삼
정
흥
판
Internal Use Only
MICROWAVE OVEN
SERVICE MANUAL
MODEL: MS3447GR
MS3447GRS
CAUTION
BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
July, 2007
Printed in Korea
P/NO : MFL31039007
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CONTENTS
(Page)
SAFETY PRECAUTIONS
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Inside front cover
SPECIFICATIONS
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1-1
2-1
3-1
4-1
CAUTIONS
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INSTALLATION
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OPERATING INSTRUCTIONS
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FEATURES
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4-1
4-1
4-2
4-4
4-5
5-1
CONTROL PANEL
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OPERATING SEQUENCE
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SCHEMATIC DIAGRAM
CIRCUIT DESCRIPTION
SERVICE INFORMATION
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TOOLS AND MEASURING INSTRUMENTS
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5-1
5-1
5-3
5-3
5-7
5-8
MICROWAVE LEAKAGE TEST
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MEASUREMENT OF MICROWAVE POWER OUTPUT
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DISASSEMBLY AND ADJUSTMENT
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INTERLOCK CONTINUITY TEST
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COMPONENT TEST PROCEDURE
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TROUBLE SHOOTING
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5-11
6-1
7-1
EXPLODED VIEW
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REPLACEMENT PARTS LIST
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LGE Internal Use Only
Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
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SPECIFICATIONS
ITEM
MODEL
DESCRIPTION
MS3447GR / MS3447GRS
Power Requiremen
230/240 Volts AC 50 Hz
1600 Watts
Single phase, 3 wire grounded
Power Output
1100 Watts full microwave power (IEC60705)
2450 MHz
Microwave Frequency
Magnetron
2M246-050GF
0 ~ 99 min. 99 sec.
Timer
556mm (W) x 320mm (H) x 438mm (D)
374mm (W) x 254mm (H) x 406mm (D)
16.5 kg (approx.)
Outside Dimensions
Cavity Dimensions
Net Weight
17.9 kg (approx.)
Shipping weight
Control Complement
Touch Control System
Clock : 1:00 - 12:59
Microwave Power for Variable Cooking
Power level
HIGH .................................... Full power throughout the cooking time
...............................
..........
.........
..........
.........
9 (Saute)
approx. 90% of Full power,
approx. 70%,
8 (Reheat)
6 (Medium)
4 (Defrost)
2 (Simmer)
approx. 80%
approx. 60%
approx. 40%
approx. 20%
.......................
........................
7 (Med.-High)
5 (Med.-Low)
approx. 50%,
.................................
3 (Low)
approx. 30%,
..............................
1 (Warm)
approx. 10%
Rating Label Location
Accessories
Owner's manual & cooking guide
Glass turntable
Roller rest
This microwave oven is designed for household use only.
It is not recommended for commercial purposes.
Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
1-1
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CAUTIONS
Unlike other appliances, the microwave oven is
MICROWAVE RADIATION
high-voltage and high-current equipment.
Though it is free from danger in ordinary use,
extreme care should be taken during repair.
Personnel should not be exposed to the
microwave energy which may radiate from the
magnetron or other microwave generating
device if it is improperly used or connection.
All input and output microwave connections,
waveguide, flange, and gasket must be secure
never operate the device without a microwave
energy absorbing load attached.
• DO NOT operate on a 2-wire extension cord during
repair and use.
• NEVER TOUCH any oven components or wiring during
operation.
• BEFORE TOUCHING any parts of the oven, always
remove the power plug from the outlet.
• For about 30 seconds after the oven stops, an electric
charge remains in the high voltage capacitor. When
replacing or checking, you must discharge the high
voltage capacitor by shorting across the two terminals
with an insulated screwdriver.
Never look into an open waveguide or antenna
while the device is energized.
• Proper operation of the microwave oven requires that
the magnetron be assembled to the waveguide and
cavity. Never operate the magnetron unless it is
properly installed.
• Be sure that the magnetron gasket is properly
installed around the dome of the tube whenever
installing the magnetron.
ANTENNA
Gasket
COOLING FIN
FILAMENT
TERMINALS
MAGNETRON
CHASSIS GROUND
MAGNETRON
• Remove your watches whenever working close to or
replacing the Magnetron.
• DO NOT touch any parts of the control panel circuit. A
resulting static electric discharge may damage this
P. C. B.
• NEVER operate the oven with no load.
• NEVER injure the door seal and front plate of the oven
cavity.
THE OVEN IS TO BE SERVICED ONLY
BY PROPERLY QUALIFIED SERVICE
PERSONNEL.
• NEVER put iron tools on the magnetron.
• NEVER put anything into the latch hole and the
interlock switches area.
LGE Internal Use Only
Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
2-1
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INSTALLATION
BEFORE YOU BEGIN, READ THE FOLLOWING INSTRUCTIONS COMPLETELY AND CAREFULLY.
INSTALLING
1. Empty the microwave oven and clean inside it with
a soft, damp cloth. Check for damage such as
misaligned door, damage around the door or dents
inside the cavity or on the exterior.
EARTHING INSTRUCTIONS
This microwave oven is designed to be used in a fully
earthed condition.
