead gap modification phase.  
Procedure  
Setup Phase  
Download from Www.Somanuals.com. All Manuals Search And Download.  
1. Remove the upper cover and pull roller assembly.  
2. Move the change lever to the rear paper feed position.  
3. Rotate the platen.  
4. Set the gap change gear (Figure 1 A) to Range 2 by turning the adjust screw using a small phillips  
screwdriver. Turn this screw slowly while moving the carriage (1) to the left (if turning the screw  
counter clockwise) or (2) to the right (if turning the screw clockwise). This will allow easier rotation of  
the gears and prevent the gears from being stripped.  
DO NOT DISENGAGE THE ADJUST GEAR!  
5. Remove the ribbon protector.  
Printhead Gap Modification Phase  
6. Slide the carriage assembly to the left side of the platen.  
7. Check the printhead gap. Use a 0.014 inch or 0.35 mm feeler gauge. The printhead gap must  
measure 0.014 +/- 0.001 inch (0.35 +/- 0.03 mm).  
8. Use a large, straightened paper clip (Figure 1 B) to push down on the adjust gear. This will disengage  
the adjust gear from idle gear D.  
9. Use a small phillips screwdriver to turn the adjust screw. (Figure 1 C)  
Turning the screw CLOCKWISE will increase the printhead gap.  
Turning the screw COUNTERCLOCKWISE will decrease the gap.  
10. Slide the carriage assembly to the right side of the platen.  
Parallel Adjustment Phase  
11. Check the printhead gap at the right side of the platen.  
12. If the gap measurements are different between the left and right positions, turn the adjust cam as  
follows. (Figure 2 B)  
Turning the cam CLOCKWISE will increase the printhead gap.  
Turning the cam COUNTERCLOCKWISE will decrease the printhead gap.  
Verification Phase  
13. Check the printhead gap adjustment at the left, right, and center of the platen.  
14. If the printhead gap is not the same at all three positions, return to step 6.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 102  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.3.03 Key Combinations  
Key Combinations  
SEL + LF  
(Hold during Power-ON)  
SEL  
(Hold during Power-ON)  
QUIET + FF/LOAD  
(Hold during Power-ON)  
QUIET  
Description  
Reset Menu to Factory Defaults.  
Access Menu (if Menu set to LIMITED OPERATION)  
Reset Top of Form to Factory Default (1 inch)  
Activate Rolling ASCII Test  
(Hold during Power-ON)  
LF  
Activate Font Test  
(Hold during Power-ON)  
SEL + FF/LOAD  
(Hold during Power-ON)  
Activate Hexadecimal Dump Test  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 103  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.3.04 Menu Operation  
General Information  
The menu is used to customize the printers settings and features.  
The Menu is made up of a number of Groups.  
Each Group has a list of Items.  
Each Item has several Settings.  
Menu Mode  
To place the printer in the Menu Mode, follow this procedure.  
1. Verify that continuous feed paper is installed.  
2. Verify that the ribbon is correctly installed.  
3. Verify that the width of the installed paper matches the paper width menu setting.  
CAUTION:  
If the Menu is set for wide paper, and narrow paper is used, the printhead will print on the platen. This  
could damage / destroy the printhead, platen, and ribbon.  
4. Press and hold the SHIFT switch while pressing the SEL switch.  
5. The MENU lamp will light. If the printer was selected, the SELECT lamp will light.  
When in Menu Mode, the functions printed below the operator panel switches are active.  
6. Press GROUP until the desired Group prints.  
7. Press ITEM until the desired Item prints.  
8. Press SET until the desired Setting prints.  
9. Press EXIT to save the change and exit Menu Mode.  
Printing the Menu  
Printing the Menu provides a reference of current menu settings.  
This will help you move through the menu.  
Okidata STRONGLY RECOMMENDS printing the Menu before resetting the Menu to factory defaults.  
Once the Menu is reset, all customized settings are LOST.  
To print the Menu, follow this procedure.  
1. Verify that continuous feed paper is installed.  
2. Verify that the ribbon is correctly installed.  
3. Verify that the width of the installed paper matches the paper width menu setting.  
CAUTION:  
If the Menu is set for wide paper, and narrow paper is used, the printhead will print on the platen. This  
Download from Www.Somanuals.com. All Manuals Search And Download.  
could damage / destroy the printhead, platen, and ribbon.  
4. Press and hold the SHIFT switch while pressing the SEL switch.  
5. The MENU lamp will light. If the printer was selected, the SELECT lamp will light.  
When in Menu Mode, the functions printed below the operator panel switches are active.  
6. Press the PRINT switch.  
7. The Menu will print.  
8. Press EXIT to exit Menu Mode.  
For more information regarding the menu, please refer to the Printer Handbook.  
Reset Menu to Factory Defaults  
CAUTION:  
Once the menu has been reset, all customized menu settings will be lost.  
Always print the menu before resetting the printer to factory defaults.  
To reset the menu to factory default settings:  
1. Before resetting the Menu, Okidata STRONGLY RECOMMENDS printing the Menu.  
Printing the Menu provides a reference of customized settings.  
When the Menu is reset, all customized settings are LOST.  
2. Power off the printer.  
3. Press and hold SEL and LF while powering ON the printer.  
Limited Operation  
General Information  
One of the menu selections that may be set by the end user is the operator panel function. This is found  
in the Set-up Group of the menu. Operator Panel Function is an item in the Set-up Group. This item may  
be set to either Full Operation or Limited Operation.  
If the Operator Panel Function is set to Limited Operation the menu cannot be accessed and the  
operator panel switches listed below are not active.  
1. Print Quality  
2. Character Pitch  
The Operator Panel Function item is frequently set to Limited Operation on networks or other areas  
where many users share a printer. Limited Operation prevents the printer settings from being changed.  
This item cannot be changed through the OKISMART software. However, the print quality and character  
pitch may be set through your software application packages.  
Procedure  
To return the printer to Full Operation, you must modify the menu.  
CAUTION:  
Determine the preference of the end user regarding this feature. If the printer is on a network, do not  
reset this item without discussing the change with the network supervisor.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
To access the menu when the printer is set to Limited Operation, follow this procedure.  
1. Verify that continuous feed paper is installed.  
2. Verify that the ribbon is correctly installed.  
3. Verify that the width of the installed paper matches the paper width menu setting.  
CAUTION:  
If the Menu is set for wide paper, and narrow paper is used, the printhead will print on the platen. This  
could damage / destroy the printhead, platen, and ribbon.  
4. Power off the printer.  
5. Press and hold the SEL switch while powering on the printer.  
6. The MENU lamp will light. If the printer was selected, the SELECT lamp will light.  
When in Menu Mode, the functions printed below the operator panel switches are active.  
7. Press GROUP until Set-Up prints.  
8. Press ITEM until Operator Panel Function prints.  
9. Press SET until FULL OPERATION prints.  
10. Press EXIT to save the change and exit Menu Mode.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 104  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
Menu Settings  
Factory default settings are printed in Bold Italic.  
The tables show all possible menu settings available with the Microline 520/521.  
What you will actually see depends on the active emulation and the options installed.  
Group  
Item  
Setting  
Printer Control  
Font  
Emulation Mode  
Print Mode  
Pitch  
IBM PPR Epson FX ML  
Utility NLQ Courier NLQ Gothic HSD  
10 12 15 17.1 20 cpi  
No Yes  
Proportional Spacing  
Style  
Normal Italic  
Size  
Single Double  
Symbol Sets  
Character Set  
Language Set  
Set I Set II  
American French German British Danish I  
Swedish Italian Spanish I Japanese  
Norwegian Danish II Spanish II Latin  
American French Canadian Dutch Publisher  
Zero Character  
Code Page  
Slashed Unslashed  
USA Canada French Multilingual Portugal  
Norway  
Rear Feed  
Line Spacing  
6 8 LPI  
Form Tear-Off  
Off 500 ms 1 sec 2 sec  
No Yes  
Skip Over Perforation  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page Width *  
Page Length  
13.6" 8"  
11 11 2/3 12 14 17 3 3.5 4 5.5 6 7 8 8.5  
"
Gap Control  
Auto Gap Semi Auto Gap 1 2 3 4 5 6 7 8  
9
Bottom Feed  
Line Spacing  
6 8 LPI  
Form Tear-Off  
Skip Over Perforation  
Page Width *  
Off 500 ms 1 sec 2 sec  
No Yes  
13.6" 8"  
Page Length  
11 11 2/3 12 14 17 3 3.5 4 5.5 6 7 8 8.5  
"
Gap Control  
Auto Gap Semi Auto Gap 1 2 3 4 5 6 7 8  
9
Top Feed  
Line Spacing  
6 8 LPI  
Form Tear-Off * * * * * * *  
Bottom Margin  
Page Width *  
Off 500 ms 1 sec 2 sec  
Valid Invalid  
13.6" 8"  
Page Length  
11 11 2/3 12 14 17 3 3.5 4 5.5 6 7 8 8.5  
"
Gap Control  
Wait Time  
Auto Gap Semi Auto Gap 1 2 3 4 5 6 7 8  
9
1 sec 2 sec 500 ms  
Group  
Item  
Setting  
Set-Up  
Graphics  
Uni-directional bi-directional  
8 7  
7 or 8 Bit Graphics * *  
Receive Buffer Size  
64K, 1 line 32 K  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Paper Out Override  
Print Registration  
No Yes  
O 0.05 mm Left 0.10 mm Left 0.15 mm Left 0.20  
mm Left 0.25 mm Left 0.25 mm Right 0.20 mm  
Right 0.15 mm Right 0.10 mm Right 0.05 mm  
Right  
Operator Panel Function  
Reset Inhibit  
Full Operation Limited Operation  
No Yes  
Print Suppress Effective  
Auto LF  
Yes No  
No Yes  
Auto CR * * * *  
No Yes  
CSF Bin Select * * *  
Print DEL Code * *  
Bin 1 Bin 2  
No Yes  
SI Select Pitch (10 CPI) * *  
* *  
17.1 15 cpi  
SI Select Pitch (12 CPI) * *  
* *  
20 12 cpi  
Time Out Print  
Auto Select  
Valid Invalid  
No Yes  
Printhead Gap Adjust  
0 - 1 + 1  
* Model 521 only  
* * Appears only when Microline emulation is selected  
* * * Appears only when optional Cut Sheet Feeder is installed  
* * * * Appears only when IBM Proprinter emulation is selected  
* * * * * Appears only when Epson LQ emulation is selected  
* * * * * * Appears only when optional Serial Interface is installed  
* * * * * * * Appears only when optional Roll Paper Stand is installed  
Factory default settings are printed in Bold Italic.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
The tables show all possible menu settings available with the Microline 520/521.  
What you will actually see depends on the active emulation and the options installed.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 105  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.3.05 Top of Form  
General Information  
Top of Form is the distance from the top edge of the paper to the first print position on the page. The red  
line on the ribbon protector indicates the baseline of the Top of Form.  
Setting Top of Form  
1. Deselect the printer. The SEL lamp must not be lit.  
2. To set the TOF further down the page, press and hold the SHIFT switch while pressing the FF/LOAD  
switch. This will advance the paper in micro increments.  
3. To set the TOF higher on the page, press and hold the SHIFT switch while pressing the LF switch.  
This will retract the paper in micro increments.  
4. This setting will be kept in memory until you power off the printer or until you change the setting.  
5. To maintain this setting in the printers memory (even when the printer is powered off), press and hold  
the SHIFT switch while pressing the QUIET/TOF switch.  
6. Press the SEL switch.  
Reset the Top of Form to Factory Default  
1. Power off the printer.  
2. Press and hold the QUIET and FF/LOAD switches while you power on the printer.  
Note:  
The factory default Top of Form Setting is 1 inch.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 106  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.3.06 Paper Park  
General Information  
Paper Park allows the user to print using single (cut) sheet pages without removing continuous forms  
from the printer.  
Procedure: Continuous Feed to Single Sheet  
1. Remove any printed pages from the printer.  
2. Press PARK to retract the continuous forms paper from the paper path.  
3. Lift the paper separator to the upright position.  
4. Move the paper lever to the TOP (Single Sheet) position.  
5. Load the single sheet paper.  
Procedure: Single Sheet to Continuous Feed  
1. Remove any single sheet pages from the printer.  
2. Lower the paper separator to the Continuous Forms position (rear feed).  
3. Move the paper lever to the REAR or BOT position, as appropriate.  
4. Lower the paper support.  
5. Press FORM FEED to load the continuous forms paper into the printer.  
NOTE:  
When the printer is set to a different paper path, the printhead will travel back and forth. The pins are  
"gently" fired to sense paper thickness and set the printhead gap.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 107  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.3.07 Tear Feature  
NOTE:  
Tear is activated by pressing TEAR. It is a manual procedure.  
