Yamaha Musical Instrument Amplifier Bass Amplifier User Manual
BASS AMPLIFIER  
SERVICE MANUAL  
CONTENTS  
SPECIFICATIONS .............................................................................. 3  
PANEL LAYOUT.................................................................................. 3  
CIRCUIT BOARD LAYOUT................................................................. 4  
BLOCK DIAGRAM .............................................................................. 4  
DISASSEMBLY PROCEDURE ........................................................... 5  
CIRCUIT BOARDS ............................................................................. 7  
IC BLOCK DIAGRAM.......................................................................... 8  
INSPECTIONS .................................................................................... 8  
PARTS LIST  
OVERALL CIRCUIT DIAGRAM  
This document is printed on chlorine free (ECF) paper with soy ink.  
GA  
20010720-17800  
011592  
HAMAMATSU, JAPAN  
1.507K-033 K  
Printed in Japan 2001.08  
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F-20B  
SPECIFICATIONS  
Rated Output Power:  
20W  
Speaker:  
25cm x 1  
Controls:  
VOLUME, TREBLE, HIGH  
MID, LOW MID, BASS,  
Input Level Select Switch  
(PASSIVE/ACTIVE)  
Input/Output Terminals: INPUT, AUX IN, PHONES  
Power Consumption:  
25W/120V (UL, CSA)  
25W/230V (E, BS)  
U.S. and Canadian mod-  
els: 120V, 60Hz  
Power Requirements:  
General model: 230V,  
50Hz  
Dimensions (W x H x D) : 357 x 453 x 242mm (14.1"  
x 17.8" x 9.5")  
Weight:  
10.5kg (23 lbs 2 oz)  
PANEL LAYOUT  
ᕡ
ᕢ
ᕣ
ᕤ
ꢀ
ꢁ
ꢂ
ꢃ ꢄ  
ꢅ
ꢆ
ᕡ INPUT  
ᕢ PASSIVE/ACTIVE (Input Level Select Switch)  
ᕣ VOLUME  
* No sound is produced when the VOLUME knob  
is set to "0".  
ACTIVE EQUALIZER  
ᕤ TREBLE  
ꢀ HIGH MID  
ꢁ LOW MID  
ꢂ BASS  
ꢃ POWER INDICATOR  
* The lamp will light when the amplifier's power  
switch is ON.  
ꢄ AUX IN  
* Use the volume control on the audio device to  
control its volume level.  
ꢅ PHONES  
* The speaker will produce no sound when a pair  
of headphones is connected to this jack.  
ꢆ POWER  
3
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F-20B  
CIRCUIT BOARD LAYOUT  
ꢀ Top View  
ꢀ Side View  
AC Cord  
MAIN 2/2  
Power Transformer  
MAIN 2/2  
MAIN 1/2  
MAIN 1/2  
ꢀ Front View  
MAIN 1/2  
BLOCK DIAGRAM  
MAIN 1/2  
GAIN SELECT  
ACTIVE CH.  
PASSIVE CH.  
AUX IN  
+12V  
8
JK3  
SW2  
INPUT  
2
1
5
7
ACTIVE TYPE  
TONE CONTROL  
IC3  
IC3  
4
IC1,IC2  
VOLUME  
VR1  
OP AMP  
-12V  
JK1  
+12V  
MAIN 2/2  
8
IC1  
4
+B  
5
3
1
VR5  
VR4  
VR3  
VR2  
1
4
IC4  
-12V  
POWER  
AMP  
3
OP AMP  
-B  
POWER SWITCH  
SW1  
FUSE  
FZ1  
T1  
T2  
PHONE  
CN2 4P  
+B  
+12V  
-12V  
-B  
POWER SUPPLY CIRCUIT  
JK2  
T3  
T4  
4Ω Speaker  
GND  
T1  
G
U, C, S, BS  
T2  
POWER TRANSFORMER  
4
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F-20B  
DISASSEMBLY PROCEDURE  
1.  