It is imperative, therefore, to make sure it is properly
earthed before servicing
2. Put the oven on a counter, table, or shelf that is
strong enough to hold the oven and the food and
utensils you put in it. (The control panel side of the
oven is the heavy side. Use care when handling.)
WARNING-
THIS APPLIANCE
MUST BE EARTHED
3. Do not block the vent and the air intake openings.
Blocking vent or air intake openings can cause
damage to the oven and poor cooking results.
Make sure the microwave oven legs are in place to
ensure proper air flow.
IMPORTANT
The wires in this mains lead are colored in
accordance with the following code:
4. The oven should not be installed in any area where
heat and steam are generated, because they may
damage the electronic or mechanical parts of the
unit.
Green-and-yellow:
Blue:
Brown:
Earth
Neutral
Live
Do not install the oven next to a conventional
surface unit or above a conventional wall oven.
As the colors of the wires in the mains lead of this
appliance may not correspond with the colored
markings identifying the terminals in your plug,
proceed as follows.
5. Use microwave oven in an ambient temperature
less than 104°F(40°C).
6. Place the microwave oven on a sturdy and flat
surface at least 10 cm(4 inches) from the wall.
The wire which is colored green-and-yellow must be
connected to the terminal in the plug which is marked
with the letter E or by the earth symbol ( ) or
colored green or green-and-yellow.
7. Place the microwave oven as far away as possible
from TV, RADIO, COMPUTER, etc., to prevent
interference.
The wire which is colored blue must be connected to
the terminal in the plug which is marked with the letter
N or colored black.
10cm
The wire which is colored brown must be connected
to the terminal in the plug which is marked with the
letter L or colored red.
Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
3-1
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OPERATING INSTRUCTIONS
FEATURES
CONTROL PANEL
1. SENSOR REHEAT.
2. SENSOR COOK.
3. AUTO COOK: Used to select the auto cook
4. AUTO REHEAT: Used to select the auto reheat.
1
2
5. AUTO DEFROST: This feature provides you with the best
defrosting method for frozen foods.
6. MORE / LESS: All of the one touch cook and TIMED COOK
can be adjusted to cook food for a longer or shorter time.
MORE
Pressing MORE will add 10 seconds to the
cooking time.
3
5
4
LESS
Pressing LESS will subtract 10 seconds of
cooking time.
7. QUICK-DEFROST: You can thaw specific foods and
weight very quickly.
6
7
8. NUMBER: These used to set for time of day, cooking time,
power level, or defrost weight.
9. CLOCK: It is used to set the time of day.
8
10. POWER: You can select power level for cooking.
11. STOP/CLEAR: It used to stop oven and clear all entries
except time of day.
10
12
9
12. START/Q-START: To quickly set the cooking time
directly.
11
LGE Internal Use Only
Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
4-1
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OPERATING SEQUENCE
The following is a description of component functions
during oven operation.
6. CHILD LOCK
This oven has a CHILD LOCK feature
TO SET CHILD LOCK
1. CANCEL FUNCTION
• Touch STOP/CLEAR pad
• Touch and hold STOP/CLEAR pad
appears on the display.
Touch the STOP/CLEAR pad whenever you need to
cancel an entry or a function currently in use.
The display will return either to the last item entered
or to the clock.
LOCKED
LOCKED
TO CANCEL CHILD LOCK
• Touch and hold STOP/CLEAR pad
disappears.
2. AUTO TOUCH
STOP/CLEAR
POPCORN
NUMBER OF TABLE
7. MORE / LESS
NOTE: • Heat only 1 package at a time
• Then the oven will start automatically.
The cook time is adjustable by MORE pad or LESS
pad
STOP/CLEAR
COOKING
MORE/LESS
3. TIME COOKING
STOP/CLEAR
TIME
NUMBER
START
POWER
8. AUTO REHEAT
NUMBER
AUTO
REHEAT
STOP/CLEAR
NUMBER OF TABLE
4. MULTI-STAGE COOKING
NOTE: Then the oven will start automatically.
You can program your oven to switch from one power
level to another for up to 3 stages.
To set a 2-stage cook cycle.
9. Q UICK DEFROST
■ 1ST STAGE
STOP/CLEAR
QUICK DEFROST
STOP/CLEAR
TIME
NUMBER
POWER
NUMBER
10. AUTO COOK
■ 2ND STAGE
STOP/CLEAR
AUTO COOK
NUMBER OF TABLE
TIME
NUMBER
START
POWER
NOTE: Then the oven will start automatically.
NUMBER
5. AUTO DEFROST COOKING
AUTO
DEFROST
STOP/CLEAR
NUMBER
NUMBER OF
WEIGHT
START
Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
4-2
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SCHEMATIC DIAGRAM
LGE Internal Use Only
Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
4-3
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CIRCUIT DESCRIPTION
• A high voltage of approximately 2100 volts AC is
generated in the secondary of the high voltage
transformer which is increased by the action of the high
voltage diode and charging of the high voltage
capacitor.
GENERAL DETAILS
• The low voltage transformer supplies the necessary
voltage to the micom controller when power cord is
plugged in.
• When the door is closed, the primary switch is ON, the
secondary switch is ON, and the monitor switch opens
(contact COM and NO).
• The negative 4000 Volts DC is applied to the filament
of the magnetron.