FORMS TEAR OFF is activated by changing a setting in the Menu. It is an automatic procedure.  
General Information  
This feature allows a printed page (rear or bottom feed, continuous form) to be torn off without wasting  
paper or adjusting the printer.  
Tear Feature advances the paper from the initial printing position to the tear off position. The top of the  
page (perforation) will be even with the tear bar. The tear bar is located under the clear top of the access  
cover.  
Paper will remain in the tear off position until the printer receives data. Then, the paper is retracted to the  
initial print position.  
To activate the Tear Feature, press TEAR.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 108  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.3.08 Forms Tear Off  
NOTE:  
Tear is activated by pressing TEAR. It is a manual procedure.  
FORMS TEAR OFF is activated by changing a setting in the Menu. It is an automatic procedure.  
General Information  
This feature allows a printed page (rear or bottom feed, continuous form) to be torn off without wasting  
paper or adjusting the printer.  
Forms Tear Off automatically advances the paper from the initial printing position to the tear off position.  
The top of the page (perforation) will be even with the tear bar. The tear bar is located under the clear  
top of the access cover.  
Paper will remain in the tear off position until the printer receives data. Then, the paper is retracted to the  
initial print position.  
When printing stops, the paper will advance to the tear off position.  
NOTE:  
If the software package being used "pauses" while sending data to the printer, Forms Tear Off may be  
activated (if it is enabled through the Menu). The pause must be for two or more seconds. No data is  
lost. Uneven print registration will occur due to the paper movement. If the problem occurs, deactivate  
Forms Tear Off through the Menu.  
DO NOT use Forms Tear Off with labels or multi-part forms.  
Remember to activate the Form Tear Off for the paper path you are using (rear feed or bottom feed).  
Vertical Line Spacing Problems  
NOTE:  
This information is also covered in Technical Service Bulletin 1704.  
Customers may experience problems with vertical line spacing when printing on continuous forms and  
using Forms Tear Off. The first page may not line up correctly. Following pages will not align. The  
customers may have worked with other Okidata printers and DID NOT experience the problem with the  
other printer(s). The difference is that the Microline 520 and Microline 521 printers DO NOT have a bail  
arm. The paper does not feed as "high" as it would in a printer with a bail arm.  
If you are experiencing problems with vertical line spacing when printing on continuous forms and using  
Forms Tear Off, perform the following steps to set the Top of Form position.  
1. Enter Menu Mode.  
2. Disable Form Tear Off.  
3. Exit Menu Mode.  
4. Deselect the printer.  
5. Use the Micro Feed buttons to set the Top of Form.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Press Micro Feed Up to advance the paper.  
Press Micro Feed Down to retract the paper.  
6. Enter Menu Mode.  
7. Enable Form Tear Off.  
8. Exit Menu Mode.  
Setting  
1. Verify that continuous feed paper is installed.  
2. Verify that the ribbon is correctly installed.  
3. Verify that the width of the installed paper matches the paper width menu setting.  
4. Power ON the printer.  
5. Press and hold the SHIFT switch while pressing the SEL switch to place the printer in Menu Mode.  
When in Menu Mode, the functions printed below the operator panels switches are active.  
6. Press GROUP until the desired Group prints (Rear Feed or Bottom Feed).  
7. Press ITEM until the desired Item prints (Form Tear Off)  
8. Press SET until the desired setting prints (Off, 500 mS, 1 sec, 2 sec).  
9. Press EXIT to save the change and exit Menu Mode.  
Using  
1. Load paper.  
2. Press FORM FEED  
3. The paper will advance past the start print position (Top of Form) to the tear bar position.  
4. The paper stays in this position until the printer receives data. Then, the paper will be retracted to the  
appropriate Top of Form position.  
5. A few seconds after printing stops, the paper advances to the tear bar position.  
Checking Top of Form with Form Tear Off Activated  
1. Load paper.  
2. Press and hold TEAR. When you release TEAR, the paper will return to the tear off position.  
3. The paper will retract to the Top of Form position.  
4. Release TEAR.  
5. The paper advances to the tear bar position.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 109  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.3.09 Resets  
Reset Menu to Factory Defaults  
CAUTION:  
Once the menu has been reset, all customized menu settings will be lost.  
Always print the menu before resetting the printer to factory defaults.  
To reset the menu to factory default settings, follow this procedure.  
1. Before resetting the Menu, Okidata STRONGLY RECOMMENDS printing the Menu.  
Printing the Menu provides a reference of customized settings.  
When the Menu is reset, all customized settings are LOST.  
2. Power off the printer.  
3. Press and hold SEL and LF while powering ON the printer.  
NOTE:  
Refer to the Printer Handbook for a list of the factory default settings.  
Reset the Top of Form to Factory Default  
1. Power off the printer.  
2. Press and hold the QUIET and FF/LOAD switches while you power on the printer.  
NOTE:  
The factory default Top of Form Setting is 1 inch.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 110  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.4 CLEANING  
3.4.01 General Information  
An accumulation of paper dust is the most frequent cause of print quality problems in a dot matrix printer.  
Small pieces of paper can cause paper jams. A dirty platen will smudge paper. It is important to clean the  
printer regularly, paying particular attention to the printhead area and the paper paths.  
If the lubrication procedures are not performed properly, the printer will require more frequent cleaning.  
Excessive lubricant attracts dust and accumulations build up quickly.  
Keeping the covers in place and performing the cleaning procedures correctly will help ensure the highest  
quality printer output.  
3.4.02 Cleaning Schedule  
Routine inspection and cleaning should be performed:  
1. every six months  
or  
2. every 300 hours of operating time.  
3.4.03 Cleaning Tools  
1. Clean, soft, lint-free cloth  
2. All-purpose cleaner  
3. Vacuum cleaner  
4. Platen cleaner  
3.4.04 Areas to be Cleaned  
Area  
Procedure  
3.2.25  
Cleaning Tool(s)  
Cloth and All-purpose cleaner  
Carriage Shaft  
Area around carriage shaft  
Space Rack  
3.2.25  
Vacuum, Cloth, and All-purpose cleaner  
Vacuum Paper Paths N/A Vacuum,  
3.2.13  
Cloth, and All-purpose cleaner  
Platen  
3.2.19  
3.2.06  
Cloth and Platen cleaner  
Covers  
Cloth and All-purpose cleaner  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 111  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.5 LUBRICATION  
3.5.01 General Information  
If the lubrication procedures are not performed properly, the printer will require more frequent cleaning.  
Excessive lubricant attracts dust and accumulations build up quickly. An accumulation of paper dust is the  
most frequent cause of print quality problems in a dot matrix printer.  
3.5.02 Lubrication Schedule  
Routine inspection and lubricating should be performed:  
1. once a year  
or  
2. every 600 hours of operating time.  
3.5.03 Lubrication Types  
1. Machine Oil or equivalent  
2. Moly-lube Grease or equivalent  
3.5.04 Lubrication Amounts  
Do NOT over-lubricate the printer. Operational problems are caused by excess lubricant. The excess  
lubricant causes dust to accumulate. These accumulations can jam gears or cause print problems.  
The Lubrication Table will direct you to use the following amounts of lubricant.  
1. Medium  
Oil: three to four drops  
Grease: thin coating (approximately .015 inch)  
2. Small  
Oil: one drop  
Grease: extremely thin coating (approximately .008 inch)  
3.5.05 Lubrication Table  
Download from Www.Somanuals.com. All Manuals Search And Download.  
3.5.06 Areas Not Lubricated  
Lubricant should never contact the parts listed below.  
1. Ribbon  
2. Platen Assembly (Rubber Face)  
3. Pressure Roller (Rubber Face)  
4. Tractor Pins  
5. Head Cable  
6. Space Motor Printed Circuit Board  
7. Electrical Contacts and Connections  
8. Space Rack  
CAUTION  
Do NOT lubricate the space rack. Lubricating the space rack will attract dust. If enough dust accumulates  
on the space rack, printing problems will occur.  
9. Teeth of the gears in the Gear Case Assembly  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 112  
Service Guide ML520/521  
Chapter 3 Maintenance & Disassembly  
3.6 SHIPPING INSTRUCTIONS  
3.6.01 Return for Service  
CAUTION:  
When shipping the printer, use the original packaging to prevent damage.  
Be sure to secure the printhead so it will not move during shipment.  
1. Locate the original packaging or order replacement packaging from Okidata. (Refer to Appendix B)  
2. Make sure the printhead is secured so it will not move during shipment.  
3. Remove the platen knob. Be sure to place it in the shipping container.  
4. Pack the unit, using the materials from Step 1.  
3.6.02 All Other Returns  
CAUTION:  
The product MUST be returned in the original packaging.  
The product MUST be returned with ALL originally supplied factory items.  
Be sure to secure the printhead so it will not move during shipment. 1. Locate the original packaging or  
order replacement packaging from Okidata. (Refer to Appendix B)  
2. Locate the originally supplied factory items. (Refer to Setting Up in the Printer Handbook)  
3. Make sure the printhead is secured so it will not move during shipment.  
4. Pack the unit, using the materials from Step 1.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 113  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.1.01 Introduction  
This section is used to isolate problems to the assembly level. Application problems and detection of  
faulty components on the printed circuit boards are NOT addressed.  
When troubleshooting a defective unit, follow these steps.  
1. Refer to Section 4.3, which explains where to check for updates to the troubleshooting information.  
2. Section 4.4 contains tips on preventing problems, as well as a list of common problems.  
3. Section 4.5 shows samples of abnormal outputs.  
4. Section 4.6 provides tables of error messages.  
5. Section 4.7 contains the Repair Analysis Procedures (RAPs). Each RAP will ask you questions or  
require you to make observations. The answers to these questions and the results of your  
observations determine your next course of action. Use the RAP Index to identify which RAP should  
be used to resolve the problem with the machine.  
6. Section 4.8 provides the procedures for various printer tests.  
7. Section 4.9 lists the resistance check points.  
8. Section 4.2 lists methods for reporting problems. If you encounter a situation that is NOT addressed  
by the documentation in this kit, please report the problem to Okidata, using one of the methods listed.  
Refer to the Service Center Reference Guide for information on contacting Okidata.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 114  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.1.02 Printer Serial Number Identification  
To identify the revision level of a printer, record the serial number from the back of the printer. Refer to the  
following to decode the serial number.  
Example  
Printer Serial Number: 401A0154693  
Date Code 401 (4 = year. 01 = month)  
Revision A  
Serial Number 0154693  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 115  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.1.03 Firmware Revision Identification  
To identify the revision level and part number of the firmware, print the Rolling ASCII Test or the Font  
Test.  
Refer to Section 4.8 of this Service Handbook for information on printing the tests.  
Header  
At the top of the test is a header.  
This header provides the following information: printer model (1), emulation (2), country (3), firmware  
revision level (4), firmware part number (5) and character generator revision number (6). This information  
is often required while performing service or when contacting Okidata. Have this information available  
during your service call.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 116  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.2 REPORTING PROBLEMS - General Information  
4.2.01 General Information  
Okidata strives to provide accurate and detailed service information through its training materials. The  
Technical Training Group realizes that service technicians have valuable experience, knowledge, and  
opinions. Okidata strongly encourages you to report any problems you may encounter when using the  
materials of this training kit. Please be as specific and detailed as possible. Your comments, suggestions,  
and criticisms are used to update and revise training kits.  
You should reference the training materials when servicing Okidata products. Most problems can be  
solved by using the information provided in the training materials. If you encounter a situation that cannot  
be solved, please let Okidata know.  
Refer to the Service Center Reference Guide for information on contacting Okidata.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 117  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.2.02 Problem Lists  
Technicians frequently request a list of common problems specific to a product. Technical Training Kits  
are written before a product is shipped to customers. Therefore, such information is NOT available when a  
product is first released.  
However, Okidata wants to respond to these requests. Okilink II provides round-table discussions on  
technical problems. Errors and corrections in the training materials are listed in the Training Section of  
Okilink II. The Technical Service Bulletins (also known as Okidata's Monthly Mail) are available via Okilink  
II. Situations that are NOT addressed in the reference documentation, technical service bulletins, or  
round-tables may be reported to the Dealer Service and Support Engineers (Contact Technical Support)  
or the Technical Training Group. You will receive a response to your message within one business day.  
The information on Okilink II is the most accurate and up-to-date technical information available from  
Okidata. This is only possible with your assistance. By reporting your suggestions, concerns, and  
problems, Okidata can provide the best possible information.  
Your cooperation is greatly appreciated. Thank you for your help!  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 118  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.2.03 Reporting Methods  
Okilink II  
You may use Okilink II to report your findings. Refer to the Service Center Reference Guide for  
information on using Okilink II.  
Course Critique  
Use the Course Critique to report any problems you find as you are completing the self-paced training.  
