Lg GMS-1120TW Microwave Service manual
The LG GMS-1120TW microwave oven offers a range of features to make cooking and reheating food convenient and efficient. With 11 power levels, including defrost and simmer settings, you can tailor the cooking process to various dishes. The spacious cavity accommodates larger dishes, and the turntable ensures even heat distribution. Additionally, the touch control panel provides easy operation, while the child lock feature enhances safety in your kitchen.
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MICROWAVE OVEN
SERVICE MANUAL
MODEL : GMS-1120TW
CAUTION
BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
P/NO : 3828W5S2299
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.
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
SCHEMATIC DIAGRAM OF P.C.B. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 8-1
PRINTED CIRCUIT BOARD - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 8-2
P.C.B. PARTS LIST - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 9-1
SPECIFICATIONS
ITEM
MODEL
Power Requirement
Power Output
Microwave Frequency
Magnetron
Timer
Outside Dimensions
Cavity Dimensions
Net Weight
Shipping weight
Control Complement
Accessories
DESCRIPTION
GMS-1120TW
120 Volts AC 60 Hz
1,500 Watts (13 A)
Single phase, 3 wire grounded
1,100 Watts full microwave power (IEC60705)
2,450 MHz
2M246
0 ~ 99 min. 99 sec.
20
1/8
”
(W) x 12
”
(H) x 15
5/16
”
(D)
13 7/8
”
(W) x9 5/16
”
(H) x 14 3/16
”
(D)
33 lbs (approx.)
35 lbs (approx.)
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, 8 (Reheat) --------approx. 80%
7 (Med.-High) --------------------approx. 70%,
5 (Med.-Low) --------------------approx. 50%,
3 (Low) ---------------------------approx. 30%,
1 (Warm)--------------------------approx. 10%
6 (Medium) --------approx. 60%
4 (Defrost) ---------approx. 40%
2 (Simmer)---------approx. 20%
Owner's manual & cooking guide
Glass turntable
Rotating ring
It is not recommended for commercial purposes.
1-1
CAUTIONS
Unlike other appliances, the microwave oven is high-voltage and high-current equipment.
Though it is free from danger in ordinary use, extreme care should be taken during repair.
• 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.
MICROWAVE RADIATION
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.
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
MAGNETRON
CHASSIS GROUND
• 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.
• NEVER put iron tools on the magnetron.
• NEVER put anything into the latch hole and the interlock switches area.
THE OVEN IS TO BE SERVICED ONLY
BY PROPERLY QUALIFIED SERVICE
PERSONNEL.
2-1
INSTALLATIONS
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.
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.)
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.
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.
Do not install the oven next to a conventional surface unit or above a conventional wall oven.
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.
7. Place the microwave oven as far away as possible from TV, RADIO, COMPUTER, etc., to prevent interference.
GROUNDING INSTRUCTIONS
For personal safety, this appliance must be fully grounded at all times.
In the event of an electrical short circuit, grounding reduces the risk of electrical shock.
The plug must be plugged into an outlet that is properly installed and grounded.
WARNING
Improper use of the grounding plug can result in a risk of electric shock.
Do not, under any circumstances, cut or remove the third ground prong from the power cord plug.
PREFERRED METHOD
ENSURE PROPER GROUND
EXISTS BEFORE USE
TEMPORARY METHOD
(ADAPTER PLUGS NOT
PERMITTED IN CANADA)
ALIGN LARGE
PRONGS/SLOTS
10cm
ENSURE PROPER GROUND
AND FIRM CONNECTION
BEFORE USE
3-1
OPERATING INSTRUCTIONS
FEATURES
Window Door Screen
Oven Front Plate
Door Seal
Display Window
Control Panel
Turntable
Safety Door Lock System
Rotating Ring
CONTROL PANEL
4-1
1. DISPLAY. The display includes a clock and indicators that tell you time of day, cooking time settings, and cooking functions selected.
2. ONE TOUCH POPCORN. Touch this pad to pop a bag of microwave popcorn without entering a cook power or time.
3. ONE TOUCH POTATO. Touch this pad to cook up to 4 potatoes without entering a cook power or time.
4. ONE TOUCH BEVERAGE. Touch this pad to heat up to
2 cups of beverage without entering a cook power or time.
5. ONE TOUCH FOOD PLATE. Touch this pad to heat a plate of food without entering a cook power or time.
6. FRESH VEGETABLE. Touch this pad to cook fresh vegetables without entering a cook power or time.
7. FROZEN ENTREE. Touch this pad to cook a 10 oz.
frozen entrée without entering a cook power or time.