Pre-Main Unit (Time required: about 2 min)  
1-1 Remove the eight (8) screws marked [A]. The back  
board can then be removed. (Fig.1)  
1-2 Pull out the speaker wires. (Fig.1)  
1-3 Remove the four (4) screws marked [30]. The pre-  
main unit can then be removed by sliding it  
backward. (Fig.1)  
2.  
Speaker (Time required: about 2 min)  
2-1 Remove the back board. (See Procedure 1-1)  
2-2 Pull out the speaker wires. (Fig.1)  
2-3 Remove the four (4) screws marked [60a]. The  
speaker can then be removed. (Fig.1)  
3.  
MAIN 1/2 Circuit Board  
(Time required: about 4 min)  
3-1 Remove the pre-main unit. (See Procedure 1)  
3-2 Remove the five (5) knobs marked [P100] and the  
five (5) hexagonal nuts marked [C]. (Fig.5)  
3-3 Remove the hexagonal nut marked [A120] and the  
hexagonal nut marked [A140]. (Fig.5)  
3-4 Push the hooks of the spacer support (at the arrow  
symbol area of illustration) with a needle-nose plier  
to unlock.  
The MAIN 1/2 circuit board can then be removed.  
Pre-Main Unit  
Pre-Main Unit  
Speaker  
(Fig.2)  
[60a]  
[30] x 4  
(Fig.1)  
BackBoard  
[A]  
[30]: Truss Head Screw 4.0X25 MFZN2BL (VN347600)  
[A]: Bind Head Tapping Screw 4.0X25 FCRM3-BL (EI340256)  
[60a]: Bind Head Screw (VB403600)  
Needle-nose plier  
[P40]  
MAIN1/2 Circuit Board  
(Fig. 2)  
5
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F-20B  
4.  
MAIN 2/2 Circuit Board  
(Time required: about 3 min)  
4-1 Remove the pre-main unit. (See Procedure 1)  
4-2 Remove the screw marked [C80]. The MAIN 2/2  
circuit board can then be removed. (Fig.3, Fig.5)  
5.  
Power Transformer (Time required: about 4 min)  
5-1 Remove the pre-main unit. (See Procedure 1)  
5-2 While holding the nuts marked [P70] with a  
spanner, remove the two (2) screws marked [P60].  
The power transformer can then be removed.  
(Fig.4)  
MAIN1/2 Circuuit Board  
[P70]  
[P60]  
Power Transformer  
[P80]  
MAIN1/2 Circuuit Board  
(Fig. 3)  
(Fig.4)  
Power Transformer  
MAIN 2/2  
[P40]  
[P80] [P70] [P60]  
[P40][P60] [P70]  
MAIN 1/2  
[A120]  
[P100], [C]  
[A140]  
[A120]: Hexagonal Nut 9.0 12X2 MFNI33 (LX200060)  
[A140]: Hexagonal Nut 12.0 14X2 MFNI33 (ES200210)  
[P60]: Pan Head Screw 4.0X10 MFZN2BL (V7018000)  
[P70]: Hexagonal Nut #1 4.0 MFZN2Y (VB837300)  
[P80]: Bind Head Screw-1 3.0X16 MFZN2BL (V7018100)  
[P100]: Knob (V6955100)  
(Fig. 5)  
6
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F-20B  
A
CIRCUIT BOARDS  
ꢀ MAIN1/2 CIRCUIT BOARD  
GAIN  
INPUT  
VOLUME  
TREBLE  
SELECT  
A'  
A
to POWER  
TRANSFORMER  
to POWER SW  
from POWER  
TRANSFORMER  
to MAIN 2/2 CN4  
from AC CORD  
FUSE  
RATE  
VERSION  
INDICATION  
J, U  
250V 315mAL  
250V T160mAL  
Must be  
erased  
Must be  
erased  
E, BS  
POWER  
HIGH MID  
LOW MID  
BASS  
AUX IN PHONES  
Component side  
to SPEAKER  
A'  
ꢀ MAIN2/2 CIRCUIT BOARD  
MAIN 1/2 (J, U, C): CNA-V755470  
MAIN 1/2 (H, B): CNA-V755480  
MAIN 2/2 (J, U, C): CNA-V755470  
MAIN 2/2 (H, B): CNA-V755480  
to MAIN 1/2 CN5  
Component side  
7
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F-20B  
IC BLOCK DIAGRAM  
BA4558 (XO078A00)  
Dual Operational Amplifier  
MAIN: IC1,IC2,IC3  
+DC Voltage  
Supply  
Output A  
1
2
3
4
+V  
8
7
6
5
Inverting  
Input A  
Output B  
+
-
Inverting  
Input B  
Non-Inverting  
Input A  
+
-
Non-Inverting  
Input B  
-DC Voltage Supply  
-V  
INSPECTIONS  
1.  