WHEN THE OVEN IS SET AT ANY LEVEL
EXCEPT MAXIMUM.
• The micom controller controls the ON-OFF time of
relay 2 by the applied signal to vary the average output
power of microwave oven as POWER LEVEL.
(refer to page 1-1)
WHEN SELECTING COOKING POWER
LEVEL AND TIME
• The micom controller memorizes the function you set.
• The time you set appears in the display window.
• Each indicator light turns on to indicate that the stage
has been set.
• One complete cycle of relay 2 is 22 seconds.
WHEN TOUCHING THE START PAD
• The coil of the relay is energized by the micom
controller.
• Power input is supplied to the high voltage transformer
through the fuse to the primary switch and relay 2.
• Turntable rotates.
WHEN THE DOOR IS OPENED DURING
COOKING
• Both the primary switch and relay 2 cut off the primary
winding voltage of the high voltage transformer.
• ON-OFF of relay 2 is coupled electrically with opening
and closing of the secondary switch.
• When the door is opened, the secondary switch is
opened and when the door is closed, the secondary
switch is closed.
PRIMARY
SWITCH
FUSE
• The cooking time stops counting down.
• Relay stops functioning.
L
H.V.
TRANS-
FORMER
• As the door is opened, if the contact of primary switch
and relay 2 and/or secondary switch fail to open, the
fuse opens due to the large current surge caused by
the monitor switch activation, which in turn stops
magnetron oscillation.
MONITOR
SWITCH
N
SECONDARY
SWITCH
PRIMARY
SWITCH
FUSE
RELAY 2
MICOM CONTROLLER
L
H.V.
MONITOR
TRANS-
• The fan motor rotates and cools the magnetron by
blowing the air (coming from the intake on the base-
plate).
SWITCH
FORMER
N
• The air is also directed into the oven to exhaust the
vapor in the oven through the upper plate.
• Cooking time starts counting down.
SECONDARY
SWITCH
RELAY 2
• 3.3 volts AC is generated from the filament winding of
the high voltage transformer. This 3.3 volts is applied to
the magnetron to heat the magnetron filament through
two noise-preventing choke coils.
MICOM CONTROLLER
Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
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SERVICE INFORMATION
TOOLS AND MEASURING INSTRUMENTS
NECESSARY TOOLS
NECESSARY MEASURING INSTRUMENTS
Tools normally used for TV servicing are sufficient.
Standard tools are listed below.
• Diagonal pliers
• TESTER (VOLTS-DC, AC, Ohmmeter)
• Microwave survey meter
- Holaday HI-1500
HI-1501
• Long nose pliers
• Phillips screwdriver
• Flat blade screwdriver
• Wrench (size 5mm)
• Nutdriver (size 5mm)
• Adjustable wrench
- Narda 8100
8200
• Inch scale
• 600 cc non conductive material beaker (glass or plastic),
inside diameter: approx. 8.5 cm (3 / in.)
1
2
• Soldering iron
• Solder
• Vinyl insulation tape
• Polishing cloth
• Cylindrical and made of borosilicate glass vessel.
max. thickness: 3 mm
outside diameter: approx. 190mm
height: approx. 90mm
• Glass thermometer: 100°C or 212°F (1 deg scale)
MICROWAVE LEAKAGE TEST
CAUTIONS
• Be sure to check microwave leakage prior to
servicing the oven if the oven is operative prior to
servicing.
• The service personnel should inform the
manufacture importer, or assembler of any certified
oven unit found to have a microwave emission
MEASURING MICROWAVE ENERGY
LEAKAGE
• Pour 275 15cc of 20 5°C(68 9°F) water in a beaker
which is graduated to 600 cc, and place the beaker
on the center of the turntable.
• Set the energy leakage monitor to 2,450 MHz and
use it following the manufacturer's recommended
test procedure to assure correct result.
• When measuring the leakage, always use the 2- inch
(5cm) spacer supplied with the probe.
• Operate the oven at its maximum output.
• Measure the microwave radiation using and
electromagnetic radiation monitor by holding the
probe perpendicular to the surface being measured
2
level in excess of 5 mW/cm and should repair any
unit found to have excessive emission levels at no cost
to the owner and should ascertain the cause of the
excessive leakage. The service personnel should
instruct the owner not to use the unit until the oven has
been brought into compliance.
• If the oven operates with the door open, the service
personnel should:
- Tell the user not to operate the oven.
- Contact the manufacturer.
Move probe along shaded area
• The service personnel should check all surface and
vent openings for microwave leakage.
Probe scanning speed
Less than 2.5 cm/sec
(1 in/sec)
• Check for microwave leakage after every servicing. The
power density of the microwave radiation leakage
emitted by the microwave oven should not exceed
4 mW/cm2. Always start measuring of an unknown field
to assure safety for operating personnel from radiation
leakage.
LGE Internal Use Only
Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
5-1
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MEASUREMENT WITH OUTER CASE
REMOVED
• When you replace the magnetron, measure for
microwave energy leakage before the outer case is
installed and after all necessary components are
replaced or adjusted.
Special care should be taken in measuring the
following parts. (Circled area of Fig. below)
- Around the magnetron
NOTES WHEN MEASURING
• Do not exceed meter full scale deflection.