8. ONE TOUCH PIZZA: Touch this pad to heat up to 3 slices of regrigerated pizza without entering a cook power or time.
9. AUTO DEFROST. Touch this pad to meat, poultry, or steaks/chops by entering a weight.
10. CLOCK. Touch this pad to enter the time of day.
11. NUMBER PADS. Touch number pads to enter cooking time, power level, quantities, or weights.
12. TIME. Touch this pad to set a cooking time.
13. POWER. Touch this pad to set a cooking power.
14. STOP/CLEAR. Touch this pad to stop the oven or clear entries.
15. EZ ON. Touch this pad to cook at 100% cook power for
30 seconds to 99 minutes, 59 seconds.
16. START. Touch this pad to start all entries (except the
ONE TOUCH and EZ ON functions, which start automatically).
OPERATING SEQUENCE
The following is a description of component functions during oven operation.
1. SETTING THE CLOCK
STOP/CLEAR CLOCK NUMBER CLOCK ex.) To set 4:30, touch number key [4],[3], and [0].
NOTE: 1) This is a 12 hour clock.
2) Clock will operate as long as power is applied to the oven.
2. CANCEL FUNCTION
cancel an entry or a function currently in use.
The display will either return to the last item entered or to the clock.
3. EZ ON
STOP/CLEAR EZ on
7. AUTO DEFROST COOKING
START/PAUSE
AUTO
DEFROST
NUMBER
OF WEIGHT
8. CHILD LOCK
This oven has a CHILD LOCK feature
TO SET CHILD LOCK
START
LOCK appear on the display.
TO CANCEL CHILD LOCK
LOCK
disappears on the display.
4. ONE TOUCH COOKING
STOP/CLEAR POPCORN
NOTE: Heat only 1 package at a time
5. TIME COOKING
STOP/CLEAR TIME
NUMBER
NUMBER
START
POWER
6. MULTI-STAGE COOKING
1ST STAGE
STOP/CLEAR TIME NUMBER
NUMBER
2ND STAGE
TIME
NUMBER
NUMBER
START
POWER
POWER
4-2
SCHEMATIC DIAGRAM
4-3
CIRCUIT DESCRIPTION
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).
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.
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.
FUSE
N
MONITOR
SWITCH
H.V.
TRANS-
FORMER
• 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 4,000 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)
• One complete cycle of the relay 2 is 22 seconds.
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.
• The cooking time stops counting down.
• Relay stops functioning.
• 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.
PRIMARY
SWITCH
RELAY 2
SECONDARY
SWITCH
N
MICOM CONTROLLER
MONITOR
SWITCH
H.V.
TRANS-
FORMER
• The fan motor rotates and cools the magnetron by 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.
• 3.3 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.
FUSE
PRIMARY
SWITCH
RELAY 2
MICOM CONTROLLER
SECONDARY
SWITCH
4-4
SERVICE INFORMATION
TOOLS AND MEASURING INSTRUMENTS
NECESSARY TOOLS
Tools normally used for TV servicing are sufficient.
Standard tools are listed below.
• Diagonal pliers
• Long nose pliers
• Phillips screwdriver
• Flat blade screwdriver
• Wrench (size 5mm)
• Nutdriver (size 5mm)
• Adjustable wrench
• Soldering iron
• Solder
• Vinyl insulation tape
• Polishing cloth
NECESSARY MEASURING INSTRUMENTS
• TESTER (VOLTS-DC, AC, Ohmmeter)
• Microwave survey meter
- Holaday HI-1500
HI-1501
- Narda 8100
8200
• Inch scale
• 600 cc non conductive material beaker (glass or plastic), inside diameter: approx. 8.5 cm (3
1
/2 in.)
• 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 level in excess of 5 mW/cm 2
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.
• The service personnel should check all surface and vent openings for microwave leakage.
• 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/cm 2 . Always start measuring of an unknown field to assure safety for operating personnel from radiation leakage.
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
Move probe along shaded area
Probe scanning speed
Less than 2.5 cm/sec
(1 in/sec)
5-1
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
- The waveguide
WARNING : AVOID CONTACTING ANY
HIGH VOLTAGE PARTS
NOTES WHEN MEASURING
• Do not exceed meter full scale deflection.
• The test probe must be removed 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 with 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; this may cause probe damage.