Preparation  
To inspect the main unit, the following jigs are  
required.  
CD player  
Headphones  
Before turning the power on, set all the knobs on  
the panel to "0".  
Raise the Input Level Select Switch to select  
[PASSIVE] position.  
2.  
3.  
Power supply  
Connect the power cord to the suitable power  
supply socket for each version.  
(UC-120V, E&BS-220V)  
Inspection procedure  
3-1 Input the audio signal of CD player to the [AUX IN]  
jack.  
3-2 Make sure that rotating the [VOLUME] knob to the  
right (or left) makes the sound gradually larger (or  
smaller).  
3-3 Make sure that rotating the [TREBLE] knob to the  
right (or left) boosts (or cuts) the high frequency.  
3-4 Make sure that rotating the [HIGH MID] knob to  
the right (or left) boosts (or cuts) the upper-middle  
frequency.  
3-5 Make sure that rotating the [LOW MID] knob to  
the right (or left) boosts (or cuts) the lower-middle  
frequency.  
3-6 Make sure that rotating the [BASS] knob to the  
right (or left) boosts (or cuts) the low frequency.  
3-7 Make sure that the sound becomes smaller when  
you depress the Input Level Select Switch to select  
[ACTIVE] position.  
3-8 Raise the Input Level Select Switch again to select  
[PASSIVE] position. Make sure that the audio  
signal sounds over the speaker.  
3-9 Connect the headphones to the [PHONES] jack.  
Make sure that the speaker produces no sound and  
the audio signal sounds over the headphones.  
3-10 Set all the knobs on the panel to "0" and finish the  
inspection.  
8
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F-20B  
BASS AMPLIFIER  
PARTS LIST  
CONTENS  
OVERALL ASSEMBLY ..................................................................................2  
PRE-MAIN UNIT ............................................................................................4  
ELECTRICAL PARTS ....................................................................................6  
Note) DESTINATION ABBREVIATIONS  
A: Australian model  
B: British model  
M: South African model  
O: Chinese model  
C: Canadian model  
D: German model  
E: European model  
F: French model  
Q: South-east Asia model  
T: Taiwan model  
U: U.S.A. model  
V: General export model (110V)  
W: General export model (220V)  
N,X: General export model  
Y: Export model  
H: North European model  
I:  
Indonesian model  
J: Japanese model  
WARNING  
Components having special characteristics are marked  
specifications equal to those originally installed.  
and must be replaced with parts having  
The numbers in “QTY” shows quantities for each unit.  
The parts with “--” in “Part No.” are not available as spare parts.  
The second letter of the shaded (  
The second letter of the shaded (  
) part number is I, not one.  
) part number is O, not zero.  
1
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F-20B  
OVERALL ASSEMBLY  
Pre-Main Unit  
20  
50  
30  
40  
C60  
C50  
C60  
C50  
C40  
C30  
60a  
C20  
60  
C30  
C100  
C110  
A
C70  
C90  
C80  
10  
Overall Cabinet Assembly  
2
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F-20B  
REF NO. PART NO.  