Fax Number  
If you wish to fax your response, please use the numbers listed in the Service Center Reference Guide.  
Mailing Address  
If you respond by mail, please use the appropriate address listed in the Service Center Reference Guide.  
Information Provided  
Please provide the following information when reporting problems.  
Okidata Dealer Number  
Technicians Name  
Company Name  
Company's Address (Street, City, State/Province, ZIP / Postal Code, Country)  
Telephone and Fax Numbers (with area / country access codes)  
Product Name  
Units Serial Number  
Firmware Revision Level  
Description of Problem  
Document Name (with page number or procedure) with error or problem.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 119  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.3 TROUBLESHOOTING UPDATES  
4.3.01 General Information  
Okidata distributes updated troubleshooting information in three ways.  
Okilink II  
Faxable Facts  
Technical Service Bulletins  
4.3.02 Okilink II  
Okilink II is Okidata's Bulletin Board Service. This service is available to all Okidata Certified Service  
Technicians. Okilink II provides troubleshooting and service information. Technicians can download files,  
ask questions of Okidata's technical support personnel, and participate in round table discussions about  
Okidata products and services. Technical Service Bulletins, Recommended Spare Parts Lists, Printer  
Drivers, Product Specifications, and Service Training Information are also available.  
Refer to the Service Center Reference Guide for information on accessing Okilink II.  
4.3.03 Faxable Facts  
Okidata's Faxable Facts is an automated fax document retrieval system. It is maintained by Okidata's  
Customer Information Center. Answers to common questions about Okidata products are available  
through Faxable Facts.  
Refer to the Service Center Reference Guide for information on accessing Faxable Facts.  
4.3.04 Technical Service Bulletins  
Okidata's Technical Service Bulletins (TSBs) contain technical information developed after product  
release. Firmware updates, part number changes, and procedural changes are some of the subjects  
covered by these bulletins. The TSBs are distributed through Okilink II.  
Refer to the Service Center Reference Guide for information on accessing Okilink II.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 120  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.4 TROUBLESHOOTING TIPS  
4.4.01 Preliminary Checks  
1. Is the product being operated under the proper ambient conditions?  
2. Does the paper being used meet the specifications for this product?  
3. Has the ribbon been replaced as recommended?  
4. Has the ribbon been installed properly?  
5. Is an Okidata ribbon being used?  
6. Is the printhead gap correctly set?  
7. Is the firmware the latest (current) revision?  
8. Are the printer drivers being used correct for the printer?  
9. Is the printer driver being used the latest (current) release?  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 121  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.4.02 Problem Categories  
There are three categories of problems that you might encounter when servicing the printer.  
ALARM Lamp Blinks (Fatal Errors)  
The following can cause the ALARM lamp to blink.  
Open Bail Arm  
Jammed Paper  
Printhead Cannot Move  
Other Fatal Error  
When the ALARM Lamp is blinking, check the items listed below.  
1. Close the bail arm.  
2. Check for a paper jam.  
3. Verify that the printhead moves freely.  
4. Record the status of the ALARM, PRINT QUALITY, and CHARACTER PITCH Lamps.  
5. Refer to the Alarm Lamp Codes Table. (Section 4.6)  
6. Locate the error.  
7. Perform the designated corrective action.  
Operational Errors  
An Operational Error is usually not accompanied by an ALARM Lamp.  
Refer to the Start Here Flowchart (Section 4.4.03) and perform the corrective action.  
ALARM Lamp Lights (Paper End/Jam Conditions)  
A solid ALARM Lamp usually indicates a cover open, paper jam or paper-end (out of paper) condition.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 122  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.4.03 START HERE Flowchart  
START  
Power ON the unit.  
Does the printer initialize?  
No Is the ALARM Lamp Blinking?  
No Refer to RAP 01.  
Yes Refer to Section 4.6 of the Service Handbook.  
Yes Load the printer with paper.  
Does the paper load without jamming?  
No Refer to RAP 04.  
Yes Perform the Rolling ASCII test. Refer to Section 3 of the Service Handbook.  
Is the output satisfactory?  
No Refer to RAP 06.  
Yes Are all operator panel switches operating properly?  
No Refer to RAP 09.  
Yes Has the problem been resolved?  
Yes End of procedure.  
No Does the parallel or serial interface port receive data from the host PC properly?  
Yes End of procedure.  
No Which port is not receiving data?  
Parallel Refer to RAP 10.  
Serial Refer to RAP 11.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 123  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.4.04 Tips for Preventing Image Problems  
1. Make sure that the ribbon is not "dried out". If the printer output is faded, install a new ribbon, then print  
another sample.  
2. Make sure that the paper you are using is within specifications. Paper specifications can be found in  
Section 1 of this Service Handbook.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 124  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.4.05 Common Problems  
1. Nothing happens when the unit is powered on.  
The unit may not be plugged in. Check the power cord connection to the outlet and to the printer. If a  
power strip is being used, make sure that it is powered ON. Check to be sure that an external fuse  
hasn't blown or that a circuit breaker hasn't tripped.  
2. The printer does not print when the computer sends data.  
The printer may be deselected. If the SEL light is out, press the SEL button to select the printer.  
The printer cable may not be securely connected. Check the cable to be sure that it is properly  
connected to both the PC and the printer.  
If you have installed the serial interface board, check to be sure that the board is firmly seated in the  
printer.  
3. A brand new ribbon has been installed and the printing is smeared and streaked.  
The plastic shield on the ribbon is either loose or missing. The shield must be left on the ribbon when  
you are installing the cartridge. To correct this situation, move the printhead to the center of the platen  
(careful - the printhead may be HOT!) and lift off the ribbon cartridge. Check the ribbon shield. If it is  
loose, secure it in place properly. If it is missing, locate it and install.  
4. Static electricity causes the paper to stick.  
In cold, dry weather, static charges can build up on continuous-form paper. This can make the paper  
cling to the paper separator. If you have this problem during high-volume printing jobs, try moving the  
single sheet paper guides on the separator together so that the paper rests on the guides rather than on  
the separator itself.  
5. The Print Quality and Character Pitch buttons on the front panel wont work.  
The Operator Panel Function Item on the printer MENU can be used to disable these buttons. If the  
printer is part of a customized system or if it is used by a number of people, the system manager may  
have used this option to make sure the printer is always set properly.  
NOTE:  
This feature also prevents access to the Menu. To access the Menu, power OFF the printer, then hold  
down the SEL key while powering ON.  
6. Strange symbols and incorrect fonts appear on the output when a document is printed.  
The printer driver that is engaged does not agree with the emulation selected for the printer.  
To check the emulation selected, first make sure that paper is loaded. Then, press the SEL and SHIFT  
buttons simultaneously to enter the Menu Mode. Next, press the GROUP button. This will print the  
emulation selected.  
If the emulation is not the one you want to use, press the SET button to change it to the one you want  
before exiting the Menu Mode. To exit, press the SEL and SHIFT buttons.  
If the emulation is correct, check your software documentation on how to select a printer driver. Then,  
check to be sure that you have selected one of the drivers listed for that emulation. Refer to the Printer  
Handbook for emulation/driver selections. The closer the driver is to the top of the list in the Printer  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Handbook, the more compatible it will be with your printer. If your software does not have any of the  
indicated drivers available, check with the software manufacturer to see if they have added any  
additional drivers since you purchased your software.  
If you have embedded any printer commands in your software, check to be sure that you have entered  
them correctly.  
7. Printing on the right side of the page is lighter or darker than the rest of the print on the page.  
Although the printer automatically sets the head gap, it sometimes may need a minor adjustment. To  
make this adjustment, enter the Menu Mode. Press SEL and SHIFT buttons simultaneously. To change  
the setting for the Printhead Gap Adjust under the Setup Group, use the following procedure.  
Press GROUP until Setup Group prints.  
Press ITEM until Printhead Gap prints.  
Press SEL to change the setting. The default setting is 0. If the printing is sometimes lighter, change the  
setting to - 1. If it is sometimes darker, change it to + 1.  
Press SEL and SHIFT buttons simultaneously to exit Menu Mode.  
8. There are vertical spacing problems when using continuous forms and Forms Tear Off.  
The printer does not have a bail arm, so pages do not feed as high as printers with bail arms. The first  
page does not line up correctly. Enter Menu Mode and disable Form Tear Off. Exit Menu Mode. Deselect  
the printer and set the paper position, using the Micro Feed buttons (hold SHIFT while pressing MICRO  
FEED UP or DOWN). Enter Menu Mode and enable Form Tear Off. Exit Menu Mode.  
9. The ALARM light is not on, but paper needs to be loaded.  
If the ALARM light is off, the printer "thinks" that paper is loaded. To correct this problem, press and  
release the SEL button. Then, hold the SHIFT button and press the RESET (Character Pitch) button.  
The ALARM light will come on and you will be able to load paper.  
10. The ALARM light is on and the Character Pitch 15 light is blinking.  
This indicates a paper loading error. To stop the blinking light, press the SEL button. Before trying to  
load paper, check to be sure that you have the paper lever in the correct position (BOT, TOP, REAR) for  
the path that you are using.  
CAUTION:  
Always power OFF the printer before you turn the platen knob.  
If the paper lever is in the correct position and you are using rear feed, lift up the paper separator and  
check to be sure that the paper is properly on the tractors and has not jammed.  
If the paper lever is in the correct position and you are using the optional bottom-feed push tractor, check  
the bottom tractor unit to be sure that the paper is properly installed on the tractors and that the paper  
has not jammed.  
Once the paper is correctly loaded, press and release the SEL button, then hold the SHIFT button and  
press the RESET (Character Pitch) button.  
11. Word processor files do not print the way the MENU and front panel are set.  
Before sending a file to the printer, many word processors send either an initialization string or an  
I-Prime signal to the printer.  
The initialization string contains codes that reset the printer to a default set of features. Otherwise, the  
printer might accidentally print using features set for a previous job. These codes will override the panel  
or MENU settings. To set your printer to ignore the reset codes, enter the printer MENU (hold down the  
SHIFT button while pressing SEL/MENU button) and change the Reset Inhibit item (in the Setup Group)  
to Yes. Please note that while this will stop the reset code from resetting your printer, but other codes in  
Download from Www.Somanuals.com. All Manuals Search And Download.  
the initialization string may still override the printer MENU and / or front panel settings.  
The I-Prime signal is sent over the parallel interface (pin 31) and will automatically override any settings  
you have made using the front panel buttons. To eliminate this problem, enter the Menu Mode (hold  
down the SHIFT button while pressing SEL/MENU button) and change the I-Prime item (in the Parallel  
I/F Group) to Invalid.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 125  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.5 ABNORMAL OUTPUT - Output Samples  
4.5.01 Output Samples  
Light Print on the Entire Page  
Possible Causes:  
1. Ribbon is "dried out". Replace the ribbon.  
2. Verify that the headgap menu setting is appropriate for the type of paper being used.  
3. Check / perform the printhead gap adjustment.  
4. Paper is not within specification. Refer to Section One for paper specification.  
Uneven Print Density  
Possible Causes:  
1. Printhead gap not within specification. Perform the printhead gap adjustment.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
2. Defective platen. Replace the platen.  
Smeared Print  
Possible Causes:  
1. Ribbon protector is missing or broken. Replace the ribbon protector.  
2. Verify that the headgap menu setting is appropriate for the type of paper being used.  
3. Check / perform the printhead gap adjustment.  
4. Paper is not within specification. Refer to Section One for paper specification.  
Inconsistent Line Feed  
Possible Causes:  
1. Power OFF the printer. Turn the platen knob. The platen should rotate smoothly. If it does not, remove  
the cause of the binding.  
2. Defective line feed motor. Replace the line feed motor.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Drifting Margin  
Possible Causes:  
1. Power OFF the printer. Move the carriage assembly. The carriage should move smoothly. If it does  
not, remove the cause of the binding.  
2. Refer to the next section and / or Technical Service Bulletin 3309.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 126  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
Left Margin Drifting Problem  
NOTE:  
This information is also provided in Technical Service Bulletin 1707.  
To correct a problem with the left margin drifting during print operations, follow this procedure.  
1. Manually slide the carriage assembly back and forth along the full length of the carriage shaft.  
Check for "drag" caused by the ribbon, a dirty space rack, or other obstructions.  
If you suspect that the ribbon is causing movement problems, check the movement of the carriage  
assembly with the ribbon removed OR with a new ribbon installed.  
2. Check the contact between the carriage frame and the space motor board assembly.  
Contact is made at the front edge of the board.  
Any gap will keep the space motor gear from fully engaging with the space rack. This will result in  
slippage problems, which will affect spacing operations.  
3. Check the printhead cable connections between the main control board and the space motor. Solid  
contact MUST BE made at all connections or print problems will occur.  