• The test probe must be moved no faster than
1 inch/sec (2.5 cm/sec) along the shaded area,
otherwise a false reading may result.
• The test probe must be held by the grip portion of the
handle.
A false reading may result if the operator's hand is
between the handle and the probe.
• When testing near a corner of the door, keep the probe
perpendicular to the surface making sure the probe
horizontally along the oven surface. Hold vertically
when testing the top and bottom, and horizontally
along.
- The waveguide
WARNING : AVOID CONTACTING ANY
HIGH VOLTAGE PARTS
RECORD KEEPING AND NOTIFICATION
AFTER MEASUREMENT
• After adjustment and repair of any microwave energy
interruption or microwave energy blocking device,
record the measured values for future reference. Also
enter the information on the service invoice.
• The microwave energy leakage should not be more
than 4 mW/cm.sq. after determining that all parts are in
good condition, functioning properly and genuine
replacement parts which are listed in this manual have
been used.
• At least once a year, have the electromagnetic energy
leakage monitor checked for calibration by its
manufacturer.
MEASUREMENT WITH A FULLY
ASSEMBLED OVEN
• After all components, including the outer case, are fully
assembled, measure for microwave energy leakage
around the door viewing window, the exhaust opening,
and air inlet openings.
• Microwave energy leakage must not exceed the values
prescribed below.
NOTE: Leakage with the outer case removed less than
5 mW/cm.sq. Leakage for a fully assembled
oven (Before the latch switch (primary) is
interrupted) with the door in a slightly opened
position-less than 2 mW/cm.sq.
Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
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MEASUREMENT OF MICROWAVE POWER OUTPUT
• Microwave power output measurement is made with
the microwave oven supplied at its rated voltage and
operated at its maximum microwave power setting with
a load of (1000 5) g of potable water.
• The water is contained in a cylindrical borosilicate glass
vessel having a maximum material thickness of 3 mm
and an outside diameter of approximately 190mm.
• The oven and the empty vessel are at ambient
temperature prior to the start of the test.
• The initial temperature (T1) of the water is (10 2)°C. It
is measured immediately before the water is added to
the vessel. After addition of the water to the vessel,
the load is immediately placed on the center of the
turntable which is in thd lowest position and the
microwave power switched on.
• The time T for the temperature of the water to rise by a
value ∆ T of (10 2)°K is measured, where T is the time
in seconds and ∆T is the temperature rise. The initial
and final water temperatures are selected so that the
maximum difference between the final water
• The microwave power output P in watts is calculated
from the following formula :
4187 x (∆T) + 0.55 X (T2 - T0 ) X M
P =
T
• T2: Temperature after heating
• T0: Temperature of bowl
• M: Weight of bowl
is measured while the microwave generator is
operating at full power. Magnetron filament heat-up
time is not included. (about 3 sec)
• The water is stirred to equalize temperature throughout
the vessel, prior to measuring the final water
temperature.
• Stirring devices and measuring instruments are
selected in order to minimize addition or removal of
heat.
temperature and the ambient temperature is 5°K.
DISASSEMBLY AND ADJUSTMENT
Remove the screw
A. OUTER CASE REMOVAL
1) Disconnect the power supply cord from the outlet.
2) Remove the screws from the rear of the case.
The outer case must be moved backward to be lifted
off.
B. POWER SUPPLY CORD
1) Remove the outer case.
2) Disconnect two terminals and remove one screw of the
ground terminal.
C. CONTROL PANEL ASSEMBLY
1) Open the door.
2) Disconnect the lead wire from RELAY (RY2) of the
PCB SUB ASSEMBLY.
Lift up and pull out control panel
3) Disconnect the leadwire from connector (CN1) of the
PCB SUB ASSEMBLY.
4) Remove screw which hold the controller assembly to the
cavity.
5) Lift up and pull out control panel assembly carefully
from the cavity.
CAUTION: DISCHARGE THE HIGH VOLTAGE
CAPACITOR BEFORE SERVICING
(refer to page 2-1)
LGE Internal Use Only
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Remove choke cover
D. PCB ASSEMBLY REMOVAL
1) Remove the control panel assembly from the
cavity. (Refer to control panel assembly removal
on previous page.)
2) Remove screws which hold the PCB SUB ASS ’Y to
the control panel.
3) Disconnect the flat cable from the PCB SUB
ASS’Y and take off the PCB SUB ASS ’Y
Remove door assembly
E. DOOR MAIN ASSEMBLY REMOVAL
1) Open the door.
2) Remove the choke cover very carefully with a flat-blade
screwdriver.
CAUTION: Be careful not to damage door seal plate
by screwdriver.
3) Lift up and push the door.
NOTE:
1. After replacing the door, be sure to check that the
primary switch, monitor switch, and secondary switch
operate normally.
Spacer
2. After replacing the door, check for microwave energy
leakage with a survey meter. Microwave energy must
be below the limit of 4 mW/cm2. (with a 275 ml water
load)
3. When mounting the door assembly to the oven
assembly, be sure to adjust the door assembly parallel
to the chassis. Also adjust so the door has no play
between the inner door surface and oven frame
assembly. If the door assembly is not mounted
properly, microwaves may leak from the clearance
between the door and the oven.