DESCRIPTION  
REMARKS  
QTY RANK  
OVERALL ASSEMBLY  
Overall Assembly  
Overall Assembly  
Overall Assembly  
Overall Assembly  
F-20B  
J
U,C  
H
B
--  
--  
--  
--  
(V745880)  
(V745890)  
(V745900)  
(V745910)  
*
10 V7461100 Overall Cabinet Assembly  
20  
20  
20  
20  
--  
--  
--  
--  
Pre-Main Unit  
Pre-Main Unit  
Pre-Main Unit  
Pre-Main Unit  
J
U,C  
H
(V745930)  
(V745940)  
(V745950)  
(V745960)  
B
30 VN347600 Truss Head Screw  
40 ET500040 Flat Washer  
4.0X25 MFZN2BL  
4.0X10X0.8 MFZN2BL  
4
4
01  
01  
50  
50  
50  
--  
--  
--  
Label  
Label  
Label  
J
U,C  
H,B  
(V745970)  
(V745980)  
(V745990)  
*
*
60 XO361A00 Speaker Unit  
60a VB403600 Bind Head Screw  
4ohm 30W  
4
6
01  
01  
OVERALL CABINET ASSEMBLY  
V7461100 Overall Cabinet Assembly  
-- Cabinet Assembly  
F-20B  
C10  
(V746050)  
C20 V5969000 Corner Protector  
C30 21770200 Oval Head Screw  
C40 V6327200 Handle  
C50 V6327300 Handle Holder  
C60 V7017900 Oval Head Screw  
C70 V6327400 Foot  
3.0X12 MFZN2BL  
KPBO KAH1D-205  
KPBO KAH3D400-A  
4.0X25 MFZN2BL  
KPBO KRRU19  
12 01  
2
2
4
4
4
01  
01  
01  
C80 EP030310 Bind Head Tapping Screw-1  
C90 03765580 Flat Washer  
3.0X16 MFZN2BL  
3.0X8X0.5 MFZN2BL  
C100 V7363300 Name Plate  
C110 VN729100 Bind Head Tapping Screw-1  
3.0X10 MFZN2BL  
4.0X25 FCRM3-BL  
2
8
01  
01  
A
EI340256 Bind Head Tapping Screw  
*New parts  
RANK: Japan only  
3
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F-20B  
PRE-MAIN UNIT  
A100  
A110  
A120  
A10  
A70  
A40  
A130  
A140  
A60  
A50  
P80  
A30  
A10  
A80  
A90  
A20  
P20  
P50  
P75  
P70  
P30  
Amp Kit  
P10  
P90  
P60  
P77  
P100  
P40  
P60  
P120  
P110  
4
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F-20B  
REF NO. PART NO.  
DESCRIPTION  
PRE-MAIN UNIT  
Pre-Main Unit  
Pre-Main Unit  
Pre-Main Unit  
Pre-Main Unit  
REMARKS  
QTY RANK  
F-20B  
J
U,C  
H
B
--  
--  
--  
--  
(V745930)  
(V745940)  
(V745950)  
(V745960)  
P10 V6954800 Chassis  
05  
*
P20 V7460600 Panel Sheet  
P30  
P30  
P30  
P30  
--  
--  
--  
--  
Amp Kit  
Amp Kit  
Amp Kit  
Amp Kit  
J
U,C  
H
(V746070)  
(V746080)  
(V746090)  
(V746100)  
B
P40 V7511400 Spacer Support  
P50 V7017600 Heat Sink  
PINGOOD LCC-10  
2
P60 V7018000 Pan Head Screw  
P70 VB837300 Hexagonal Nut  
P75 VB501900 Spring Washer  
P77 V7834000 Vibration-proof Tape  
P80 V7018100 Pan Head Screw  
P90 V7554300 Button  
4.0X10 MFZN2BL  
#1 4.0 MFZN2Y  
4.0 MFZN2Y  
2
2
2
3.0X10 MFZN2BL  
GA-RED  
2