4. Check the condition of the printhead cable. If it is broken, torn, or sharply bent, replace the cable.  
5. If the problem continues, check the parts listed below (in the order given). Replace the suspected  
part. Be sure to test the printer after replacing each part.  
1. Carriage: Frame Set  
2. Motor: Space  
3. Rack: Space  
4. Cable: Printhead  
5. Board: Main Control  
6. If the problem continues, check all assemblies and connections. Then, contact Okidata Technical  
Information for further assistance.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 127  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.6 FAULT ALARMS  
4.6.01 General Information  
Follow these guidelines when using the Troubleshooting Tables.  
CAUTION:  
Always check that all connectors on the printer are making good contact.  
1. Record the status (OFF, solidly ON, Blinking) of the Operator Panel LEDs.  
2. Go to the Troubleshooting Table Index (Section 4.6.02).  
3. Look for the LED Indications you have observed.  
4. The Reference Number in the column at the right side of the Troubleshooting Table Index directs you  
to the appropriate item in the Troubleshooting Tables (Section 4.6.03).  
5. The Troubleshooting Tables will provide a Failure Description, Probable Cause and Recommended  
Action.  
6. The Recommended Action will direct you to the actions listed below.  
Follow a specific RAP.  
Replace items in a listed order.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 128  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.6.02 ALARM/LED Display Troubleshooting Table Index  
CAUTION:  
Always check that all connectors on the printer are making good contact.  
NOTE:  
Reference Numbers 25 and 26 use identical Operator Panel displays  
ALAR  
M
UTILITY  
PRO  
P
NLQ  
HSD  
On  
10  
12  
15  
17  
20  
SE  
L
MENU  
Referen  
ce  
Number  
Blinkin  
g
On  
On  
1
Blinkin  
g
On  
2
Blinkin  
g
On  
On  
On  
On  
On  
On  
On  
On  
On  
On  
On  
3
Blinkin  
g
On  
4
Blinkin  
g
On  
5
Blinkin  
g
On  
On  
6
Blinkin  
g
7
Blinkin  
g
On  
On  
On  
8
Blinkin  
g
On  
9
Blinkin  
g
10  
11  
Blinkin  
g
On  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Blinkin  
g
On  
12  
13  
14  
15  
16  
17  
18  
19  
20  
21  
22  
23  
Blinkin  
g
On  
On  
On  
Blinkin  
g
On  
Blinkin  
g
On  
On  
On  
Blinkin  
g
On  
Blinkin  
g
On  
Blinkin  
g
On  
On  
On  
On  
On  
Blinkin  
g
On  
Blinkin  
g
On  
Blinkin  
g
On  
On  
On  
On  
On  
On  
On  
On  
Blin  
kin  
g
On  
Blin  
kin  
g
On  
24  
On  
On  
On  
On  
On  
On  
Blinkin  
g
25  
26  
Blinkin  
g
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 129  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.6.03 ALARM/LED Display Troubleshooting Tables  
CAUTION:  
Always check that all connectors on the printer are making good contact.  
Reference  
Number  
Failure Description  
Cause  
Recommended Action  
Refer to RAP 02.  
1
Space Motor Alarm  
Space motor IPT does  
not occur in specified  
time.  
2
3
Printhead Detection  
Alarm  
Printhead does not  
home.  
Refer to RAP 03.  
Printhead A/D Alarm  
Thermistor is open or +5  
vdc shorted.  
Check the printhead  
connection. Then  
replace the main control  
board the carriage cable  
and the printhead.  
4
5
Printhead Gap Alarm Self adjustment was not  
successful.  
Check the printhead  
connection. Then  
replace the main control  
board the carriage cable  
and the printhead.  
Printhead Data  
Transfer Alarm  
Printhead parity  
error<R>was not  
Replace the main control  
board the carriage cable  
and the printhead.  
recovered or print head  
was not seated properly.  
6
7
Printhead Type  
Alarm  
24 pin printhead is  
connected in a 9 pin  
printer.  
Replace the printhead  
with a 9 pin printhead.  
Printhead  
Connection Alarm  
(1)  
Overdrive signal is  
active but no current is  
detected.  
Check the printhead  
connection. Then  
replace the main control  
board the carriage cable  
and the printhead.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
8
9
Printhead  
Connection Alarm  
(2)  
Self adjust was not  
successful. Head gap is connection. Then  
too small or too narrow.  
Check the printhead  
replace the main control  
board the carriage cable  
and the printhead.  
Line Feed / Space  
Motor Driver Alarm  
High driver temperature.  
The TSD signal has not  
changed.  
Replace the following:  
main control board line  
feed motor and space  
motor.  
10  
11  
12  
13  
MPU Internal RAM  
Alarm  
Read/write error  
Check sum error  
Read/write error  
Check sum error  
Replace the main control  
board.  
Program ROM  
Alarm  
Replace the main control  
board and/or ROM.  
RAM on Main  
Control Board  
Replace the main control  
board.  
CG ROM Alarm  
Replace the main control  
board.  
CAUTION:  
Always check that all connectors on the printer are making good contact.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 130  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.7 REPAIR ANALYSIS PROCEDURES (RAPs)  
4.7.01 Using the RAPs  
When using the Repair Analysis Procedures, follow these steps.  
1. Go to the RAP Index.  
2. Find the RAP which is associated with the printers problem.  
3. Go to the appropriate RAP.  
4. All RAPs begin with a START statement, followed by questions or another type of statement.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 131  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.7.02 RAP Index  
RAP  
1
Number Description  
No Power Supplied to Printer  
No Spacing Operation  
2
3
Printhead Homing Error  
Paper Jam During Paper Loading  
Printhead Not Firing Pins  
Poor Print Quality  
4
5
6
7
Ribbon Feed Problem  
8
Line Feed Problem  
9
Operator Panel Malfunction  
Parallel Interface Problem  
Serial Interface Problem  
10  
11  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 132  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
RAP 01 No Power Supplied to Printer  
START  
The printer does not power On when the AC switch is turned ON.  
Check the AC cable.  
Is it correctly connected?  
Yes Check the fuse on the power supply board and F1 of the main control board. Are they open?  
No Go to A.  
Yes Replace the fuse(s) with fuse(s) of the same rating.  
Is the problem resolved?  
Yes End of procedure.  
No Go to A.  
B
No Remove the cable from CN3 on the main control board.  
Refer to Appendix A of this Service Handbook for voltage check points on CN3 of the main control  
board. Check the output voltages of the secondary of the transformer.  
Replace the following in the order listed below. Check operation before replacing next item in list.  
1. Operation Panel.  
2. Power Transformer.  
Has the problem been resolved?  
Yes End of procedure.  
No Contact Technical Support.  
A
Remove the cable from CN7 of the main control board. Then, power ON the unit.  
Do the operation panel LEDs light?  
No Go to B.  
Yes Power OFF the unit. Remove the printhead. Power ON the unit.  
Has the problem been resolved?  
Yes Replace the printhead.  
Has the problem been resolved?  
Yes End of procedure.  
No Go to B.  
No Replace the following in the order listed below. Check operation before replacing next item in list.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
1. Ribbon Feed Mechanism.  
2. Carriage Cable.  
3. Main Control Board  
4. PROM 05CA  
Has the problem been resolved?  
Yes End of procedure.  
No Contact Technical Support.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 133  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
RAP 02 No Spacing Operation  
START  
The alarm LED blinks.  
Is the carriage assembly binding or jammed?  
No Make sure the carriage cable is properly connected to the space motor assembly and CN7 on the  
main control board.  
Go to A.  
Yes 1. Remove the ribbon to verify that the ribbon is not jammed.  
2. Remove the space motor assembly  
3. Inspect the teeth on the space rack and the space motor gear.  
4. Go to A.  
A
Has the problem been resolved?  
Yes End of procedure.  
No Is the fuse F2 on the main control board open?  
No Go to B.  
Yes Replace the main control board.  
Has the problem been resolved?  
Yes End of procedure.  
No Go to B.  
B
Verify that +40 volts is present on CN7 main control board (Refer to Appendix A of the Service  
Handbook).  
Has the problem been resolved?  
Yes End of procedure.  
No Replace the carriage cable.  
Has the problem been resolved?  
Yes End of procedure.  
No Replace the ribbon feed mechanism  
Has the problem been resolved?  
Yes End of procedure.  
No Replace the PROM (O5CA)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Has the problem been resolved?  
Yes End of procedure.  
No Contact Technical Support.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 134  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
RAP 03 Printhead Homing Error  
START  
Printhead does not return to the home position.  
Make sure the carriage cable is properly connected to the space motor assembly and CN8 on the main  
control board.  
Make sure the power connector cable is properly connected to CN3 on the main control board.  
Does the space motor assembly move manually?  
No Remove the space motor assembly and inspect the space motor and space rack for dirt and worn  
teeth.  
Go to A  
Yes Are there any breaks in the carriage cable?  
Yes Replace the carriage cable assembly.  
Go to A  
No Verify that ribbon feed mechanism is properly fastened to the space motor assembly.  
Go to A  
A
Does the carriage move slightly to the left after turning the power on?  
No Replace the space motor assembly.  
Has the problem been resolved?  
Yes End of procedure.  
No Contact Technical Support.  
Yes Replace the ribbon feed assembly.  
Has the problem been resolved?  
Yes End of procedure.  
No Replace the main control board.  
Has the problem been resolved?  
Yes End of procedure.  
No Replace the space motor assembly.  
Has the problem been resolved?  
Yes End of procedure.  
No Contact Technical Support.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 135  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
RAP 04 Paper Jam During Paper Loading  
START  
Check paper path release lever for proper position. Make sure the paper path is clear.  
Which of the following paper jams have occurred?  
1. Paper bent at top left corner.  
Check the support protector to see if it covers the left side of the paper properly.  
Go to A.  
2. Paper has torn ends.  
Check the ribbon protector.  
Check the pull up roller cover to see that it is closed properly.  
Go to A.  
3. Paper squeezed from either end.  
Check around the pressure roller mechanism.  
Check the front pressure springs to see that they are mounted properly. There are three springs in the  
Microline 520 and five springs in the Microline 521.  
Check the tension of all the front pressure rollers to see if they are the same. Top springs: 250 g. Rear  
Springs: 90 g.  
Make sure that the front release gear arm and the gear of the front release gear shaft are in the proper  
position.  
Go to A.  
A
Has the problem been resolved?  
Yes End of procedure.  
No Check that the head gap is set properly.  
Has the problem been resolved?  
Yes End of procedure.  
No Contact Technical Support.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 136  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
RAP 05 Printhead Pins Not Firing  
START  
Missing dots on output.  
Verify that the printhead gap is set correctly.  
Ensure the carriage cable is making firm contact with CN7 on the main control board and the space motor  
assembly. Inspect both ends of the carriage cable for worn edges.  
Has the problem been resolved?  
Yes End of procedure.  
No Replace the printhead.  
Has the problem been resolved?  
Yes End of procedure.  
No Replace the main control board  
Has the problem been resolved?  
Yes End of procedure.  
No Replace the carriage cable.  
Has the problem been resolved?  
Yes End of procedure.  
No Replace the space motor assembly.  
Has the problem been resolved?  
Yes End of procedure.  
No Contact Technical Support.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 137  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
RAP 06 Poor Print Quality  
START  
Is the print head gap properly set?  
Yes Go to A  
No Go to B  
A Replace the printhead  
Has the problem been resolved?  
Yes End of procedure.  
No Go to C.  
C Replace the main control board.  
Has the problem been resolved?  
Yes End of procedure.  
No Check that the carriage cable is making good contact with the main control board and the carriage  
assembly. Replace the cable if it is worn or bent.  
Has the problem been resolved?  
Yes End of procedure.  
No Contact Technical Support.  
B Adjust the print head gap (Refer to Section 3 of this Service Handbook).  
Has the problem been resolved?  
Yes End of procedure.  
No Power ON the unit and view the head gap indicator.  
Does the head gap indicator display a range of 9?  
Yes Go to A  
No Replace the ribbon feed mechanism.  
Has the problem been resolved?  
Yes End of procedure.  
No Go to C  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 138  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
RAP 07 Ribbon Feed Problem  
START  
The ribbon feed does not function properly.  
Verify that both ends of the carriage cable are connected correctly.  
Make sure the ribbon shield is fastened properly.  
Remove the ribbon cartridge.  
Grasp the carriage. Manually move the carriage left and right.  
Does the ribbon drive shaft rotate?  
Yes Change the ribbon cartridge.  
End of procedure.  
No Remove the ribbon feed mechanism.  
Manually move the carriage left and right.  
Does the space motor shaft rotate freely?  
Yes Replace the ribbon feed mechanism.  
End of procedure.  