Copyright © 2007 LG Electronics. Inc. All right reserved.
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LGE Internal Use Only
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F. AIR DUCT ASSEMBLY REMOVAL
H. REMOVING THE TURNTABLE MOTOR
1) Disconnect the leadwire from the lamp.
2) Remove the mounting screw to the magnetron.
1) Remove the turntable and rotating ring.
2) Lay the unit down on its back.
3) Remove the turntable motor cover.
The turntable base cover is easily removed by
pinching the eight parts with a wire cutting.
4) Disconnect the leadwire from the turntable motor
terminals.
5) Remove the screw securing the turntable motor to
the oven cavity ASS’Y.
6) After repairing the motor, rotate the removed
turntable motor cover.
7) Fit the turntable motor cover’s projecting part to the
base plate slit.
8) The taptite screw shall be used when a turntable
motor cover is secured with a screw.
G. MAGNETRON REMOVAL
1) Disconnect the lead wire from the magnetron.
2) Carefully remove the mounting screws holding the
magnetron and the waveguide.
3) Remove the magnetron ASS’Y until the tube is
clear from the waveguide.
NOTE:
1. When removing the magnetron, make sure its
dome does not hit any adjacent parts, or it may be
damaged.
2. When replacing the magnetron, be sure to install
the magnetron gasket in the correct position and
be sure that the gasket is in good condition.
3. After replacing the magnetron, check for microwave
leakage with a survey meter around the
magnetron. Microwave energy must be below the
limit of 5 mW/cm2. (With a 275 ml. water load).
Make sure that gasket is rigidly attached to the
magnetron. To prevent microwave leakage,
tighten the mounting screws properly, making sure
there is no gap between the waveguide and the
magnetron.
NOTE:
1. Remove the wire lead from the turntable motor
VERY CAREFULLY.
2. Be sure to grasp the connector, not the wires, when
removing.
Air duct
Magnetron
Waveguide
Dome
Taptite Screw
Waveguide
Bracket
Magnetron
Gasket
Wire Leads
Magnetron
Turntable Motor
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I. HIGH VOLTAGE TRANSFORMER
REMOVAL
1) Discharge the high voltage capacitor.
2) Disconnect the lead wire from magnetron, high voltage
transformer, and capacitor.
L. INTERLOCK SYSTEM
1) INTERLOCK MECHANISM
The door lock mechanism is a device which has
been specially designed to eliminate completely
microwave activity when the door is opened during
cooking and thus to prevent the danger resulting
from the microwave leakage.
3) Remove the screw holding the high voltage
transformer to the baseplate.
J. FAN MOTOR ASSEMBLY REMOVAL
1) Discharge the high voltage capacitor.
2) Disconnect the lead wire from fan motor and high
voltage capacitor.
ADJUSTMENT
DIRECTION
3) Remove the two screws holding the the suction guide
ASS’Y to the oven cavity and remove the high voltage
diode earth screw.
SECONDARY
SWITCH
4) Remove the two screws holding the fan motor ASS’Y
to the suction guide ASS’Y.
MONITOR
SWITCH
K. HIGH VOLTAGE CAPACITOR AND
DIODE REMOVAL
PRIMARY
SWITCH
1) Discharge the high voltage capacitor.
2) Disconnect the lead wire from fan motor and high
voltage capacitor.
3) Remove the screw holding the suction guide ASS’Y to
the oven cavity and remove the high voltage diode
earth screw.
4) Remove the screw holding the high voltage capacitor
bracket.
2) MOUNTING OF THE PRIMARY/MONITOR/
SECONDARY SWITCHES TO THE LATCH
BOARD
3) INSTALLATION AND ADJUSTMENT OF THE
LATCH BOARD TO THE OVEN ASSEMBLY
• Mount the latch board to the oven assembly.
• Adjust the latch board in the arrow direction so that
oven door will not have any play in it when the door
is closed.
Fan Motor
ASS’Y
• Tighten the mounting screw.
Suction
Guide
• Check for play in the door by pushing the door
release button. Door movement should be less
than 0.5 mm. (1/64 inch)
Don't push the door release button while making this
adjustment. Make sure that the latch moves
smoothly after adjustment is completed and that the
screws are tight. Make sure the primary, monitor,
and secondary switches operate properly by
following the continuity test procedure.
H.V.
Transformer
H.V.
Capacitor
H.V.
Diode
Copyright © 2007 LG Electronics. Inc. All right reserved.
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LGE Internal Use Only
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INTERLOCK CONTINUITY TEST
WARNING : FOR CONTINUED PROTECTION AGAINST EXCESSIVE RADIATION
EMISSION, REPLACE ONLY WITH IDENTICAL REPLACEMENT PARTS.
TYPE NO.SZM-V 16-FA-63 OR VP-533A-OF FOR PRIMARY SWITCH
TYPE NO.SZM-V 16-FA-62 OR VP-532A-OF FOR MONITOR SWITCH
TYPE NO.SZM-V 16-FA-63 OR VP-533A-OF FOR SECONDARY SWITCH
A. PRIMARY INTERLOCK SWITCH TEST
B. SECONDARY INTERLOCK SWITCH TEST
When the door release button is depressed slowly
with the door closed, an audible click should be
heard at the same time or successively at
intervals. When the button is released slowly, the
latches should activate the switches with an
audible click.
