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MICROWAVE OVEN
SERVICE MANUAL
MODEL: MS3046SQ
CAUTION
BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
June, 2009
P/NO : MFL38934612 Printed in Korea
SAFETY PRECAUTIONS
This device is to be serviced only by properly qualified service personnel.
Consult the service manual for proper service procedures to assure continued safety operation and for precautions to be
taken to avoid possible exposure to excessive microwave energy.
PRECAUTIONS TO BE OBSERVED BEFORE AND
DURING SERVICING TO AVOID POSSIBLE
EXPOSURE TO EXCESSIVE MICROWAVE ENERGY
A) Do not operate or allow the oven to be operated with the door open.
B) Make the following safety checks on all ovens to be serviced before activating the magnetron or other
microwave source, and make repairs as necessary; (1) interlock operation, (2) proper door closing, (3)
seal and sealing surfaces (arcing, wear, and other damage), (4) damage to or loosening of hinges and
latches, (5) evidence of dropping or abuse.
C) Before turning on microwave power for any service test or inspection within the microwave generating
compartments, check the magnetron, wave guide or transmission line, and cavity for proper alignment,
integrity, and connections.
D) Any defective or misadjusted components in the interlock, monitor, door seal, and microwave generation
and transmission systems shall be repaired, replaced, or adjusted by procedures described in this manual
before the oven is released to the owner.
E) A microwave leakage check to verify compliance with the Federal Performance Standard should be
performed on each oven prior to release to the owner.
CAUTION
MICROWAVE RADIATION
DO NOT BECOME EXPOSED TO RADIATION FROM THE MICROWAVE GENERATOR
OR OTHER PARTS CONDUCTING MICROWAVE ENERGY.
Copyright © 2007 LG Electronics. Inc. All right reserved. LGE Internal Use Only
Only for training and service purposes
CONTENTS
(Page)
SAFETY PRECAUTIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Inside front cover
SPECIFICATIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1-1
CAUTIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2-1
INSTALLATIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3-1
OPERATING INSTRUCTIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4-1
FEATURES - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4-1
CONTROL PANEL - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4-1
OPERATING SEQUENCE - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4-2
SCHEMATIC DIAGRAM - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4-3
CIRCUIT DESCRIPTION - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4-4
SERVICE INFORMATION - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5-1
TOOLS AND MEASURING INSTRUMENTS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5-1
MICROWAVE LEAKAGE TEST - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5-1
MEASUREMENT OF MICROWAVE POWER OUTPUT - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5-3
DISASSEMBLY AND ADJUSTMENT - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5-3
INTERLOCK CONTINUITY TEST - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5-7
COMPONENT TEST PROCEDURE - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5-8
TROUBLE SHOOTING - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5-11
EXPLODED VIEW - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 6-1
REPLACEMENT PARTS LIST - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 7-1
LGE Internal Use Only Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
SPECIFICATIONS
ITEM DESCRIPTION
MODEL MS3046SQ
Power Requirement 230 V~ 50 Hz
Single phase, 3 wire grounded
Microwave 1300W
Power Output 900 watt full microwave power (IEC60705)
Microwave Frequency 2450 MHz
Magnetron 2M214 - 39F
Timer 0 ~ 99 min.
Outside Dimensions 512 (W) x 307 (H) x 420 (D)mm
Cavity Dimensions 348 (W) x 235 (H) x 366 (D)mm
Net Weight 16.5 kg
Shipping weight 18.5 kg
Control Complement Microwave Power for Variable Cooking
Power level
max. (900W) ................................... Full power throughout the cooking time
MED.-HIGH (720W) ....................... approx. 80% of Full power
MEDIUM (540W) ............................ approx. 60% of Full power
DEFROST (360W) ......................... approx. 40% of Full power
LOW/WARM (180W) ...................... approx. 20% of Full power
Rating Label Location
Back side
Accessories Owner's manual
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. 1-1 LGE Internal Use Only
Only for training and service purposes
CAUTIONS
Unlike other appliances, the microwave oven is
high-voltage and high-current equipment.