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.
5-2
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 the 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 temperature and the ambient temperature is 5°K.
• The microwave power output P in watts is calculated from the following formula :
P =
4187 x (
∆
T)
T 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.
WATER LOAD
TURNTABLE
DISASSEMBLY AND ADJUSTMENT
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 leadwire from RELAY (RY2) of the
PCB SUB ASSEMBLY.
3) Disconnect the leadwire from connector (CN1) of the
PCB SUB ASSEMBLY.
4) Lift up and pull out control panel assembly carefully from the cavity.
Remove the screw securing screw ground screw
Lift up and pull out control panel
CAUTION: DISCHARGE THE HIGH VOLTAGE
CAPACITOR BEFORE SERVICING
(refer to page 2-1)
5-3
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
ASSEMBLY to the control panel.
3) Disconnect the flat cable from the PCB SUB
ASSEMBLY and take off the PCB SUB ASSEMBLY.
Control Panel
PCB Sub Asm
Key Membrane
Remove choke cover
Remove door
Button Spring
Door Open Button
Release
Lever
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.
2. After replacing the door, check for microwave energy leakage with a survey meter. Microwave energy must be below the limit of 4 mW/cm. (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.
5-4
Spacer
F. AIR DUCT ASSEMBLY REMOVAL
1) Disconnect the leadwire from the lamp.
2) Remove the mounting screw to the oven cavity.
G. MAGNETRON REMOVAL
1) Disconnect the leadwire from the magnetron.
2) Carefully remove the mounting screw holding the magnetron and cavity.
3) Carefully remove the mounting screws holding the magnetron and the waveguide.
4) Remove the magnetron ASSEMBLY 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/cm 2 . (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.
H. REMOVING THE TURNTABLE MOTOR
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 ASSEMBLY.
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.
NOTE:
1. Remove the wire lead from the turntable motor
VERY CAREFULLY.
2. Be sure to grasp the connector, not the wires, when removing.
Waveguide
Dome
Waveguide
Bracket
Magnetron
Gasket
Magnetron
Air Duct
Magnetron
5-5
Turntable
Motor
Wire Leads
I. 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 transformer to the baseplate.
J. FAN MOTOR ASSEMBLY REMOVAL
1) Discharge the high voltage capacitor.
2) Disconnect the leadwire from fan motor and high voltage capacitor.
3) Remove the two screws holding the the suction guide
ASSEMBLY to the oven cavity and remove the high voltage diode earth screw.
4) Remove the two screws holding the fan motor
ASSEMBLY to the suction guide ASSEMBLY.
K. HIGH VOLTAGE CAPACITOR AND
DIODE REMOVAL
1) Discharge the high voltage capacitor.
2) Disconnect the leadwire from fan motor and high voltage capacitor.
3) Remove the screw holding the suction guide
ASSEMBLY to the oven cavity and remove the high voltage diode earth screw.
4) Remove the screw holding the high voltage capacitor bracket.
Fan Motor
ASS'Y
H.V.
Transformer
Suction
Guide
H.V.
Capacitor
H.V.
Diode
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.
ADJUSTMENT
DIRECTION
SECONDARY
SWITCH
MONITOR
SWITCH
PRIMARY
SWITCH
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.
• 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 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.
5-6
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
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.
When the primary switch operation is abnormal, make the necessary adjustment or replace the switch only with the same type of switch.
COMPONENTS
SWITCHES
(Wire leads removed)
B. SECONDARY INTERLOCK SWITCH TEST
TEST PROCEDURE
Check for continuity of the switch with an Ohm-meter
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.
NOTE: After repairing the door or the interlock system, it is necessary to do this continuity test before operating the oven.
Door open
RESULTS
Door closed
Primary
Switch COM
NO
Monitor
Switch
Secondary
Switch
COM
NC
COM
NO
NOTE : After checking for the continuity of switches, make sure that they are connected correctly.
5-7
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
HIGH VOLTAGE
TRANSFORMER
(Wire leads removed)
TEST PROCEDURE RESULTS
MAGNETRON
(Wire leads removed)
1. Measure the resistance.
(Ohm-meter scale: Rx1 and Rx100)
• Primary winding
• Secondary winding
• Filament winding
2. Measure the resistance.
(Ohm-meter scale: Rx1000)
• Primary winding to ground
• Filament winding to ground
1. Measure the resistance.
(Ohm-meter scale: Rx1)
• Filament terminal
2. Measure the resistance.
(Ohm-meter scale: Rx1000)
• Filament to chassis
Approx.: 0.2 ~ 0.4 ohm
Approx.: 60 ~ 90 ohm
Less than: 1 ohm
Normal: Infinite
Normal: Infinite
Normal: Less than 1 ohm
Normal: Infinite
5-8
COMPONENTS
HIGH VOLTAGE
CAPACITOR
TEST PROCEDURE
Antenna
Gasket
Chassis
RESULTS
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.