If the latches do not activate the switches when
the door is closed, the switches should be a
adjusted in accordance with the adjustment
procedure. Disconnect the wire lead from the
primary switch. Connect the ohmmeter leads to
the common (COM) and normally open (NO)
terminal of the switch. The meter should indicate
an open circuit in the door open condition.
When the door is closed, the meter should
indicate a closed circuit.
Disconnect the wire lead from the secondary
switch.
Connect the ohmmeter leads to the common
(COM) and normally open (NO) terminals of the
switch. The meter should indicate a open circuit in
the door open condition. When the door is closed,
meter should indicate an closed circuit. When the
secondary switch operation is abnormal, make the
necessary adjustment or replace the switch only
with the same type of switch.
C. MONITOR SWITCH TEST
Disconnect the wire lead from the monitor switch.
Connect the ohmmeter leads to the common
(COM) and normally closed (NC) terminals of the
switch. The meter should indicate closed circuit in
the door open condition. When the door is closed,
meter should indicate an open circuit. When the
monitor switch operation is abnormal, replace with
the same type of switch.
When the primary switch operation is abnormal,
make the necessary adjustment or replace the
switch only with the same type of switch.
NOTE: After repairing the door or the interlock
system, it is necessary to do this continuity
test before operating the oven.
COMPONENTS
TEST PROCEDURE
RESULTS
SWITCHES
(Wire leads removed)
Check for continuity of the
switch with an Ohm-meter
Door
open
Door
closed
Primary
NO
COM
Switch
NC
Monitor
COM
Switch
Secondary
NO
COM
Switch
NOTE : After checking for the continuity of switches, make sure that they are
connected correctly.
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COMPONENT TEST PROCEDURE
CAUTIONS
1. DISCONNECT THE POWER SUPPLY CORD FROM THE OUTLET WHENEVER REMOVING THE
OUTER CASE FROM THE UNIT. PROCEED WITH THE TEST ONLY AFTER DISCHARGING THE HIGH
VOLTAGE CAPACITOR AND REMOVING THE WIRE LEADS FROM THE PRIMARY WINDING OF THE
HIGH VOLTAGE TRANSFORMER. (SEE PAGE 2-1)
2. ALL OPERATIONAL CHECKS WITH MICROWAVE ENERGY MUST BE DONE WITH A LOAD (1 LITER
OF WATER IN CONTAINER) IN THE OVEN.
COMPONENTS
TEST PROCEDURE
RESULTS
HIGH VOLTAGE
TRANSFORMER
(Wire leads removed)
FILAMENT
WINDING
PRIMARY
TERMINAL
1. Measure the resistance.
(Ohm-meter scale: Rx1 and Rx100)
• Primary winding
• Secondary winding
Approx.: 0.2 ~ 0.4 ohm
Approx.: 70 ~100 ohm
Less than: 1 ohm
• Filament winding
2. Measure the resistance.
(Ohm-meter scale: Rx1000)
• Primary winding to ground
• Filament winding to ground
Normal: Infinite
Normal: Infinite
MAGNETRON
(Wire leads removed)
1. Measure the resistance.
(Ohm-meter scale: Rx1)
• Filament terminal
Normal: Less than 1 ohm
Normal: Infinite
2. Measure the resistance.
(Ohm-meter scale: Rx1000)
• Filament to chassis
Copyright © 2007 LG Electronics. Inc. All right reserved.
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COMPONENTS
TEST PROCEDURE
RESULTS
Antenna
Gasket
Chassis
Filament
NOTE: When testing the magnetron, be sure to install the magnetron gasket
in the correct position and be sure that the gasket is in good condition.
HIGH VOLTAGE
CAPACITOR
Measure the resistance.
(Ohm-meter scale: Rx1000)
• Terminal to terminal.
Normal: Momentarily indicates
several ohms, and
then gradually returns
to infinite.
Normal: Infinite.
Measure the resistance.
(Ohm-meter scale: Rx1000)
• Terminal to case.
Measure the continuity (Forward).
(Ohm-meter scale: Rx10000)
HIGH VOLTAGE
DIODE
Normal: Continuity.
Abnormal: Infinite.
NOTE :
Some inexpensive meters
may indicate infinite
resistance in both direction.
Normal: Infinite.
Abnormal: Continuity.
Measure the continuity (Reverse).
(Ohm-meter scale: Rx10000)
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COMPONENTS
TEST PROCEDURE
RESULTS
RELAY 2
Check for continuity of relay 2 with an
ohm-meter.
(Remove wire leads from relay 2 and
operate the unit.)
POWER
LEVEL
1
2
4 sec
6 sec
8 sec
10 sec
12 sec
14 sec
16 sec
18 sec
20 sec
22 sec
18 sec
16 sec
14 sec
12 sec
10 sec
8 sec
6 sec
4 sec
2 sec
0 sec
3
4
5
6
7
8
9
10
Relay 2
Measure the resistance.