MICROWAVE RADIATION
Though it is free from danger in ordinary use, Personnel should not be exposed to the
extreme care should be taken during repair. microwave energy which may radiate from the
magnetron or other microwave generating
device if it is improperly used or connection.
· DO NOT operate on a 2-wire extension cord during All input and output microwave connections,
repair and use. waveguide, flange and gasket must be secure
· NEVER TOUCH any oven components or wiring during never operate the device without a microwave
operation. energy absorbing load attached.
· BEFORE TOUCHING any parts of the oven, always Never look into an open waveguide or antenna
remove the power plug from the outlet. while the device is energized.
· 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 · Proper operation of the microwave oven requires that
voltage capacitor by shorting across the two terminals the magnetron be assembled to the waveguide and
with an insulated screwdriver. 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
· Remove your watches whenever working close to or MAGNETRON
replacing the Magnetron.
· NEVER operate the oven with no load.
· NEVER injure the door seal and front plate of the oven
cavity.
· NEVER put iron tools on the magnetron. THE OVEN IS TO BE SERVICED ONLY
· NEVER put anything into the latch hole and the BY PROPERLY QUALIFIED SERVICE
interlock switches area.
PERSONNEL.
LGE Internal Use Only 2-1 Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
INSTALLATIONS
BEFORE YOU BEGIN, READ THE FOLLOWING INSTRUCTIONS COMPLETELY AND CAREFULLY.
INSTALLING EARTHING INSTRUCTIONS
1. Empty the microwave oven and clean inside it with This microwave oven is designed to be used in a fully
a soft, damp cloth. Check for damage such as earthed condition.
misaligned door, damage around the door or dents It is imperative, therefore, to make sure it is properly
inside the cavity or on the exterior. 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 WARNING-
utensils you put in it. (The control panel side of the THIS APPLIANCE
oven is the heavy side. Use care when handling.)
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. IMPORTANT
Make sure the microwave oven legs are in place to
ensure proper air flow. 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 Green-and-yellow: Earth
damage the electronic or mechanical parts of the Blue: Neutral
unit. Brown: 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
5. Use microwave oven in an ambient temperature
markings identifying the terminals in your plug,
less than 104°F(40°C).
proceed as follows.
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
7. Place the microwave oven as far away as possible with the letter E or by the earth symbol ( ) or
from TV, RADIO, COMPUTER, etc., to prevent colored green or green-and-yellow.
interference.
8. Do not touch the front glass during or after cooking The wire which is colored blue must be connected to
of the Grill and Combination mode. the terminal in the plug which is marked with the letter
This glass is very hot during heater operating. N or colored black.
9. Do not operate the oven at microwave and
combination mode with Grill rack placed in the The wire which is colored brown must be connected
cavity when the oven is empty. to the terminal in the plug which is marked with the
letter L or colored red.
10cm
Copyright © 2007 LG Electronics. Inc. All right reserved. 3-1 LGE Internal Use Only
Only for training and service purposes
OPERATING INSTRUCTIONS
FEATURES
Oven Front Plate
Window Door Screen
Door Seal
Key pad
Safety Door Lock System
Turntable Roller Rest
CONTROL PANEL
1. DISPLAY WINDOW: Used to show time of day,
power level of cooking, cooking category.
2. AUTO COOK: Used to select the auto cook.
1
3. KITCHEN TIMER
4. QUICK DEFROST: Used to defrost quickly 1Lb.
2
5. AUTO DEFROST: Used to select the desired auto
weight defrost programmed with weight pad.
6. MICRO: Used to select power level for cooking.
7. SET CLOCK: Used to set the time of day.
8. COOK TIME: Used to cook food for a desired time.
9. MORE/LESS: Used to change the cooking time &
3 4 desired weight.
5 10. STOP/CLEAR: Used to stop oven and clear all
6 7 entries except time of day.