No Replace the space motor assembly.  
Has the problem been resolved?  
Yes End of procedure.  
No Replace the main control board.  
Has the problem been resolved?  
Yes End of procedure.  
No Contact Technical Support.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 139  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
RAP 08 Line Feed Problem  
START  
No line feed operation.  
Make sure that the line feed cable is properly connected to the line feed motor and CN5 of the main  
control board.  
Power OFF the printer. Manually rotate the platen.  
Does the platen rotate smoothly?  
Yes Go to A  
No Is the left platen gear broken?  
Yes Replace the platen assembly.  
End of procedure.  
No Is the line feed idle gear broken?  
Yes Replace the line feed motor assembly or the line feed idle gear.  
End of procedure.  
No Are the right platen gear, idle gear and/or change gear broken?  
Yes Replace the respective assembly.  
End of procedure.  
No Set the change lever to the rear position.  
Does the platen rotate smoothly?  
Yes Replace the tractor feed assembly.  
End of procedure.  
No Check the gears on the tractor feed assembly and platen assembly for broken or missing teeth.  
Replace the defective assembly.  
Go to A  
A
Replace the line feed motor assembly.  
Has the problem been resolved?  
Yes End of procedure.  
No Replace the main control board.  
Has the problem been resolved?  
Yes End of procedure.  
No Contact Technical Support.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 140  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
RAP 09 Operation Panel Malfunction  
START  
The operation panel does not function properly.  
Do the operation panel LEDs light when power is applied?  
Yes Make sure the cable from CN1 of the operation panel is properly connected to CN7 on the main  
control board.  
Go to A  
No Check the F1 fuse on the main control board and the fuse on the power supply board. Are they open?  
Yes Replace the open fuse with one that has the proper rating.  
Go to A  
No Replace the power supply unit.  
Go to A  
A
Has the problem been resolved?  
Yes End of procedure.  
No Replace the operation panel board.  
Has the problem been resolved?  
Yes End of procedure.  
No Replace the main control board.  
Has the problem been resolved?  
Yes End of procedure.  
No Contact Technical Support.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 141  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
RAP 10 Parallel Interface Problem  
START  
No parallel port communication.  
Is the SEL LED blinking?  
Yes The printer is in the Print Suppress mode.  
Disable the menu item Print Suppress if the function is not required.  
End of procedure.  
No Does the SEL LED light ?  
Yes Go to A  
No Press SEL key.  
Has the problem been resolved?  
No Disconnect the cable.  
Does the SEL LED light ?  
Yes Change the menu item I-prime to invalid.  
No Go to A  
Yes Is data being received properly?  
Yes End of procedure.  
No Check that the cable is properly connected to the Host PC and the correct LPT port is selected.  
Does the SEL LED light?  
No Go to A  
Yes Change the menu item I-prime to invalid.  
End of procedure.  
A
Replace the interface cable.  
Has the problem been resolved?  
Yes End of procedure.  
No Replace the main control board.  
Has the problem been resolved?  
Yes End of procedure.  
No Contact Technical Support.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 142  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
RAP 11 Serial Interface Problem  
START.  
Are you using a cable with the proper number of pins?  
No Change the interface cable.  
Has the problem been resolved?  
Yes End of procedure  
No Go to A  
Yes Is the ALARM LED blinking?  
Yes Refer to Section 4.6 of the Service Handbook.  
Has the problem been resolved?  
Yes End of procedure  
No Go to A  
No Go to A  
A
Check the serial interface parameters for the RS232C (in the Printer Menu): baud rate, word length, parity,  
protocol, busy signal and parity.  
Has the problem been resolved?  
Yes End of procedure  
No Go to B  
B
Check the voltages on the main control board.  
Is 10 VAC being supplied to the main control board?  
Yes Replace the RS232C board.  
Has the problem been resolved?  
Yes End of procedure.  
No Replace the main control board.  
Has the problem been resolved?  
Yes End of procedure.  
No Contact Technical Support.  
No Replace the power supply unit.  
Has the problem been resolved?  
Yes End of procedure.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
No Replace the RS232C board.  
Are + 8 vdc / - 8 vdc present on the main control board? (Refer to Appendix A of this Service  
Handbook).  
Yes Replace the RS232C board.  
Has the problem been resolved?  
Yes End of procedure.  
No Contact Technical Support.  
No Replace the main control board.  
Has the problem been resolved?  
Yes End of procedure.  
No Contact Technical Support.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 143  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.8 PRINTER TESTS  
4.8.01 General Information  
This section covers the tests listed below.  
Rolling ASCII Test  
Font Test  
Serial Interface Loopback Test  
Hexadecimal Dump Mode  
The Rolling ASCII and Font Tests check print operations.  
The Serial Interface Loopback Test checks the operation of the serial interface board.  
The Hexadecimal Dump Mode checks the data transfer between the computer and printer.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 144  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.8.02 Rolling ASCII Test  
General Information  
The rolling ASCII test is a continuous printout of all 96 ASCII characters.  
Use this test to check the following items.  
1. Print Quality  
Across the entire length of a line  
Down the entire page  
2. Line Spacing  
3. Left Margin Alignment  
At the top of the test is the printer type (1), emulation (2), country (3), and firmware revision level (4). This  
information is often required while performing service or when contacting Okidata. Have this test available  
during your service call.  
CAUTION  
Before running this test, make sure that continuous feed paper is loaded.  
If you are running this test on a Microline 521, use wide paper or have the page width set for 8.5" x 11" in  
the printer menu.  
Running the test without paper loaded or having the wrong width paper loaded will allow the printhead to  
print on the platen. This will dirty the platen, cause excessive wear on the ribbon, and may damage the  
platen, ribbon, and printhead.  
Procedure  
Follow these steps to print the Rolling ASCII Test.  
1. Load the correct size continuous feed paper.  
2. Power off the printer.  
3. Press and hold the QUIET switch while powering on the printer. You must hold the QUIET switch until  
the test starts to print.  
4. The test will continue to print until you press the SEL switch or run out of paper.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 145  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.8.03 Font Test  
General Information  
The font test is a one page sample printout of each available typeface.  
HSD 10 cpi  
HSD 12 cpi  
HSD 17.1 cpi  
Utility 10 cpi  
Utility 12 cpi  
Utility 17.1 cpi  
NLQ 10 cpi  
NLQ 12 cpi  
NLQ 10 cpi Double Height / Double Width  
At the top of the test is the printer type (1), emulation (2), country (3), and firmware revision level (4).  
This information is often required while performing service or when contacting Okidata. Have this test  
available during your service call.  
CAUTION  
Running the test without paper loaded will allow the printhead to print on the platen. This will dirty the  
platen, cause excessive wear of the ribbon, and may damage the platen, ribbon, and printhead.  
Procedure  
Follow these steps to print the font test.  
1. Load the paper.  
2. Power off the printer.  
3. Press and hold the LF switch while powering on the printer. You must hold the LF switch until the test  
starts to print.  
4. The one page test will print, then stop.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 146  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.8.04 Serial Interface Loopback Test  
NOTE:  
In order to run this test, the serial interface board must be installed with a serial loopback test connector  
attached to it.  
To perform the serial interface loopback test, follow these steps.  
1. Place the printer in the Serial Diagnostic mode.  
Set the Diagnostic Test menu item to YES.  
2. Power off the printer.  
3. Attach the loopback connector to the serial port.  
4. Install continuous feed paper.  
5. Power on the printer.  
6. The message LOOP TEST prints.  
7. The size of the Message Buffer prints.  
8. One of the following three messages prints next.  
If the message OK prints, the message buffer has been tested and no problems were found.  
If the message BAD prints, there is a problem with the message buffer.  
If the message IF BAD prints, the signal logic was tested and a problem was found.  
9. Hexadecimal characters 20 through 7F are transmitted through the transmit data line.  
10. The receive data line receives the characters.  
11. The message buffer stores the characters.  
12. The data prints.  
13. The test runs until the printer is powered off or the SELECT switch is pressed.  
Loopback Connector Configuration  
1. Jumper the following pins together.  
Pin 2 to Pin 3  
Pin 4 to Pin 5  
Pin 8 to Pin 11  
Pin 6 to Pin 20  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 147  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
Serial Cable Information  
The information in this section will help you make a serial cable to connect between the printer and  
computer.  
Refer to the computer documentation to determine the cable requirements on the computers end.  
The printer has the following cable requirements.  
Shielded, RS-232C cable  
UL and CSA approved  
No more than 50 feet long  
Cannon DB-25P plug (or equivalent) with 25 pins  
Cannon DB-C2-J9 (or equivalent) connector shell  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 148  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
Serial Interface Signal Requirements  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 149  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
Commonly Used Serial Cable Configurations  
IBM 25-Pin Cable Configuration  
Computer Printer  
IBM 9-Pin Cable Configuration  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 150  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.8.05 Hexadecimal Dump Mode  
General Information  
The hexadecimal dump mode allows you to view the data sent from a computer to the printer. When the  
printer is in hex dump mode, all data received (both printable characters and control codes) will be printed  
in both hexadecimal and ASCII format.  
NOTE:  
In the ASCII format, all non-printable characters will be represented by a period.  
Example  
Below is a line of BASIC code.  
LPRINT CHR$(27) ;"0";CHR$(30);"This is an example of hexadecimal dump."  
Below is the same line as it would appear in Hexadecimal Dump Mode.  
This is an example of hexadecimal dump:  
1B 30 1E 54 68 69 73 20 69 73 20 61 6E 20 65 78 .0.  
61 6D 70 6C 65 20 66 20 61 20 68 65 78 61 64  
65 63 69 6D 61 6C 20 64 75 6D 70 2E 0D 0A  
Procedure  
Follow these steps to engage the Hexadecimal Dump Mode.  
1. Make sure the printer is connected to a computer.  
2. Verify that paper is loaded.  
3. Verify that the ribbon and printhead are correctly installed.  
4. Power OFF the printer.  
5. Press and hold the SEL and FF/LOAD switches while powering on the printer.  
6. Hold the switches until the printer prints the line:  
Hex Data Dump  
7. The printer is ready to receive data in the Hexadecimal Dump Mode.  
8. Send data to the printer from the computer.  
9. To exit Hexadecimal Dump Mode, power OFF the printer.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 151  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.9 RESISTANCE CHECKS  
4.9.01 General Description  
The charts on the following pages provide information needed to determine if the printhead and motors  
used in the printer are defective.  
NOTE:  
The printhead coil resistance values ARE NOT LISTED.  
The individual printwire control lines CANNOT be accessed on this printhead.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 152  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
Layout Diagram  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 153  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.9.02 Printhead  
Interconnect Diagram: Control Board to Printhead  
NOTE:  
The printhead coil resistance values ARE NOT LISTED.  
The individual printwire control lines CANNOT be accessed on this printhead.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 154  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.9.03 Line Feed Motor Resistance  
The resistance of each coil should be approximately 13 ohms.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 155  
Service Guide ML520/521  
Chapter 4 Failure & Repair Analysis  
4.9.04 Space Motor Resistance  
The resistance of each coil should be approximately 5 ohms.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 156  
Service Guide ML520/521  
Chapter A Reference Charts  
A.1 OVERVIEW - A.1.01 General Information  
This section describes the characteristics of the printed circuit boards used in the unit.  
The following areas are covered.  
Function  
Firmware  
Fuses  
Jumpers  
Sensors  
Switches  
Test Points  
Where an item is not applicable, the word NONE will be listed.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 157  
Service Guide ML520/521  
Chapter A Reference Charts  
A.2 INDEX TO CHARTS  
Description  
Board Designation  
Section  
Main Controller Board  
Operator Panel Board  
Power Supply Assembly  
Space Motor Board  
FJIM  
A.2.01  
LEOP  
N/A  
A.2.02  
A.2.03  
A.2.04  
A.2.05  
N/A  
RS232-C Serial Interface Board  
LXHI  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 158  
Service Guide ML520/521  
Chapter A Reference Charts  
Board Layout  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 159  
Service Guide ML520/521  
Chapter A Reference Charts  
A.2.01 Main Controller Board (FJIM)  
Function  
The main controller board contains a microprocessor, EPROM, EEPROM, drive circuitry, 128 Kbyte  
DRAM, sensors and interface connector. The AC voltages from the power supply are rectified and  
regulated on the main controller board.  