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.
HIGH VOLTAGE
DIODE
Measure the continuity (Forward).
(Ohm-meter scale: Rx10000)
Normal: Continuity.
Abnormal: Infinite.
NOTE :
Some inexpensive meters may indicate infinite resistance in both direction.
Measure the continuity (Reverse).
(Ohm-meter scale: Rx10000)
Normal: Infinite.
Abnormal: Continuity.
5-9
COMPONENTS
RELAY 2
TEST PROCEDURE
Check for continuity of relay 2 with an ohm-meter.
(Remove wire leads from relay 2 and operate the unit.)
RESULTS
POWER
LEVEL
7
8
5
6
3
4
1
2
9
10
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
FAN MOTOR
(Wire leads removed)
Relay 2
Measure the resistance.
(Ohm-meter scale: R x 1)
Normal:
A: Approx. 85 ~ 100 ohm.
B: Approx. 10 ~ 25 ohm.
Abnormal: Infinite or several ohms.
B
A
TURNTABLE
MOTOR
(Wire leads removed)
Measure the resistance.
(Ohm-meter scale: R x 1 )
Normal: Approx.100~150 ohm
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.
5-10
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
Microwave oven does not work.
Output power is too low.
Sparks occur.
Uneven cooking.
CAUSE
Inserting many plugs into one outlet and using them at the same time.
(blown fuse or breaker)
Microwave oven plug is not inserted tightly.
Low AC input voltage.
Food temperature is too low.
Using metallic ware and allowing it to touch the oven wall.
Ceramic ware trimmed in gold or silver powder is used.
Inconsistent intensity of microwave by their characteristics.
REMEDY
Avoid using other electrical appliances when you use the microwave oven.
Insert microwave oven plug securely.
Use the microwave oven at adequate line voltage.
This may not be a defect.
It is possible that the food should be cooked for a longer time period.
Do not use metallic ware for cooking except that noted in the cooking guide.
Do not use any type of cookware with metallic trimming.
1. Use plastic wrap or lid.
2. Stir once or twice while cooking soup, cocoa or milk, etc.
5-11
(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
1. No input can be programmed.
2. Some inputs cannot be programmed.
3. Display shows a number or figure different from one touched.
4. Random programming when touching other pads.
5. Display is fixed at some figure and can not accept any input.
CHECK
Check the connection between membrane key assembly and
PCB assembly.
Replace key membrane assembly and check operation.
RESULT
Continuity
No continuity
Everything works as specified.
Still have trouble.
CAUSE
Defective PCB assembly.
Loose connection.
Defective key membrane assembly.
Defective PCB assembly.
REMEDY
Replace PCB assembly.
Connect them tightly.
Replace key membrane assembly.
Replace PCB assembly.
5-12
(TROUBLE 2) Oven does not operate at all, Display window does not display any figures, and no input is accepted.
CONDITION
1. Fuse blows.
CHECK
Check continuity of monitor switch (with door closed).
Replace fuse
Check continuity of primary switch (with door opened).
RESULT
Continuity.
No continuity.
CAUSE
Malfunction of the monitor switch.
REMEDY
Replace fuse, primary, monitor, secondary switches, and
RELAY(RY2) of
P.C.B Assembly.
Check continuity of secondary switch (with door opened).
Disconnect one side of the wire lead connected from transformer to the high voltage capacitor and operate the unit.
Continuity.
No continuity.
Continuity.
No continuity.
Normal.
Fuse blows again
Shorted contact at the primary switch.
Malfunction of secondary switch.
Defective high voltage capacitor.
Defective high voltage transformer.
Replace fuse, primary, monitor, secondary switches, and
RELAY(RY2) of
P.C.B Assembly.
Replace fuse, primary, monitor, secondary switches, and
RELAY(RY2) of
P.C.B Assembly.
Replace high voltage capacitor.
Replace high voltage transformer.
NOTE : All these switches must be replaced at the same time. Refer to page 5-7, 5-8
2. Fuse does not blow.
Check continuity of thermostat.