11. START/QUICK START: To quickly set the
8 cooking time directly.
9
10 11
LGE Internal Use Only 4-1 Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
OPERATING SEQUENCE
The following is a description of component functions 5. CHILD LOCK
during oven operation. This oven has a CHILD LOCK feature.
To Set CHILD LOCK
1. SETTING THE CLOCK
Stop/Clear Stop/Clear
(Touch and Hold)
Stop/Clear Desired
Clock hour
To Cancel CHILD LOCK
Desired Start Stop/Clear
minute Stop/Clear
(Touch and Hold)
2. MICROWAVE COOKING
6. QUICK START
Desired Desired
Stop/Clear power cooking Start Stop/Clear Start
level time
7. MORE AND LESS
3. AUTO WEIGHT DEFROST
Stop/Clear Desired auto cook More
Desired Food
Stop/Clear defrost Start
weight Less
category
4. AUTO COOK
Desired Food
Stop/Clear auto cook Start
weight
category
Copyright © 2007 LG Electronics. Inc. All right reserved. 4-2 LGE Internal Use Only
Only for training and service purposes
SCHEMATIC DIAGRAM
LGE Internal Use Only 4-3 Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
CIRCUIT DESCRIPTION
GENERAL DETAILS WHEN THE OVEN IS SET AT ANY LEVEL
· The low voltage transformer supplies the necessary EXCEPT MAXIMUM.
voltage to the micom controller when power cord is
· The micom controller controls the ON-OFF time of
plugged in.
relay 2 by the applied signal to vary the average output
· When the door is closed, the primary switch is ON, the
power of microwave oven as POWER LEVEL.
secondary switch is ON, and the monitor switch opens
(refer to page 1-1)
(contact COM and NO).
· One complete cycle of relay 2 is 22 seconds.
WHEN SELECTING COOKING POWER WHEN THE DOOR IS OPENED DURING
LEVEL AND TIME COOKING
· The micom controller memorizes the function you set.
· Both the primary switch and relay 2 are cut off primary
· The time you set appears in the display window.
winding voltage of the high voltage transformer.
· Each indicator light turns on to indicate that the stage
· ON-OFF of relay 2 is coupled electrically with opening
has been set.
and closing of the secondary switch.
· When the door is opened, the secondary switch is
WHEN TOUCHING THE START PAD opened and when the door is closed, the secondary
· The coil of the relay is energized by the micom switch is closed.
controller. · The cooking time stops counting down.
· Power input is supplied to the high voltage transformer · Relay stops functioning.
through the fuse to the primary switch and relay 2. · As the door is opened, if the contact of primary switch
· Turntable rotates. and relay 2 and / or secondary switch fails to open, the
fuse opens due to the large current surge caused by
PRIMARY the monitor switch activation, which in turn stops
FUSE SWITCH
magnetron oscillation.
L FUSE
PRIMARY
H.V. SWITCH
MONITOR TRANS-
SWITCH FORMER
N L
H.V.
MONITOR TRANS-
SWITCH FORMER
RELAY 2 SECONDARY
SWITCH N
MICOM CONTROLLER
RELAY 2 SECONDARY
SWITCH
· The fan motor rotates and cools the magnetron by
MICOM CONTROLLER
blowing the air (coming from the intake on the
baseplate).
· The air is also directed into the oven to exhaust the
vapor in the oven through the upper plate.
· Cooking time starts counting down.
· 3.2 volts AC is generated from the filament winding of
the high voltage transformer. This 3.2 volts is applied to
the magnetron to heat the magnetron filament through
two noise-preventing choke coils.
· 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.
· The negative 4000 Volts DC is applied to the filament
of the magnetron.