Firmware  
05CB: CMOS Dynamic RAM (1 MBit)  
05CA: EPROM (Program)  
Fuses  
F1: 125 Volt 2 amp. (AC line fuse)  
F2: soldered - 2 amp. (protects the +40vdc motor drive circuit)  
Jumpers  
NONE  
Sensors  
SNS1: Rear / Top Feed Paper Out Sensor  
SNS2: Bottom Feed Paper Out Sensor  
Switches  
BASW: Paper Path Select Switch  
Test Points  
Frame Ground CN1 pins 37,38  
Logic Ground CN1 pin 33  
+5 vdc : CN7 - Pin 6 (logic circuitry voltage)  
+40 vdc: CN7 - Pins 29 and 31 (Printhead, Space Motor / Line Feed Motor Drive Voltage)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 160  
Service Guide ML520/521  
Chapter A Reference Charts  
A.2.02 Operator Panel Board (LEOP)  
Function  
The operator panel control LSI send commands to the microprocessors serial I/O port whenever the  
operator panels switches are pressed. The operator panel LED display provides information on fault  
alarms and printer status.  
Firmware  
NONE  
Fuses  
NONE  
Jumpers  
NONE  
Sensors  
NONE  
Switches  
SEL (Select)  
SHIFT  
LF (Line Feed)  
FF (Form Feed)  
TEAR  
PARK  
QUIET  
PQ (Print Quality)  
CP (Character Pitch)  
Test Points  
NONE  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 161  
Service Guide ML520/521  
Chapter A Reference Charts  
A.2.03 Power Supply Assembly  
Function  
The power supply board is comprised of a noise filter board and transformer. The power supply board  
provides AC voltages to the main controller board via CN-3.  
Firmware  
NONE  
Fuses  
F1: 125/250V 2.5 amp. AC line fuse  
Jumpers  
NONE  
Sensors  
NONE  
Switches  
SW: Power Switch  
Test Points  
Transformer secondary voltages  
CN 3 pin 1: 17.5 VAC  
CN 3 pin 2: 0 VAC  
CN 3 pin 3: 6.6 VAC  
CN 3 pin 4: 0 VAC  
CN 3 pin 5: 0 VAC  
CN 3 pin 6: 6.6 VAC  
CN 3 pin 7: 0 VAC  
CN 3 pin 8 : 18.5 VAC  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 162  
Service Guide ML520/521  
Chapter A Reference Charts  
A.2.04 Space Motor Board  
Function  
The space motor board contains an encoder disk and photosensor. The encoder disk and the  
photosensor generate phase signals. These signals governs the speed and direction of the space motor  
via the LSI and microprocessor.  
Firmware  
NONE  
Fuses  
NONE  
Jumpers  
NONE  
Sensors  
Photosensor: used to monitor space motor movement.  
Switches  
NONE  
Test Points  
NONE  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 163  
Service Guide ML520/521  
Chapter A Reference Charts  
A.2.05 RS232-C Serial Interface Board - Option (LXHI)  
Function  
This board provides you serial interface capabilities. The serial interface parameters can be set through  
the printer menu.  
Firmware  
Masked to the MPU: Socket is empty  
Fuses  
NONE  
Jumpers  
SP1: EPROM Address Select Jumper (position as shown) EPROM is masked to MPU  
Sensors  
NONE  
Switches  
NONE  
Test Points  
NONE  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 164  
Service Guide ML520/521  
Chapter B Illustrated Parts Listing  
B.1 OVERVIEW - B.1.01 General Information  
This appendix will assist you in identifying the assemblies and parts of the product.  
Use Section Four (Failure Analysis) to determine the defective part(s).  
Locate the part and its part number in this section.  
Appendix B is cross-referenced to Section Three (Maintenance).  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 165  
Service Guide ML520/521  
Chapter B Illustrated Parts Listing  
Format  
The format for this appendix is a series of tables with diagrams. The tables contain the item reference  
number, the Okidata and Oki-Japan (Oki-J) part numbers, the part description, a comments section, and  
the disassembly procedure.  
Items with the comments RSPL (Recommended Spare Parts List), Consumable, Document, or Option are  
available from Okidata. Items without these comments are usually not stocked.  
Some items are only available as assemblies. Every effort has been made to clearly indicate which items  
are in assemblies and which are not.  
N/A will appear where a part number is not available.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 166  
Service Guide ML520/521  
Chapter B Illustrated Parts Listing  
Current Part Numbers  
Okidata has made every effort to include current part numbers in this Service Handbook at the time of  
publishing.  
However, technical information frequently changes. These changes often include new or modified parts,  
with new or modified part numbers.  
Please refer to the following resources for current part numbers and pricing.  
Okidata's Electronic Bulletin Board (Okilink II) contains current part numbers, prices, and  
recommended stocking levels for each item listed as a recommended spare part. For instructions on  
accessing Okilink II, refer to the Service Center Reference Guide.  
Okidata's Faxable Facts is an automated fax document retrieval system. Part numbers and pricing are  
available through Faxable Facts. For instructions on accessing Faxable Facts, refer to the Service  
Center Reference Guide.  
Okidata's Technical Information Group is a telephone support line reserved for Authorized Dealers.  
Part numbers and pricing are available through Technical Information. For instructions on accessing  
Technical Information, refer to the Service Center Reference Guide.  
REMEMBER  
Current part numbers, recommended stocking levels, and pricing information are available through Okilink  
II, Faxable Facts, and Technical Information. Refer to the Service Center Reference Guide for information  
on accessing these resources.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 167  
Service Guide ML520/521  
Chapter B Illustrated Parts Listing  
B.1.02 Definition of Terms  
Assemblies  
Assemblies are parts grouped under a single description and/or part number. Generally, individual items in  
an assembly are not available from Okidata.  
Assemblies are surrounded by broken line boxes in the diagrams.  
Assemblies will say "Includes xx xx" under the Comments section of the tables.  
Parts in assemblies will say "Part of xx" under the Comments section of the tables.  
Blank  
Okidata does not recommend stocking this item. This item should be purchased on an As Required  
Basis only.  
The availability of this item is NOT guaranteed by Okidata.  
Consumable  
A consumable is a supply item which has a specified life and must be periodically replaced. It is  
purchased and installed by the end user. Okidata machines are designed to work exclusively with Okidata  
consumables. By using genuine Okidata consumable products, the investment made in the equipment is  
protected.  
Document  
A document is a printed item which supports the service and marketing of a product. Various documents  
are available from Okidata.  
Drivers  
Printer drivers are updated frequently. Please refer to Okilink II for the latest printer driver information.  
Firmware  
Firmware is revised frequently. Please refer to Okilink II for the latest firmware information.  
Option  
An option is a part/assembly which is added to a product. The option expands the products functionality.  
An option may or may not be installed by the end user. Instructions for installation accompany each  
option.  
Option RSPL  
Okidata recommends that this part/assembly be on hand for servicing installed options.  
RSPL  
Okidata recommends that this part/assembly be on hand for servicing.  
Technical Service Bulletins  
Technical Service Bulletins (TSBs) are also referred to as Okidata's monthly mail.  
The TSBs contain the latest information on firmware revisions, procedure changes, and technical  
Download from Www.Somanuals.com. All Manuals Search And Download.  
information updates.  
Okidata distributes the TSBs through Okilink II. The TSBs are issued monthly.  
520  
This part is specific to the Microline 520 printer.  
521  
This part is specific to the Microline 521 printer.  
Both  
This part is used by both the Microline 520 and Microline 521 printers.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 168  
Service Guide ML520/521  
Chapter B Illustrated Parts Listing  
B.1.03 Parts Ordering Information  
Service Center Reference Guide  
When a technician has successfully completed a Service Training Course for a product and the Dealer  
has become Service Authorized, an information package is provided to the Dealer. The Okidata Service  
Center Reference Guide outlines the following items.  
Responsibilities of Okidata Service Centers  
Spare parts and consumables information  
Procedures for warranty repairs  
Product Training, Certification, and Authorization  
Product Support information  
Okidata Depot information and services  
Third Party Service information  
Information about Okidata's Customer Information Center  
Okidata Service and Support telephone numbers.  
The Service Center Reference Guide contains the procedures to follow for ordering parts. Please read,  
understand, and follow these procedures. Service Authorization for a specific product must be obtained  
before a Dealer can submit warranty claims.  
Direct questions regarding the Service Center Reference Guide to Okidata Dealer Service. Refer to the  
Service Center Reference Guide for information on contacting Okidata.  
Placing a Parts Order  
All authorized Okidata resellers may order spare parts and consumables for Okidata products. Orders are  
placed through Okidata's Logistics Department.  
Please refer to your Service Center Reference Guide for details on ordering parts.  
You should have the following information available before you place your order.  
Okidata Dealer Authorization Number  
Okidata Customer Number  
Your Purchase Order Number  
Okidata Part Number(s)  
Use this Appendix, Okilink II, Faxable Facts, or contact Okidata Technical Support to find the correct part  
number. Refer to the Service Center Reference Guide for information on contacting Okidata.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 169  
Service Guide ML520/521  
Chapter B Illustrated Parts Listing  
B.2 CHARTS  
Below is an index to the illustrated parts breakdown charts.  
Section  
B.2.01  
B.2.02  
B.2.03  
B.2.04  
B.2.05  
B.2.06  
B.2.07  
B.2.08  
B.2.09  
B.2.10  
B.2.11  
B.2.12  
B.2.13  
Description  
Printer  
Upper Cover Assembly  
Printer General Assembly  
Printer Unit (1 of 3)  
Printer Unit (2 of 3)  
Printer Unit (3 of 3)  
Carriage Assembly  
Options  
Option Parts  
Consumables  
Packing Materials  
Documentation  
Service Training Kit Revision List  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 170  
Service Guide ML520/521  
Chapter B Illustrated Parts Listing  
Overview  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 171  
Service Guide ML520/521  
Chapter B Illustrated Parts Listing  
B.2.01 Printer  
Part numbers are subject to change. Refer to Okilink II for current part numbers and pricing information.  
Item  
Okidata P/N  
Oki-J P/N  
Description  
Comments Disassembly  
Refer to  
B.1.02  
Procedure  
1
2
3
4
62409001 N/A  
62409002 N/A  
62410001 N/A  
62410002 N/A  
Printer: ML520 Parallel  
(Epson/IBM/ML Comp.) 120 V  
N/A  
N/A  
N/A  
N/A  
Printer: ML520 Parallel  
(Epson/IBM/ML Comp.) 220 V  
Printer: ML521 Parallel  
(Epson/IBM/ML Comp.) 120 V  
Printer: ML521 Parallel  
(Epson/IBM/ML Comp.) 220 V  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 172  
Service Guide ML520/521  
Chapter B Illustrated Parts Listing  
B.2.02 Upper Cover Assembly  
Item  
Okidata P/N Oki-J  
P/N  
Description  
Comments Refer to Disassembly  
B.1.02  
Procedure  
1
1
2
2
3
53066902  
1PP4094-6501P2  
Cover: Upper  
(Narrow)  
RSPL 520  
3.2.06  
53067002  
1PP4094-7201P2  
Cover: Upper  
(Wide)  
RSPL 521  
RSPL 520  
RSPL 521  
RSPL 520  
3.2.06  
3.2.06  
3.2.06  
3.2.06  
51009401 N/A  
51009501 N/A  
Guide: Sheet  
(Narrow)  
Guide: Sheet  
(Wide)  
53067101  
2PA4094-7381G1  
Cover: Access  
(Narrow)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
3
53067201  
2PA4094-7382G1  
Cover: Access  
(Wide)  
RSPL 521  
3.2.06  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 173  
Service Guide ML520/521  
Chapter B Illustrated Parts Listing  
B.2.03 Printer General Assembly  
Item  
Okidata P/N Oki-J  
P/N  
Description  
Comments Refer to Disassembly  
B.1.02  
Procedure  
1
2
3
4
53562601  
2PP4094-6507P3  
Knob: Platen  
(ML500 Series)  
RSPL Both  
3.2.06  
53067301  
2PP4094-6506P1  
Cover: (B) for  
Card Slot  
RSPL Both  
RSPL Both  
RSPL Both  
3.2.06  
3.2.07  
N/A  
55072401  
4YA4042-1515G301  
PCB: FJIM (w/o  
ROM)  
56301702  
540A2036M1202  
Fuse: 2A 125V  
(GG52)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
5
55937502  
4YA4042-1516G2  
PCB: LEOP  
(Operator. Panel)  
RSPL Both  
RSPL Both  
3.2.09  
3.2.09  
3.2.08  
3.2.08  
3.2.08  
3.2.01  
3.2.02  
3.2.08  
3.2.08  
3.2.08  
6
53562703  
3PP4025-3670G3  
Panel: Operator  
7
56412401  
4YB4049-7030P1  
Transformer: 120 RSPL 520  
V ML520  
7
56412402  
4YB4049-7030P2  
Transformer: 120 RSPL 521  
V ML521  
8
55073201  
4YB4021-1143P1  
PCB: Filter 120 V RSPL Both  
9
56609701  
3YS4011-1315P1  
Cord: AC 120V  
RSPL Both  
10  
11  
12  
13  
50099501  
4YA4023-2801G1  
Printhead  
Assembly  
RSPL Both  
50707501  
4PP4025-3621P1  
Clamp: Cord  
RSPL Both  
56306201  
540A2062T2102  
Fuse: 1A 250V  
(Filter Brd 220V)  
Option RSPL Both  
RSPL Both  
56306101  
540A2067T1252  
Fuse: 2.5A 125V  
(Filter Board)  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 174  
Service Guide ML520/521  
Chapter B Illustrated Parts Listing  
B.2.04 Printer Unit  
Item  
Okidata P/N Oki-J  
Description  
Comments Refer to Disassembly  
P/N  
B.1.02  
Procedure  
1
1
2
3
4
5
53563101  
3PA4025-3720G1  
Frame: Main  
(Narrow)  
RSPL 520  
3.2.30  
53563201  
3PA4025-3721G1  
Frame: Main  
(Wide)  
RSPL 521  
RSPL Both  
RSPL Both  
RSPL Both  
RSPL Both  
3.2.30  
3.2.27  
3.2.27  
3.2.18  
3.2.18  
50804601  
3PP4025-3315P1  
Lever: Bottom  
Paper End  
50804701  
3PP4025-3322P1  
Lever: Bottom  
Sensor  
50804801  
3PP4025-3321P1  
Lever: Rear  
Sensor  
50804902  
Lever: Sensor  
4PP4025-3323P2  
(Cut  
Sheet/Continuous  
)
Download from Www.Somanuals.com. All Manuals Search And Download.  