(Ohm-meter scale: R x 1)
Normal:
A: Approx. 85 ~ 100 ohm
B: Approx. 10 ~ 25 ohm
FAN MOTOR
(Wire leads removed)
Abnormal: Infinite or several
ohm.
B
A
Normal: Approx. 100~150 ohm
Measure the resistance.
(Ohm-meter scale: R x 1)
TURNTABLE
MOTOR
Abnormal: Infinite or several
ohm.
(Wire leads removed)
NOTE : • A MICROWAVE LEAKAGE TEST MUST ALWAYS BE PERFORMED WHEN THE UNIT IS
SERVICED FOR ANY REASON.
• MAKE SURE THE WIRE LEADS ARE IN THE CORRECT POSITION.
• WHEN REMOVING THE WIRE LEADS FROM THE PARTS, BE SURE TO GRASP THE
CONNECTOR, NOT THE WIRES.
Copyright © 2007 LG Electronics. Inc. All right reserved.
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LGE Internal Use Only
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TROUBLE SHOOTING
WHEN YOU GET A COMPLAINT FROM YOUR CUSTOMER, EVALUATE THE COMPLAINT CAREFULLY. IF
THE FOLLOWING SYMPTOMS APPLY, PLEASE INSTRUCT THE CUSTOMER IN THE PROPER USE OF THE
MICROWAVE OVEN. THIS CAN ELIMINATE AN UNNECESSARY SERVICE CALL.
CAUTIONS
1. Check grounding before checking for trouble.
2. Be careful of the high voltage circuit.
3. Discharge the high voltage capacitor. (See page 2-1)
4. When checking the continuity of the switches or of the high voltage transformer, disconnect one lead wire
from these parts and then check continuity with the AC plug removed. To do otherwise may result in a
false reading or damage to your meter.
5. Do not touch any part of the circuit on the PCB since static electric discharge may damage this control
panel.
Always touch yourself to ground while working on this panel to discharge any static charge built up in your
body. (Micom model only)
CONDITION
CAUSE
REMEDY
Microwave oven
does not work.
Avoid using other electrical
appliances when you use the
microwave oven.
Inserting many plugs into one
outlet and using them at the
same time
(blown fuse or breaker)
Microwave oven plug is not
inserted tightly.
Insert microwave oven plug
securely.
Use the microwave oven at
adequate line voltage.
Output power is too low.
Low AC input voltage.
This may not be a defect.
It is possible that the food
should be cooked for a
longer time period.
Food temperature is too low.
Using metallic ware and
allowing it to touch the oven
wall.
Do not use metallic ware for
cooking except that noted in
the cooking guide.
Sparks occur.
Do not use any type of
cookware with metallic
trimming.
Ceramic ware trimmed in
gold or silver powder is used.
1. Use plastic wrap or lid.
2. Stir once or twice while
cooking soup, cocoa or
milk, etc.
Inconsistent intensity of
microwave by their
characteristics.
Uneven cooking.
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(TROUBLE 1) The following visual conditions indicate a probable defective control circuit.
1. Incomplete segments.
• Segment missing.
• Partial segment missing.
• Digit flickering (NOTE: Slight flickering is normal.)
2. Colon does not turn on or blink.
3. A distinct change in the brightness of one or more numbers in display.
4. One or more digits in the display are not lighting.
5. Display indicates a number different from one touched, for example, key in 5 and 3 appears in the display.
6. Specific numbers (for example 7 or 9) will not display when key pad is touched.
7. Display does not count down with time blinking or up with clock operation.
8. Display obviously jumps in time while counting down.
9. Display counts down too fast while cooking.
10. Each indicator light does not turn on after setting cooking cycle.
11. Display time of day does not reappear when cooking is finished.
CONDITION
CHECK
RESULT
CAUSE
REMEDY
1. No input can be
programmed.
Defective PCB
assembly.
Replace PCB
assembly.
Check the conn-
ection between
membrane key
assembly and
PCB assembly.
Continuity.
Loose
connection.
Connect them
tightly.
No continuity.
Everything works
as specified.
2. Some inputs
cannot be
programmed.
Defective key
membrane
assembly.
Replace key
membrane
assembly.
Replace key
membrane
assembly and
check operation.
Defective PCB
assembly.
Replace PCB
assembly.
3. Display shows a
number or figure
different from one
touched.
Still have trouble.
4. Random
programming
when touching
other pads.
5. Display is fixed
at some figure
and can not
accept any
input.
Copyright © 2007 LG Electronics. Inc. All right reserved.
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(TROUBLE 2) Oven does not operate at all, Display window does not display any figures,
and no input is accepted.
CONDITION
CHECK
RESULT
CAUSE
REMEDY
Malfunction of the
monitor switch.
Replace fuse,
primary, monitor,
secondary
switches, and
RELAY(RY2) of
P.C.B Assembly.
Check continuity
of monitor
switch (with
door closed).
1. Fuse blows.
Continuity.
No continuity.
Replace fuse
Replace fuse,
primary, monitor,
secondary
Check continuity
of primary
switch (with
Continuity.
Shorted contact at
the primary switch.
switches, and
RELAY(RY2) of
P.C.B Assembly.
door opened).
No continuity.
Replace fuse,
primary, monitor,
secondary
Check continuity
of secondary
switch (with
Continuity.