Copyright © 2007 LG Electronics. Inc. All right reserved. 4-4 LGE Internal Use Only
Only for training and service purposes
SERVICE INFORMATION
TOOLS AND MEASURING INSTRUMENTS
NECESSARY TOOLS NECESSARY MEASURING INSTRUMENTS
Tools normally used for TV servicing are sufficient. · TESTER(VOLTS-DC, AC., Ohmmeter)
Standard tools are listed below. · Microwave survey meter
· Diagonal pliers - Holaday HI-1500
· Long nose pliers HI-1501
· Phillips screwdriver - Narda 8100
· Flat blade screwdriver 8200
· Wrench (size 5mm) · Inch scale
· Nutdriver (size 5mm) · 600 cc non conductive material beaker (glass or
· Adjustable wrench plastic), inside diameter: approx. 8.5 cm(31/2 in.)
· Soldering iron · Cylindrical and made of borosilicate glass vessel.
· Solder max. thickness: 3 mm
· Vinyl insulation tape outside diameter: approx. 190mm
· Polishing cloth height: approx. 90mm
· Glass thermometer: 100°C or 212°F (1 deg scale)
MICROWAVE LEAKAGE TEST
CAUTIONS MEASURING MICROWAVE ENERGY
LEAKAGE
· Be sure to check microwave leakage prior to
servicing the oven if the oven is operative prior to · Pour 275±15cc of 20±5°C(68±9°F) water in a beaker
servicing. which is graduated to 600 cc, and place the beaker
· The service personnel should inform the on the center of the turntable.
manufacture importer, or assembler of any certified · Set the energy leakage monitor to 2,450 MHz and
oven unit found to have a microwave emission use it following the manufacturer's recommended
level in excess of 5 mW/cm2 and should repair any test procedure to assure correct result.
unit found to have excessive emission levels at no cost · When measuring the leakage, always use the 2-
to the owner and should ascertain the cause of the inch (5cm) spacer supplied with the probe.
excessive leakage. The service personnel should · Operate the oven at its maximum output.
instruct the owner not to use the unit until the oven has · Measure the microwave radiation using and
been brought into compliance. electromagnetic radiation monitor by holding the
· If the oven operates with the door open, the service probe perpendicular to the surface being measured
personnel should:
- Tell the user not to operate the oven. Move probe along shaded area
- Contact the manufacturer.
· The service personnel should check all surface and Probe scanning speed
vent openings for microwave leakage. Less than 2.5 cm/sec
· Check for microwave leakage after every servicing. The (1in/sec)
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 5-1 Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
MEASUREMENT WITH OUTER CASE NOTES WHEN MEASURING
REMOVED · Do not exceed meter full scale deflection.
· When you replace the magnetron, measure for · The test probe must be removed no faster than
microwave energy leakage before the outer case is 1 inch/sec (2.5 cm/sec) along the shaded area,
installed and after all necessary components are otherwise a false reading may result.
replaced or adjusted. · The test probe must be held with the grip portion of the
Special care should be taken in measuring the handle.
following parts. (Circled area of below Fig.) A false reading may result if the operator's hand is
- Around the magnetron between the handle and the probe.
- The waveguide · When testing near a corner of the door, keep the probe
perpendicular to the surface making sure the probe is
moved horizontally along the oven surface, this may
WARNING : AVOID CONTACTING ANY possibly cause probe damage.
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. 5-2 LGE Internal Use Only
Only for training and service purposes
MEASUREMENT OF MICROWAVE POWER OUTPUT
· Microwave power output measurement is made with · The microwave power output P in watts is calculated
the microwave oven supplied at its rated voltage and from the following formula :
operated at its maximum microwave power setting
4187 x (T) + 0.55 X (T2 -T0 )X M
with a load of (1000 ± 5)g potable water. P=
· The water is contained in a cylindrical borosilicate T
glass vessel having a maximum material thickness
· T2 : Temperature after heating
of 3 mm and an outside diameter of approximately
· T0 : Temperature of bowl
190 mm.