5
GAIN SELECT  
VOLUME,TREBLRE,HIGH MID  
LOW MID,BASS  
01  
01  
P100 V6955100 Knob  
P110 ET900050 Toothed Lock Washer-B  
4.0 MFZN2BL  
U,C,H,B  
P120  
--  
Earth Mark  
U,C,H,B  
(V777110)  
01  
--  
--  
--  
--  
Amp Kit  
Amp Kit  
Amp Kit  
Amp Kit  
J
U,C  
H
(V746070)  
(V746080)  
(V746090)  
(V746100)  
B
*
*
A10 V7554700 Circuit Board  
A10 V7554800 Circuit Board  
A20 VV849300 Insulation Sheet  
A30 V7356900 Sleeve  
A40 V7054700 Power SW  
A50 XZ805A00 Transformer  
A50 XZ806A00 Transformer  
A50 XZ807A00 Transformer  
A60 VV104600 Cord Holder  
A70 V6286700 Cord  
MAIN  
MAIN  
BFG-20AD 19X24  
12SWS0220  
SDDJE1-A-2  
J
UC  
E
CV-100  
J VCTF  
J,U,C  
H,B  
01  
POWER ON/OFF  
J
U,C  
H,B  
02  
05  
2
01  
04  
J
A70 V6286900 Cord  
A70 V6287000 Cord  
A70 V6287100 Cord  
A80 V7356700 Cord Strain Relief  
A90 V7356800 Cord Strain Relief  
A100 ET800150 Toothed Lock Washer-A  
A110 VL802300 Flat Washer  
A120 LX200060 Hexagonal Nut  
A130 VB508700 Flat Washer  
A140 ES200210 Hexagonal Nut  
UC 3 SJT 18/3  
E 3 HO5VV-F  
UK 3 HO5VV-F  
KR-61 KITAGAWA  
KF-41 KITAGAWA  
9.0 MFZN2Y  
9X14 0.5 FNM3  
9.0 12X2 MFNI33  
18X12.5 0.6 MFZN2  
12.0 14X2 MFNI33  
U,C  
H
B
01  
01  
01  
01  
*New parts  
RANK: Japan only  
5
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F-20B  
ELECTRICAL PARTS  
REF NO. PART NO.  
DESCRIPTION  
REMARKS  
(X0085A0)  
QTY RANK  
ELECTRICAL PARTS  
V7554700 Circuit Board  
V7554800 Circuit Board  
F-20B  
J,U,C  
H,B  
*
*
MAIN  
MAIN  
(X0085A0)  
*
*
V7554700 Circuit Board  
V7554800 Circuit Board  
MAIN  
MAIN  
#18 2P L 60  
B&B #26 5P L 100  
#18 2P L 300  
WH-007  
J,U,C  
H,B  
(X0085A0)  
(X0085A0)  
(V660880)  
(V735970)  
(V744980)  
--  
--  
--  
Connector Assembly  
Connector Assembly  
Connector Assembly  
V6609900 Fuse Holder  
VV291400 Jumper Wire  
0.60  
01  
01  
01  
01  
01  
01  
01  
01  
01  
01  
01  
08  
01  
01  
01  
08  
01  
01  
01  
01  
01  
01  
01  
01  
01  
01  
01  
01  
03  
03  
01  
01  
01  
01  
01  
03  
C01 UR866100 Electrolytic Cap.  
C02 VZ353500 Ceramic Capacitor-SL  
C03 UR847100 Electrolytic Cap.  
C04 VZ353500 Ceramic Capacitor-SL  
C05 VZ353500 Ceramic Capacitor-SL  
C06 UR866330 Electrolytic Cap.  
C07 VV061200 Mylar Capacitor  
C08 UR865470 Electrolytic Cap.  
C09 VV060600 Mylar Capacitor  
C10 UR865100 Electrolytic Cap.  
C11 VV059800 Mylar Capacitor  
C12 VV062600 Mylar Capacitor  
C13 VZ353500 Ceramic Capacitor-SL  
C14 UR866100 Electrolytic Cap.  