Malfunction of
secondary switch.
switches, and
RELAY(RY2) of
P.C.B Assembly.
door opened).
No continuity.
Defective high
voltage capacitor.
Replace high
voltage capacitor.
Disconnect one
side of the wire
lead connected
from transformer
to the high
Normal.
Defective high volt-
age transformer.
Replace high volt-
age transformer.
Fuse blows again
voltage
capacitor and
operate the unit.
NOTE : All these switches must be replaced at the same time. Refer to page 5-7, 5-8
2. Fuse does not
blow.
Defective
thermostat.
Replace
thermostat.
No continuity.
Continuity.
Check continuity
of thermostat.
Check continuity
of power supply
cord.
No continuity.
5-13
Defective power
supply cord.
Replace power
supply cord.
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(TROUBLE 3) Display shows all figures set, but oven does not start cooking while desired
program times are set and START pad is touched.
CONDITION
CHECK
RESULT
No continuity.
Continuity.
CAUSE
REMEDY
Defective
secondary switch.
Replace
secondary switch.
Check continuity
of secondary
switch (with
1.Setting time
does not count
down when
touching START
pad.
door closed).
Replace PCB
assembly.
Defective PCB
assembly.
Check the con-
nection between
CN1 connector
and PCB
Continuity
Connect them
tightly.
Loose connection.
No continuity
assembly.
2. Fan motor or
oven lamp do
not turn on.
Defective fan motor.
Defective oven lamp.
Replace fan motor.
Replace oven lamp.
Check fan motor.
Check oven lamp.
Abnormal.
Abnormal.
Normal.
(TROUBLE 4) Oven seems to be operating but little heat is produced in oven load.
CONDITION
CHECK
RESULT
CAUSE
REMEDY
Suggest customer
contact local
electric power
utility co. or
qualified
Lower than 90% of
rating voltage.
Check the
power source
voltage.
Decrease in power
source voltage
with load.
Output is low.
Normal.
electrician.
Disconnect the
wire leads from
relay 2 and
check on and off
time with
Defective PCB
assembly.
Replace PCB
assembly.
Abnormal.
Normal.
multitester.
Measure the
output power.
Defective
magnetron.
Replace
magnetron.
Abnormal.
NOTE: Simple test of power output-conducted by heating one liter water for one min. if available.
Minimum 8.5˚C temperature rise is normal condition.
Copyright © 2007 LG Electronics. Inc. All right reserved.
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(TROUBLE 5) No microwave oscillation even though oven lamp and fan motor run.
(Display operates properly)
CONDITION
CHECK
RESULT
No continuity.
Continuity.
CAUSE
REMEDY
Defective PCB
assembly
No microwave
oscillation.
Replace PCB
assembly
Disconnect the
wire leads from
relay 2 and
check continuity
of relay 2.
(Operate the unit)
Defective high
voltage
transformer.
Replace high
voltage
transformer.
Check high vol-
tage transformer
Abnormal
Normal
Check high vol-
tage capacitor
Defective high
voltage capacitor.
Replace high
voltage capacitor.
Abnormal
Normal
Check high vol-
tage diode
Defective high
voltage diode.
Replace high
voltage diode.
Abnormal
Normal
Check
magnetron.
Defective
magnetron.
Replace
magnetron.
Abnormal
NOTE : • Make sure the wire leads correct position.
• When Removing the wire leads from the parts, be sure to grasp the connector, not the wires.
• When removing the magnetron, be sure to install the magnetron gasket in the correct position
and in good condition.
Defective PCB
assembly.
Replace PCB
assembly.
Output is full power
when you set lower
power level.
Disconnect the
Abnormal.
wire leads from
relay 2 and check
continuity relay 2.
(Operate the unit)
LGE Internal Use Only
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5-15
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#EV#
EXPLODED VIEW
INTRODUCTION
MODEL: MS3447GR
MS3447GRS
OVEN CAVITY PARTS
INTERIOR PARTS
BASE PLATE PARTS
LATCH BOARD PARTS
DOOR PARTS
CONTROL PANEL PARTS
-6-1-
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#EV#
DOOR PARTS
15006A
13581A
13552A
13536A
13213A
14890A
13720D
14026A
14970A
-6-2-
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#EV#
CONTROL PANEL PARTS
24781M
23790D
23572A
268711
WTP018
23506A
24510L
24970A
250201
-6-3-
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#EV#
OVEN CAVITY PARTS
WTT021
33112U
33052A
WTT010
33390G
36549S
35889A
WTP013
-6-4-
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#EV#
LARCH BOARD PARTS
WSZ085
466001
43501A
43500A
466003
466001
-6-5-
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#EV#
INTERIOR PARTS
568771
WSZ062
56411A
WTT021
WTP004
56501A
54974T
50FZZA
56201A
56930V
34930W
56549F
WTT028
WEB001
54974S
55900A
WTT037
WSZ
002
WTT028
50CZZH
54810C
35012A
WSZ002
56912B
WSZ002
56324A
WTT028
WSZ002
948501
55262A
56851D
948502
56901A
56201B
-6-6-
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#EV#
BASE PLATE PARTS
56170D
63302A
63303A
948502
65006B
WSZ002
WTT021
-6-7-
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