· M : Weight of bowl
· The oven and the empty vessel are at ambient
temperature prior to the start of the test. is measured while the microwave generator is
· The initial temperature (±1) of the water is (10±2)°C. operating at full power. Magnetron filament heat-up
It is measured immediately before the water is time is not included.
added to the vessel. After addition of the water to · The water is stirred, to equalize temperature
the vessel, the load is immediately placed on the throughout the vessel, prior to measuring the final
center of the shelf which is in the lowest position and water temperature.
the microwave power switched on. · Stirring devices and measuring instruments are
· The time T for the temperature of the water to rise selected in order to minimize addition or removal of
by a value T of (10±2)°K is measured, where T is heat.
the time in seconds and T is the temperature rise. WATER LOAD
The initial and final water temperatures are selected
so that the maximum difference between the final
water temperature and the ambient temperature is
5 °K. TURNTABLE
DISASSEMBLY AND ADJUSTMENT
A. OUTER CASE REMOVAL C. CONTROLLER ASSEMBLY REMOVAL
1) Disconnect the power supply cord from the outlet. 1) Disconnect the leadwire from the PCB SUB ASS'Y.
2) Remove the screws from the rear and along side 2) Remove the screws for the earth and securing the
edges of the case. control panel.
The outer case must be moved backward to be lifted 3) Lift control panel ASS'Y from the oven by the tab
off. unhooked.
B. POWER SUPPLY CORD REMOVAL
1) Remove the outer case.
2) Disconnect two terminals, and remove one screw of
the earth terminal.
CAUTION: DISCHARGE THE HIGH VOLTAGE
CAPACITOR BEFORE SERVICING
(refer to page 2-1)
LGE Internal Use Only 5-3 Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
D. DOOR ASSEMBLY / REMOVAL F. AIR DUCT ASSEMBLY / REMOVAL
1) Open the door. 1) Disconnect the leadwire from lamp and MGT
2) Remove the choke cover very carefully with a flat- thermostat.
blade screwdriver. 2) Remove the mounting screw to the magnetron.
CAUTION: Be careful not to damage door seal plate
by screwdriver. G. MAGNETRON REMOVAL
3) Lift up and push the door.
1) Disconnect the leadwire from the high voltage
transformer and high voltage capacitor.
NOTE:
2) Carefully remove the mounting screws holding the
1. After replacing the door, be sure to check that the
magnetron and the waveguide.
primary switch, monitor switch, and secondary switch
3) Remove the magnetron ASS'Y until the tube is
operate normally.
clear from the waveguide.
2. After replacing the door, check for microwave energy
leakage with a survey meter. Microwave energy must
NOTE:
be below the limit of 5 mW/cm2. (with a 275 ml water
1. When removing the magnetron, make sure its
load)
dome does not hit any adjacent parts, or it may be
3. When mounting the door assembly to the oven
damaged.
assembly, be sure to adjust the door assembly parallel
2. When replacing the magnetron, be sure to install
to the chassis. Also adjust so the door has no play
the magnetron gasket in the correct position and
between the inner door surface and oven frame
be sure that the gasket is in good condition.
assembly. If the door assembly is not mounted
3. After replacing the magnetron, check for microwave
properly, microwaves may leak from the clearance
leakage with a survey meter around the
between the door and the oven.
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.
Magnetron
E. HIGH VOLTAGE TRANSFORMER
REMOVAL
1) Discharge the high voltage capacitor.
2) Disconnect the leadwire from magnetron, high voltage
transformer, and capacitor.
3) Remove the screw holding the high voltage
Air Duct
transformer to the baseplate.
Copyright © 2007 LG Electronics. Inc. All right reserved. 5-4 LGE Internal Use Only
Only for training and service purposes
H. FAN MOTOR ASSEMBLY / REMOVAL J. THE TURNTABLE MOTOR REMOVAL
1) Discharge the high voltage capacitor. 1) Remove the turntable.
2) Disconnect the leadwire from fan motor, noise filter 2) Remove the turntable shaft VERY CAREFULLY
and high voltage capacitor. with a slotted screwdriver.