6
56627201  
3PB4025-3356P1  
Cord: Connection  
Line Feed  
RSPL Both  
RSPL Both  
RSPL Both  
RSPL Both  
RSPL 520  
RSPL 521  
RSPL Both  
RSPL 520  
RSPL 521  
RSPL Both  
RSPL Both  
RSPL 520  
RSPL 521  
RSPL 520  
RSPL 521  
RSPL Both  
3.2.21  
3.2.21  
3.2.21  
3.2.16  
3.2.26  
3.2.26  
3.2.15  
3.2.13  
3.2.13  
3.2.13  
3.2.15  
3.2.15  
3.2.15  
3.2.25  
3.2.25  
3.2.25  
7
56510302  
3PB4025-3357P2  
Motor: Line Feed  
Assembly  
8
51228601  
3PB4055-2893P1  
Gear: Line Feed  
Idle  
9
51010301  
3PA4025-3387G1  
Plate: Left  
Ground  
10  
10  
11  
12  
12  
13  
14  
15  
15  
16  
16  
17  
50923001  
3PP4025-3320P1  
Spring: Leaf  
(Narrow)  
50923101  
3PP4025-3507P1  
Spring: Leaf  
(Wide)  
53067701  
3PP4025-3380P1  
Cam: Adjust  
53563301  
3PP4025-3376P1  
Rack: Space  
(Narrow)  
53563401  
3PP4025-3522P1  
Rack: Space  
(Wide)  
50923501  
4PB4025-3377P1  
Spring: Tension  
(Space Rack)  
51009701  
4PP4025-3378P1  
Guide: Rail  
Ground Clip  
51009801  
3PP4025-3379P1  
Guide: Rail  
(Narrow)  
51009901  
3PP4025-3523P1  
Guide: Rail  
(Wide)  
53563501  
4PP4025-3381P1  
Shaft: Carriage  
(Narrow)  
53563502  
4PP4025-3381P2  
Shaft: Carriage  
(Wide)  
53067601  
4PA4025-3382G1  
Protector:  
Support  
(Assembly)  
18  
50923601  
4PB4025-3385P1  
Spring: Support  
Protect Reset  
RSPL Both  
3.2.25  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 175  
Service Guide ML520/521  
Chapter B Illustrated Parts Listing  
B.2.05 Printer Unit  
Item  
Okidata P/N Oki-J  
Description  
Comments Refer to Disassembly  
P/N  
B.1.02  
Procedure  
1
1
2
3
4
53563101  
3PA4025-3720G1  
Frame: Main  
(Narrow)  
RSPL 520  
3.2.30  
53563201  
3PA4025-3721G1  
Frame: Main  
(Wide)  
RSPL 521  
RSPL Both  
RSPL Both  
RSPL Both  
3.2.30  
3.2.29  
3.2.29  
3.2.24  
51228001  
4PP4025-3340P1  
Gear: Change  
Gear: Tractor  
Cam: Release  
51228101  
3PP4025-3341P1  
50805301  
3PP4025-3352P1  
Download from Www.Somanuals.com. All Manuals Search And Download.  
5
51228201  
4PP4025-3353P1  
Gear: Idle  
RSPL Both  
RSPL Both  
RSPL Both  
RSPL Both  
RSPL 520  
RSPL 521  
RSPL 520  
RSPL 521  
3.2.23  
3.2.23  
3.2.22  
3.2.17  
3.2.19  
3.2.19  
3.2.05  
3.2.05  
6
50805101  
2PP4025-3354P1  
Lever: Change  
Spring: Reset  
7
50923201  
3PP4025-3355P1  
8
51010201  
3PP4025-3386P1  
Plate: Right  
Ground  
9
50098301  
3PA4025-3370G1  
Platen Assembly  
(Narrow)  
9
50098302 N/A  
Platen Assembly  
(Wide)  
10  
10  
53341501  
3PA4025-3440G2  
Roller: Pull Up  
Assembly (N)  
53341601  
3PA4025-3530G2  
Roller: Pull Up  
Assembly (W)  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 176  
Service Guide ML520/521  
Chapter B Illustrated Parts Listing  
B.2.06 Printer Unit  
Item  
Okidata P/N Oki-J  
Description  
Comments Refer to Disassembly  
P/N  
B.1.02  
Procedure  
1
1
2
53563101  
3PA4025-3720G1  
Frame: Main  
(Narrow)  
RSPL 520  
3.2.30  
53563201  
3PA4025-3721G1  
Frame: Main  
(Wide)  
RSPL 521  
RSPL 520  
3.2.30  
3.2.28  
50922901  
4PP4025-3316P1  
Spring: Front  
Pressure  
(Narrow)  
3
50922801  
Spring: Front  
RSPL 521  
3.2.28  
4PP4025-3324P1  
Pressure (Wide)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
4
5
6
53341101  
4PP4025-3317P1  
Holder: Front  
Roller  
RSPL Both  
RSPL Both  
RSPL 520  
3.2.28  
3.2.28  
3.2.27  
53341202  
4PP4025-3327G1  
Roller: Front  
Pressure  
51227801  
3PP4025-3318P1  
Shaft: Front  
Release Gear  
(Narrow)  
6
51227901  
3PP4025-3505P1  
Shaft: Front  
Release Gear  
(Wide)  
RSPL 521  
3.2.27  
7
7
8
8
9
50097301 N/A  
Pan: Paper  
(Narrow)  
RSPL 520  
RSPL 521  
RSPL 520  
RSPL 521  
RSPL Both  
3.2.27  
3.2.27  
3.2.24  
3.2.24  
3.2.24  
50097401  
1PP4025-3506P2  
Pan: Paper  
(Wide)  
50923301  
3PP4025-3346G1  
Spring: Pressure  
(Narrow)  
50923401  
3PP4025-3511G1  
Spring: Pressure  
(Wide)  
50805201  
Lever: Switch  
4PP4025-3351P1  
(Cut  
Sheet/Continuous  
)
10  
11  
12  
51228301  
4PP4025-3350P1  
Arm: Front  
Release Gear  
RSPL Both  
RSPL Both  
RSPL 520  
3.2.24  
3.2.20  
3.2.20  
50924701  
4PP4025-3386P1  
Spring: Lock  
50097701  
3PA4025-3360G2  
Paper Chute  
Assembly  
(Narrow)  
12  
13  
13  
14  
50097801  
3PA4025-3515G2  
Paper Chute  
Assembly (Wide)  
RSPL 521  
RSPL 520  
RSPL 521  
RSPL 520  
3.2.20  
3.2.20  
3.2.20  
3.2.29  
53341301  
3PB4025-3364P1  
Roller: Pressure  
Rear (Narrow)  
53341401  
3PB4025-3517P1  
Roller: Pressure  
Rear (Wide)  
50097501  
Tractor:  
3PA4025-3330G1  
Assembly  
(Narrow)  
14  
50097502  
Tractor:  
RSPL 521  
3.2.29  
3PA4025-3330G2  
Assembly (Wide)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 177  
Service Guide ML520/521  
Chapter B Illustrated Parts Listing  
B.2.07 Carriage Assembly  
Item  
Okidata P/N Oki-J  
P/N  
Description  
Comments Refer to Disassembly  
B.1.02  
Procedure  
1
2
3
50707401  
3PP4025-3431P1  
Clamp: Head  
Protector: Ribbon  
RSPL Both  
3.2.02  
53562801  
3PP4025-3430P1  
RSPL Both  
RSPL Both  
3.2.03  
3.2.04  
51228501  
3PA4025-3406G1  
Gear: Case  
(Assembly)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
4
56729601  
224A1285P0400  
Connector: PC  
HD40  
RSPL Both  
RSPL Both  
RSPL Both  
RSPL Both  
Both Inc. 9 10 11  
Both  
3.2.10  
3.2.11  
3.2.11  
3.2.11  
3.2.11  
3.2.11  
3.2.11  
5
53343001  
4PP4025-3433P1  
Holder:  
Connector (L)  
6
53343101  
4PP4025-3434P1  
Holder Connector  
(R)  
7
56510401  
4YA4025-3250G1  
Motor: Space  
(Assembly)  
8
53343301  
4PA4025-3719G1  
Guide: Roller  
Assembly  
9
53341901  
4PP4025-3398P1  
Roller: Guide  
10  
53342001  
3PP4025-3399P1  
Holder: Guide  
Roller  
Both  
11  
12  
N/A N/A  
Pin  
Both  
Both  
3.2.11  
3.2.11  
N/A 4PP4025-3401P1 Guide Roller  
Spring  
13  
13  
14  
56627301  
2PU4007-1193P1  
Cable: Carriage  
(Narrow)  
RSPL 520  
3.2.12  
3.2.12  
3.2.14  
56627302 N/A  
Cable: Carriage  
(Wide)  
RSPL 521  
53343201  
4PA4025-3718G1  
Assembly:  
Roller/Holder  
Backup  
Both Inc. 15 16 17  
15  
16  
53341701  
4PP4025-3392P1  
Roller: Back Up  
Both  
Both  
3.2.14  
3.2.14  
53341801  
3PP4025-3393P1  
Holder: Back Up  
Roller  
17  
18  
N/A N/A  
Pin  
Both  
Both  
3.2.14  
3.2.14  
50925001  
3PP4025-3397P1  
Holder: Backup  
Roller Spring  
19  
50098901  
4PP4025-3394G1  
Carriage: Frame  
Set  
RSPL Both  
3.2.25  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 178  
Service Guide ML520/521  
Chapter B Illustrated Parts Listing  
B.2.08 Options  
Item  
Okidata P/N Oki-J  
Description  
Comments Refer to Disassembly  
P/N  
B.1.02  
Procedure  
1
1
2
2
3
70022501 N/A  
Kit: Single Bin  
CSF 5000 Narrow  
Option 520  
N/A  
70022701 N/A  
70023001 N/A  
70023201 N/A  
70022901 N/A  
Kit: Single Bin  
CSF 5001 Wide  
Option 521  
Option 520  
Option 521  
Option 520  
N/A  
N/A  
N/A  
N/A  
Kit: Pull Tractor  
Narrow  
Kit: Pull Tractor  
Wide  
Kit: Push Tractor  
(Bottom) Narrow  
Download from Www.Somanuals.com. All Manuals Search And Download.  