No continuity.
Continuity.
Defective thermostat.
Replace thermostat.
Check continuity of power supply cord.
No continuity.
Defective power supply cord.
Replace power supply cord.
5-13
(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 RESULT
1. Setting time does not count down when touching START pad.
CHECK
Check continuity of secondary switch (with door closed).
No continuity.
Continuity.
CAUSE
Defective secondary switch.
REMEDY
Replace secondary switch.
2. Fan motor or oven lamp do not turn on.
Check the connection between
CN1 connector and PCB assembly.
Check fan motor.
Check oven lamp.
Continuity
No continuity
Abnormal
Abnormal
Normal
Defective PCB assembly.
Loose connection.
Defective fan motor.
Defective oven lamp.
Replace PCB assembly.
Connect them tightly.
Replace fan motor.
Replace oven lamp.
(TROUBLE 4) Oven seems to be operating but little heat is produced in oven load.
CONDITION CHECK RESULT CAUSE REMEDY
Output is low
Check the power source voltage.
Lower than 90% of rating voltage.
Normal
Abnormal
Decrease in power source voltage with load.
Defective PCB assembly.
Suggest customer contact local electric power utility co. or qualified electrician.
Replace PCB assembly.
Disconnect the wire leads from relay 2 and check on and off time with multitester.
Normal
Measure the output power.
Abnormal
Defective magnetron.
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.
Replace magnetron.
5-14
(TROUBLE 5) No microwave oscillation even though oven lamp and fan motor run.
(Display operates properly)
RESULT CONDITION
No microwave oscillation.
CHECK
Disconnect the wire leads from relay 2 and check continuity of relay 2.
(Operate the unit)
No continuity.
Continuity.
CAUSE
Defective PCB assembly.
REMEDY
Replace PCB assembly.
Check high voltage transformer
Abnormal
Normal
Defective high voltage transformer.
Replace high voltage transformer.
Check high voltage capacitor.
Abnormal
Normal
Defective high voltage capacitor.
Replace high voltage capacitor.
Check high voltage diode.
Abnormal
Normal
Defective high voltage diode.
Replace high voltage diode.
Check magnetron.
Abnormal
Defective magnetron.
Replace magnetron.
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 wire leads from relay 2 and check continuity relay 2.
(Operate the unit)
Abnormal.
5-15
#EV#
INTRODUCTION
EXPLODED VIEW
OVEN CAVITY PARTS
INTERIOR PARTS
DOOR PARTS
BASE PLATE PARTS
LATCH BOARD PARTS
CONTROL PANEL PARTS
6-1
#EV#
DOOR PARTS
13581A
13720D
13352A
13213A
13552A
15006A
13536A
14970A
14026A
6-2
#EV#
CONTROLLER PARTS
24781M
23506A
23572A
23550D
268711
WTP018
24510L
250201
24970A
6-3
#EV#
OVEN CAVITY PARTS
33112U
WTT021
33052A
36549S
WTP013
33390G
35889A
6-4
WTT010
#EV#
LATCH BOARD PARTS
43500A
6-5
466001
466003
466001
WSZ085
#EV#
INTERIOR PARTS
948504
54912B
948503
56930V
568771
WSZ002
56411A
WSZ002
56201A
WSZ002
WTT028
54974S
50FZZA
56549A
55900A
WTT037
WSZ002
55262A
WSZ002
WSZ002
50CZZH
34930W
56324A
WSZ002
948502
54810C
56201B
56851D
WTT028
WSZ002
6-6
#EV#
BASE PLATE PARTS
63303A
63302A
647781
WTT028
56170D
948501
WSZ002
WTT021
6-7
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Frequently asked questions
The dimensions of the LG GMS-1120TW microwave oven are 201/8" (W) x 12" (H) x 155/16" (D).
The LG GMS-1120TW microwave oven has a power output of 1,100 Watts full microwave power (IEC60705).
The LG GMS-1120TW microwave oven has a microwave frequency of 2,450 MHz.
The LG GMS-1120TW microwave oven has 10 power levels: HIGH, 9 (Saute), 8 (Reheat), 7 (Med.-High), 6 (Medium), 5 (Med.-Low), 4 (Defrost), 3 (Low), 2 (Simmer), and 1 (Warm).
The LG GMS-1120TW microwave oven comes with an owner's manual & cooking guide, glass turntable, and rotating ring.