3) Remove the two screws holding the the suction guide 3) Lay the unit down on its back.
ASS'Y to the oven cavity and remove the high voltage 4) Remove the turntable motor cover.
diode earth screw. The turntable base cover is easily removed by
4) Remove the screw of the capacitor bracket. pinching the six parts with a wire cutting.
5) Remove the two screws holding the fan motor ASS'Y 5) Disconnect the leadwire from the turntable motor
to the suction guide ASS'Y. terminals.
6) Remove the screw securing the turntable motor to
the oven cavity ASS'Y
I. HIGH VOLTAGE CAPACITOR AND 7) After repairing the motor, rotate the removed
DIODE REMOVAL turntable motor cover.
1) Discharge the high voltage capacitor. 8) Fit the turntable motor cover's projecting part to the
2) Disconnect the leadwire from fan motor, noise filter base plate slit.
and high voltage capacitor. 9) The taptite screw shall be used when a turntable
3) Remove the screw holding the suction guide ASS'Y to motor cover is secured with a screw.
the oven cavity and remove the high voltage diode
earth screw. NOTE:
4) Remove the screw holding the high voltage capacitor 1. Remove the wire lead from the turntable motor
bracket. VERY CAREFULLY.
2. Be sure to grasp the connector, not the wires, when
removing.
Suction
Guide
H.V.
Transformer H.V.
Capacitor
Taptite Screw
Wire Leads
Turntable Motor
LGE Internal Use Only 5-5 Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
K. PCB ASSEMBLY REMOVAL L. INTERLOCK SYSTEM
1) Remove the control panel assembly from the 1) INTERLOCK MECHANISM
cavity. (Refer to control panel assembly removal The door lock mechanism is a device which has
on previous page.) been specially designed to eliminate microwave
2) Remove screws which hold the PCB SUB ASS'Y to activity when the door is opened during cooking
the control panel. and thus to prevent the danger resulting from the
3) Disconnect the flat cable from the PCB SUB microwave leakage.
ASS'Y and take off the PCB SUB ASS'Y. 2) MOUNTING OF THE PRIMARY/MONITOR/
SECONDARY SWITCHES TO THE LATCH
BOARD
Control Panel ADJUSTMENT
DIRECTION
Key Membrane
PRIMARY
SWITCH
MONITOR
SWITCH
SECONDARY
SWITCH
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.
· Tighten the mounting screw.
· 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
adjustment. Make sure that the latch moves
smoothly after adjustment are completed and that
the screws are tight. Make sure the primary, monitor,
and secondary switches operate properly by
following the continuity test procedure.
CAUTION: CHECK THE CORRECT POSITION
FIG. 1
MAGNETRON
H.V. TRANSFORMER
H.V.
DIODE
H.V. CAPACITOR
PRIMARY
Copyright © 2007 LG Electronics. Inc. All right reserved. 5-6 LGE Internal Use Only
Only for training and service purposes
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 Disconnect the wire lead from the secondary
with the door closed, an audible click should be switch.
heard at the same time or successively at Connect the ohmmeter leads to the common
intervals. When the button is released slowly, the (COM) and normally open (NO) terminals of the
latches should activate the switches with an switch. The meter should indicate a open circuit in
audible click. the door open condition. When the door is closed,
If the latches do not activate the switches when meter should indicate an closed circuit. When the
the door is closed, the switches should be a secondary switch operation is abnormal, make the
adjusted in accordance with the adjustment necessary adjustment or replace the switch only
procedure. Disconnect the wire lead from the with the same type of switch.
primary switch. Connect the ohmmeter leads to
the common (COM) and normally open (NO) C. MONITOR SWITCH TEST
terminal of the switch. The meter should indicate
Disconnect the wire lead from the monitor switch.
an open circuit in the door open condition.