3
4
5
70023101 N/A  
70023301 N/A  
70000803 N/A  
Kit: Push Tractor  
(Bottom) Wide  
Option 521  
Option 520  
Option Both  
N/A  
N/A  
N/A  
Kit: Roll Paper  
Stand  
Kit: Parallel  
Interface  
Plug'n'Play  
Accessory  
6
7
70012801 N/A  
Kit: RS232-C  
Serial Interface  
Option Both  
N/A  
N/A  
56412501  
4YB4049-7031P1  
Transformer  
230-240V  
(ML520)  
Option RSPL 520  
7
8
56412502  
4YB4049-7031P2  
Transformer  
230-240V  
(ML521)  
Option RSPL 521  
Option RSPL Both  
N/A  
N/A  
56624101  
3YS4011-1265P1  
Cord: AC (220V)  
ML Series Right  
Angle  
8
56624401  
3YS4011-1268P1  
Cord: AC 240V  
Option RSPL Both  
Option RSPL Both  
Option RSPL Both  
N/A  
N/A  
N/A  
9
55038901  
4YA4021-1050G1  
PCB: LXHI  
(RS232-C)  
10  
56306001  
4YB4021-1146P1  
Fuse: 3.15A for  
230/240V Power  
Supply  
11  
11  
12  
55073301  
4YB4021-1144P1  
PCB: Filter 230 V Option RSPL Both  
N/A  
N/A  
N/A  
55073302  
4YB4021-1144P2  
PCB: Filter 240 V Option RSPL Both  
56306201  
Fuse: 1A 250V  
Option RSPL Both  
540A2062T2102  
(Filter Brd 220V)  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 179  
Service Guide ML520/521  
Chapter B Illustrated Parts Listing  
B.2.09 Option Parts  
Item  
Okidata P/N Oki-J  
Description  
Comments Refer to Disassembly  
P/N  
B.1.02  
Procedure  
1
50097901 N/A  
Tractor: Pull and  
Bottom Assembly  
(Right)  
Option RSPL Both  
N/A  
2
3
3
50098001  
4PA4025-3608G1  
Tractor: Pull and  
Bottom Assembly  
(Left)  
Option RSPL Both  
Option RSPL 520  
Option RSPL 521  
N/A  
N/A  
N/A  
50098101  
2PP4094-7383G1  
Tractor: Cover  
Assembly (N) Pull  
Tractor  
50098201  
2PP4094-7384G1  
Tractor: Cover  
Assembly (W)  
Pull Tractor  
4
5
6
50098501  
2PA4094-6510G1  
Stand: Bottom  
Push (Right)  
Option RSPL Both  
Option RSPL Both  
Option RSPL 520  
N/A  
N/A  
N/A  
50098502  
2PA4094-6510G4  
Stand: Bottom  
Push (Left)  
50098701  
4PP4094-7385G1  
Knife: Paper (N)  
Bottom Push  
Tractor  
6
7
7
8
50098801  
4PP4094-7386G1  
Knife: Paper (W)  
Bottom Push  
Tractor  
Option RSPL 521  
Option RSPL 520  
Option RSPL 521  
Option RSPL Both  
N/A  
N/A  
N/A  
N/A  
51010001  
1PP4053-2570P1  
Guide: Front  
Sheet (N)  
Cut-Sheet Feeder  
51010101  
1PP4053-2571P2  
Guide: Front  
Sheet (W)  
Cut-Sheet Feeder  
53067401  
1PP4053-2574P1  
Cover: Side  
(Left) Cut-Sheet  
Feeder  
Download from Www.Somanuals.com. All Manuals Search And Download.  
8
9
9
53067501  
1PP4053-2575P1  
Cover: Side  
(Right) Cut-Sheet  
Feeder  
Option RSPL Both  
Option RSPL 521  
Option RSPL 520  
N/A  
N/A  
N/A  
53480901  
1PP4043-1891P4  
Supporter: Front  
Sheet (W)  
Cut-Sheet Feeder  
53562901  
1PP4053-2576P1  
Supporter: Front  
Sheet (N)  
Cut-Sheet Feeder  
10  
11  
12  
13  
14  
15  
16  
17  
53563001  
4PP4053-2547G1  
Shoe: Brake  
Cut-Sheet Feeder  
Option RSPL Both  
Option RSPL Both  
Option RSPL Both  
Option RSPL Both  
Option Both  
N/A  
N/A  
N/A  
N/A  
N/A  
N/A  
N/A  
N/A  
55937301  
4YA4053-3025G1  
PCB: NCSF  
Cut-Sheet Feeder  
56510501  
3PB4050-2560P1  
Motor: Pulse  
Cut-Sheet Feeder  
56627501  
3YS4011-5120G1  
Cable: CSF  
Cut-Sheet Feeder  
50062801  
4PB4053-1705G1  
Roller: Hopping  
(L.H.) CSF  
50062802  
4PB4053-1705G2  
Roller: Hopping  
(R.H.) CSF  
Option Both  
53321501  
3PB4025-1941P1  
Support: Rear  
Sheet CSF  
Option Both  
53448501  
4PB4025-1914P1  
Sheet: Friction  
CSF  
Option Both  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 180  
Service Guide ML520/521  
Chapter B Illustrated Parts Listing  
B.2.10 Consumables  
52107001 N/A Ribbon: Black Consumable Both 3.2.02  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 181  
Service Guide ML520/521  
Chapter B Illustrated Parts Listing  
B.2.11 Packing Materials  
Item  
Okidata P/N Oki-J  
P/N  
Description  
Comments Refer Disassembly  
to B.1.02  
Procedure  
1
1
2
3
53565101 N/A  
53565201 N/A  
53565401 N/A  
53565402 N/A  
Box: Graphic (ML520) RSPL 520  
N/A  
Box: Graphic (ML521)  
Foam: Molded (Left)  
Foam: Molded (Right)  
RSPL 521  
RSPL Both  
RSPL Both  
N/A  
N/A  
N/A  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 182  
Service Guide ML520/521  
Chapter B Illustrated Parts Listing  
B.2.12 Documentation  
Item  
Okidata P/N Oki-J  
P/N  
Description  
Comments Refer Disassembly  
to B.1.02  
Procedure  
1#  
58229401 N/A  
58229402 N/A  
58229403 N/A  
58232501 N/A  
52033001 N/A  
53436029 N/A  
52050809 N/A  
58059501 N/A  
59256801 N/A  
58232502 N/A  
52033001 N/A  
53436029 N/A  
52050809 N/A  
58059501 N/A  
58306101 N/A  
Kit: ML520/521  
Service Training  
Document Both  
N/A  
1#  
Kit: ML520/521  
Service Training  
Document Both  
Document Both  
N/A  
N/A  
N/A  
N/A  
N/A  
N/A  
N/A  
N/A  
N/A  
N/A  
N/A  
N/A  
N/A  
N/A  
1#  
Kit: ML520/521  
Service Training  
2 A  
3 A  
4 A  
5 A  
6 A  
7 A  
2 B  
3 B  
4 B  
5 B  
6 B  
7 B  
Package: User's  
Documentation  
Document Inc. 3  
4 5 6 7  
Card: QA Reply  
Bag: Poly 9" x 12"  
Card: Request  
Document Part of  
2 A  
Document Part of  
2 A  
Document Part of  
2 A  
Card: Registration  
Handbook: Printer  
Document Part of  
2 A  
Document Part of  
2 A  
Package: User's  
Documentation  
Document Inc. 3  
4 5 6 7 8  
Card: QA Reply  
Bag: Poly 9" x 12"  
Card: Request  
Document Part of  
2 B  
Document Part of  
2 B  
Document Part of  
2 B  
Card: Registration  
Document Part of  
2 B  
Sheet: Printer  
Handbook Errata  
Document Part of  
2 B  
Download from Www.Somanuals.com. All Manuals Search And Download.  
8 B  
59256802 N/A  
Handbook: Printer  
Document Part of  
2 B  
N/A  
9
59258401 N/A  
59261000 N/A  
Manual: Maintenance  
Document Both  
Document Both  
N/A  
N/A  
10  
Manual:  
Troubleshooting  
11  
59254001 N/A  
Product Specifications  
Document Both  
N/A  
* To order Marketing Literature, complete an Okidata Marketing Literature Order Form. Fax the  
completed form to Okidata Marketing Communications.  
* * Obtain this form by faxing a request to Okidata Marketing Communications. Refer to the Service  
Center Reference Guide for information on contacting Okidata.  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Page: 183  
Service Guide ML520/521  
Chapter B Illustrated Parts Listing  
B.2.13 Service Training Kit Revision List  
P/N 58229401 Microline 520/521 Service Training Kit  
This kit was replaced by P/N 58229402.  
Items in the training kit (except for the Printer Handbook) are NOT available separately.  
Item  
Okidata P/N Oki-J  
P/N  
Description  
Comments Refer Disassembly  
to B.1.02  
Procedure  
1 A  
58229401 N/A  
Kit: ML520/521  
Service Training  
Document Both  
N/A  
2 A  
3 A  
52063201 N/A  
58229501 N/A  
Label: Box  
Document  
Document  
N/A  
N/A  
Administration  
Package  
4 A  
58090301 N/A  
Envelope:  
Document  
N/A  
Administration  
Package  
5 A  
6 A  
7 A  
58090401 N/A  
59257701 N/A  
58090501 N/A  
Cover Letter  
Document  
Document  
Document  
N/A  
N/A  
N/A  
Training Guide  
Printhead Gap  
Adjustment Material  
8 A  
9 A  
58090601 N/A  
58090701 N/A  
Certification Test  
Document  
Document  
N/A  
N/A  
Certification Test  
Answer Sheet  
10 A  
11 A  
58090801 N/A  
58090901 N/A  
Course Critique  
Document  
Document  
N/A  
N/A  
Envelope: Pre-Printed  
Return  
12 A  
13 A  
59257801 N/A  
59257901 N/A  
Service Handbook  
Document  
N/A  
N/A  
User's Documentation  
Document Incl 14  
A
14 A  
15 A  
59256801 N/A  
57519801 N/A  
Handbook: Printer  
Service Videotape  
Document Both  
Document  
N/A  
N/A  
Download from Www.Somanuals.com. All Manuals Search And Download.  
16 A  
17 A  
18 A  
19 A  
20 A  
52063202 N/A  
52063203 N/A  
52063204 N/A  
57517101 N/A  
53533001 N/A  
Label: Service  
Videotape Case  
Document  
Document  
Document  
Document  
Document  
N/A  
N/A  
N/A  
N/A  
N/A  
Label: Service  
Videotape Front  
Label: Service  
Videotape Spine  
Red Vinyl Case (VHS  
Videotape)  
Storage Box  
P/N 58229402 Microline 520/521 Service Training Kit  
This kit was replaced by P/N 58229403.  
Items in the training kit (except for the Printer Handbook) are NOT available separately.  
Item  
Okidata P/N Oki-J  
P/N  
Description  
Comments Refer Disassembly  
to B.1.02  
Procedure  
1 B  
58229402 N/A  
Kit: ML520/521  
Service Training  
Document Both  
N/A  
2 B  
3 B  
4 B  
5 B  
52063205 N/A  
58090402 N/A  
59257802 N/A  
59257901 N/A  
Label: Box  
Document Both  
Document Both  
Document Both  
N/A  
N/A  
N/A  
N/A  
Read Me First  
Service Handbook  
User's Documentation  
Document Incl 6  
B
6 B  
7 B  
8 B  
59256801 N/A  
57519801 N/A  
52063204 N/A  
Printer Handbook  
Service Videotape  
Document Both  
Document Both  
Document Both  
N/A  
N/A  
N/A  
Label: Service  
Videotape Spine  
9 B  
53570401 N/A  
Sleeve: Videotape  
(Cardboard)  
Document Both  
N/A  
P/N 58229403 Microline 520/521 Service Training Kit  
This kit was replaced by P/N 58229402.  
Items in the training kit (except for the Printer Handbook) are NOT available separately.  
Download from Www.Somanuals.com. All Manuals Search And Download.  
Item  
Okidata P/N Oki-J  
P/N  
Description  
Comments Refer Disassembly  
to B.1.02  
Procedure  
1 C  
58229403 N/A  
Kit: ML520/521  
Service Training  
Document Both  
N/A  
2 C  
3 C  
4 C  
5 C  
6 C  
52063206 N/A  
58090403 N/A  
59257803 N/A  
59256802 N/A  
58306101 N/A  
Label: Box  
Document Both  
Document Both  
Document Both  
Document Both  
Document Both  
N/A  
N/A  
N/A  
N/A  
N/A  
Read Me First  
Service Handbook  
Printer Handbook  
Sheet: Printer  
Handbook Errata  
7 C  
8 C  
57519802 N/A  
Service Videotape  
Document Both  
Document Both  
N/A  
N/A  
52063204 Rev B N/A Label: Service  
Videotape Spine  
9 C  
53570401 N/A  
Sleeve: Videotape  
(Cardboard)  
Document Both  
N/A  
Copyright 1997, Okidata, Division of OKI America, Inc. All rights reserved. See the OKIDATA Business  
Partner Exchange (BPX) for any updates to this material. (http://bpx.okidata.com)  
Download from Www.Somanuals.com. All Manuals Search And Download.  

Milwaukee Sander HEAVY DUTYSANDERS User Manual
National Mower Lawn Mower HY70OM 8 992 User Manual
NEC Projector LT155 User Manual
NETGEAR Network Router DG834GT GTB User Manual
Nikon Two Way Radio MH 60 User Manual
NordicTrack Home Gym NTEL11990 User Manual
Olympus Camera Lens f28 35 User Manual
Oreck Vacuum Cleaner U3771 User Manual
Palsonic DVD Player DVD2060DX User Manual
Patton electronic Network Card IM 1 F User Manual