C15 VV059800 Mylar Capacitor  
C16 VZ353500 Ceramic Capacitor-SL  
C17 UR866100 Electrolytic Cap.  
C18 FG613100 Ceramic Capacitor-B  
C19 UR866100 Electrolytic Cap.  
C20 UR837470 Electrolytic Cap.  
C21 VV062800 Mylar Capacitor  
C22 VV062800 Mylar Capacitor  
C23 UR847100 Electrolytic Cap.  
-26 UR847100 Electrolytic Cap.  
C27 V7355000 Capacitor  
C28 VZ354600 Monolithic Ceramic Cap.  
C29 VZ354600 Monolithic Ceramic Cap.  
C30 UR749330 Electrolytic Cap.  
C31 UR749330 Electrolytic Cap.  
C32 UR847100 Electrolytic Cap.  
C33 UR847100 Electrolytic Cap.  
CN1 VG879900 Base Post Connector  
CN2 LB932040 Base Post Connector  
CN3 LB918030 Base Post Connector  
DB1 VP344100 Diode Stack  
FZ1 V 7 6 3 0 8 0 Fuse  
1.00 50.0V  
100P 50V J  
10.00 25.0V  
100P 50V J  
100P 50V J  
3.30 50.0V  
6800P 50V J  
0.47 50.0V  
3300P 50V J  
0.10 50.0V  
1000P 50V J  
0.068 50V J  
100P 50V J  
1.00 50.0V  
1000P 50V J  
100P 50V J  
1.00 50.0V  
1000P 50V K  
1.00 50.0V  
47.00 16.0V  
0.1 50V J  
0.1 50V J  
10.00 25.0V  
10.00 25.0V  
4700P 250V J.U.C.S  
0.10 50V Z  
0.10 50V Z  
3300 25.0V  
3300 25.0V  
10.00 25.0V  
10.00 25.0V  
VA- 2P TE  
VH-4P TE  
XH 3P TE  
D2SBA20 1.5A 200V  
315 mA JU  
160 mA E  
J,U,C  
H,B  
FZ1 V 7 8 3 5 7 0 Fuse  
IC1 X0078A00 IC  
-3 X0078A00 IC  
IC4 XZ311A00 IC  
JK1 V3633400 Phone Jack  
JK2 V6176500 Phone Jack  
JK3 V7447000 Phone Jack  
LD1 VV620800 LED  
R01 HF456220 Carbon Resistor  
R02 HF457270 Carbon Resistor  
R03 HF459100 Carbon Resistor  
R04 HF456100 Carbon Resistor  
R05 HF456270 Carbon Resistor  
R06 HF456100 Carbon Resistor  
R07 HF456330 Carbon Resistor  
R08 HF455680 Carbon Resistor  
R09 HF458100 Carbon Resistor  
R10 HF455680 Carbon Resistor  
R11 HF458100 Carbon Resistor  
R12 HF455680 Carbon Resistor  
R13 HF458100 Carbon Resistor  
R14 HF455680 Carbon Resistor  
R15 HF455220 Carbon Resistor  
*New parts  
BA4558  
BA4558  
DIP OPAMP  
DIP OPAMP  
HIFI AMP  
INPUT  
PHONES  
AUX IN  
02  
02  
04  
01  
03  
02  
01  
01  
01  
01  
01  
01  
01  
01  
01  
01  
01  
01  
01  
01  
01  
01  
TDA2030A  
HTJ-064-12I  
HTJ-064-05B  
ST HTJ-035-09ABT  
LT311G-41-C13 RED  
2.2K 1/4 J  
27.0K 1/4 J  
1.0M 1/4 J  
1.0K 1/4 J  
power on/off  
2.7K 1/4 J  
1.0K 1/4 J  
3.3K 1/4 J  
680.0 1/4 J  
100.0K 1/4 J  
680.0 1/4 J  
100.0K 1/4 J  
680.0 1/4 J  
100.0K 1/4 J  
680.0 1/4 J  
220.0 1/4 J  
RANK: Japan only  
6
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F-20B  
REF NO. PART NO.  