Connect the ohmmeter leads to the common
When the door is closed, the meter should
(COM) and normally closed (NC) terminals of the
indicate a closed circuit.
switch. The meter should indicate closed circuit in
When the primary switch operation is abnormal,
the door open condition. When the door is closed,
make the necessary adjustment or replace the
meter should indicate an open circuit. When the
switch only with the same type of switch.
monitor switch operation is abnormal, replace 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 Check for continuity of the switch Door Door
(Wire leads removed) with a Multi-meter open close
Primary NO
COM
Switch
NC
Monitor COM
Switch
Secondary COM
NO
Switch
NOTE : After checking for the continuity of switches, make sure that are
correctly connected.
LGE Internal Use Only 5-7 Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
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
TERMINAL
SECONDARY
TERMINAL
PRIMARY
TERMINAL
1. Measure the resistance.
(Ohm-meter scale: Rx1 and Rx100)
· Primary winding Approx.: 1.9 ohm
· Secondary winding Approx.: 90 ohm
· Filament winding Less than: 1 ohm
2. Measure the resistance.
(Ohm-meter scale: Rx1000)
· Primary winding to ground Normal: Infinite
· Filament winding to ground Normal: Infinite
MAGNETRON 1. Measure the resistance.
(Wire leads removed) (Ohm-meter scale: Rx1)
· Filament terminal Normal: Less than 1 ohm
2. Measure the resistance.
(Ohm-meter scale: Rx1000)
· Filament to chassis Normal: Infinite
Copyright © 2007 LG Electronics. Inc. All right reserved. 5-8 LGE Internal Use Only
Only for training and service purposes
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 Measure the resistance. Normal: Momentarily indicates
CAPACITOR (Ohm-meter scale: Rx1000) several ohms, and
· Terminal to terminal. then gradually returns
to infinite.
Measure the resistance. Normal: Infinite.
(Ohm-meter scale: Rx1000)
· Terminal to case.
HIGH VOLTAGE Measure the continuity (Forward). Normal: Continuity.
DIODE (Ohm-meter scale: Rx10000) Abnormal: Infinite.
NOTE :
Some inexpensive meters
may indicate infinite
resistance in both direction. Measure the continuity (Reverse). Normal: Infinite.
(Ohm-meter scale: Rx10000) Abnormal: Continuity.
LGE Internal Use Only 5-9 Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
COMPONENTS TEST PROCEDURE RESULTS
FUSE Check for continuity of the fuse with an
Normal Abnormal
multi-meter.
NOTE: If the fuse is blown, check the primary, the secondary, and the monitor switches,
H.V.D. and H.V.C. before replacing the fuse.
If the fuse is blown by improper switch operation replace the defective switch and the
fuse at the same time. Replace just the fuse if the switches operate normally.
MAGNETRON 0°C~Approx.110°C Approx.110°C
THERMOSTAT
Disconnect the 5 pin Check for P.C.B. connector. Cooking Start OFF
connector from P.C.B. 1 3 5
(Refer to schemetic diagram)
RELAY 2 OF P.C.B. Cooking Start OFF
(Wire leads removed.)
Note: Relay
Relay 2: Microwave
Relay 2
FAN MOTOR Measure the resistance. Normal: Approx.200 ~ 400 ohm
(Wire leads removed) (Ohm-meter scale: R x 1)
A Approx.30 ~ 50 ohm
A
B Approx.300 ~ 500 ohm
Abnormal: Infinite or several
B ohm.
TURNTABLE Measure the resistance.
MOTOR (Ohm-meter scale: R x 1000) Normal: Approx. 100 ~ 200
(Wire leads removed) Abnormal: Infinite or several
ohm.
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. 5-10 LGE Internal Use Only
Only for training and service purposes
TROUBLESHOOTING
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 circuitry on the digital programmer circuit since static electric discharge may
damage this control panel.
Always touch yourself ground while working on this panel to discharge any static charge built up in your
body.
CONDITION CAUSE REMEDY
Microwave oven Inserting many plug into one Avoid using other electrical
does not work. plug outle