DESCRIPTION  
REMARKS  
QTY RANK  
R16 HF456330 Carbon Resistor  
R17 HF457330 Carbon Resistor  
-19 HF457330 Carbon Resistor  
R20 HF458100 Carbon Resistor  
R21 HF457100 Carbon Resistor  
R22 HF457330 Carbon Resistor  
R23 HF456100 Carbon Resistor  
R24 HF457100 Carbon Resistor  
R25 HF457470 Carbon Resistor  
R26 HF455470 Carbon Resistor  
R27 HF457220 Carbon Resistor  
R28 VC740100 Metal Oxide Film Resistor  
R29 VC745000 Metal Oxide Film Resistor  
R30 HF456470 Carbon Resistor  
R31 HF455560 Carbon Resistor  
R32 HF455560 Carbon Resistor  
SW2 VR140800 Push Switch  
3.3K 1/4 J  
33.0K 1/4 J  
33.0K 1/4 J  
100.0K 1/4 J  
10.0K 1/4 J  
33.0K 1/4 J  
1.0K 1/4 J  
10.0K 1/4 J  
47.0K 1/4 J  
470.0 1/4 J  
22.0K 1/4 J  
1.0 1W J  
01  
01  
01  
01  
01  
01  
01  
01  
01  
01  
01  
01  
01  
01  
01  
01  
03  
04  
100.0 1W J  
4.7K 1/4 J  
560.0 1/4 J  
560.0 1/4 J  
VR1 V6607700 Rotary Variable Resistor  
VR2 V7649200 Rotary Variable Resistor  
VR3 V7649200 Rotary Variable Resistor  
VR4 V7649200 Rotary Variable Resistor  
VR5 V7649200 Rotary Variable Resistor  
ZD1 VG440200 Zener Diode  
16mm 25KA  
VOLUME  
TREBLE  
HIGH MID  
LOW MID  
BASS  
*
*
*
*
16mm 10KW(4B)  
16mm 10KW(4B)  
16mm 10KW(4B)  
16mm 10KW(4B)  
MTZ J 12.0B 12.0V  
MTZ J 12.0B 12.0V  
01  
01  
ZD2 VG440200 Zener Diode  
*
XO361A00 Speaker Unit  
4ohm 30W  
V7054700 Power SW  
XZ805A00 Transformer  
XZ806A00 Transformer  
XZ807A00 Transformer  
V6286700 Cord  
SDDJE1-A-2  
J
UC  
E
POWER ON/OFF  
J
U,C  
H,B  
J
02  
05  
J VCTF  
04  
V6286900 Cord  
V6287000 Cord  
V6287100 Cord  
UC 3 SJT 18/3  
E 3 HO5VV-F  
UK 3 HO5VV-F  
U,C  
H
B
*New parts  
RANK: Japan only  
7
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A
B
C
D
E
F
G
H
<P.1>  
OVERALL CIRCUIT DIAGRAM  
F-20B  
D2SBA20 (VP344100)  
DIODE STACK 1.5A 200V  
MAIN 1/2  
1
2
3
4
5
DB1  
GAIN SELECT  
OP AMP  
OP AMP  
OP AMP  
OP AMP  
OP AMP  
AUX IN  
INPUT  
BASS  
LOW MID  
HIGH MID  
TREBLE  
MAIN 2/2  
OP AMP  
OP AMP  
VOLUME  
HIFI AMP  
POWER ON/OFF  
KEC-54238  
OP AMP  
PHONES  
J, U, C  
S, BS  
250V 315mA 250V T160mA L  
4
SPEAKER  
TRANS  
FORMER  
KEC-54238  
WARNING  
Note: See parts list for details of circuit board component parts.  
Components having special characteristics are marked and must be  
replaced with parts having specifications equal to those originally installed.  
F-20B  
F-20B  
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