LG LMV1762SB User manual

MICROWAVE OVEN
SERVICE MANUAL
MODEL: LMV1762SB
LMV1762SW
LMV1762ST
LMV1763ST
CAUTION
BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
P/NO : MFL06272540
March, 2016
Printed in Korea
Internal Use Only

-2-
CAUTION
WARNING TO SERVICE TECHNICIANS
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.
• Proper operation of the microwave oven requires that the magnetron be assembled to the wave guide 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.
• Routine service safety procedures should be exercised at all times.
• Untrained personnel should not attempt service without a thorough review of the test procedures and safety
information contained in this manual.

FOREWORD
Read this manual carefully. Failure to adhere to or observe the information in this manual may result in exposing
yourself to the microwave energy normally contained within the oven cavity.
CONTENTS
(Page)
Safety Precautions .............................................................................................................................................. 2
1. Specifications .................................................................................................................................................. 4
2. Cautions ........................................................................................................................................................... 5
3. Installation ....................................................................................................................................................... 6
4. Operation ......................................................................................................................................................... 7
4-1. Control Panel Features .............................................................................................................................. 7
4-2. Explanation of Control Panel...................................................................................................................... 8
5. Wiring Diagram / Key Matrix........................................................................................................................... 9
5-1. Wiring Diagram .......................................................................................................................................... 9
5-2. Key Matrix ............................................................................................................................................... 10
6. Troubleshooting ............................................................................................................................................ 11
6-1. General Information for Service ............................................................................................................... 11
6-2. Safety Caution.......................................................................................................................................... 12
6-3. Basic Check Summary............................................................................................................................. 13
6-4. Troubleshooting........................................................................................................................................ 14
7. Microwave Leakage Test .............................................................................................................................. 24
8. Power Output Measurement......................................................................................................................... 26
9. Interlock System............................................................................................................................................ 27
9-1. Interlock Mechanism ................................................................................................................................ 27
9-2. Interlock Continuity Test ........................................................................................................................... 29
10. Component Testing Information ................................................................................................................ 30
11. Disassembly Instructions ........................................................................................................................... 34
12. Exploded View ............................................................................................................................................. 41
-3-

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1. SPECIFICATIONS
Rated Power Consumption ................................ 1600W maximum (Microwave oven+Cook top lamps+Ventilation fan)
Microwave Output............................................... 1000W (IEC60705)
Frequency .......................................................... 2450 MHz ±50 MHz
Power Supply .................................................... 120 VAC, 60 Hz
Rated Current .................................................... 14 Amp. (Microwave oven+Cook top lamps+Ventilation fan)
Magnetron Cooling ............................................ Forced Air Cooling
Rectification ....................................................... Rectification Voltage Double Half-Wave
Door Sealing ...................................................... Choke System
Safety Devices ................................................... OVEN TCO 110/0
............................................................................ MGT TCO 150/0
............................................................................ Bottom TCO : 150/0
............................................................................ Fuse (20A)
............................................................................ Primary Interlock Switch
............................................................................ Secondary Interlock Switch
............................................................................ Interlock Monitor Switch
Magnetron ......................................................... 2M214 - 161GP
Cook Top Lamp ................................................. 125 V, 30 W or 40 W
Cavity Lamp ....................................................... 125 V, 30 W or 40 W
Timer ................................................................. Digital, up to 99 min. 99 sec. (in each cooking stage)
Tray ................................................................... Tempered Safety Glass
Overall Dimensions ........................................... 2915/16” (W) x 167/16” (H) x 1615/16” (D)
Oven Cavity Size ............................................... 219/16” (W) x 141/8” (H) x 8 7/8” (D)
Effective Capacity of Oven Cavity ..................... 1.7cu.ft.
Accessories ....................................................... Ownerʼs Manual & Cooking Guide, Installation Manual,
............................................................................ Exhaust Adapter, Exhaust Damper, Mounting Kit and Filter,
............................................................................ Glass Tray, Metal Rack, Rotating Ring Assembly.
SWITCH CHART
SWITCH MODE
CONDITIONS
OPEN OPEN CLOSE
CLOSE CLOSE OPENDOOR CLOSED
PRIMARY
INTERLOCK
SWITCH
SECONDARY
INTERLOCK
SWITCH
INTERLOCK
MONITOR
SWITCH
COM
NO
COM
NO
COM
NC
NOTE: Use the above switch chart with circuit diagram on page 5-1.
DOOR OPEN

-5-
2. 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.
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 connected.
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.
• 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.
• 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 the
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.
• 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.
THE OVEN IS TO BE SERVICED ONLY
BY PROPERLY QUALIFIED SERVICE
PERSONNEL.
Gasket
ANTENNA
COOLING FIN
MAGNETRON
CHASSIS GROUND FILAMENT
TERMINALS
MAGNETRON

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3. INSTALLATION
BEFORE YOU BEGIN, READ THE FOLLOWING INSTRUCTIONS COMPLETELY AND CAREFULLY.
PRECAUTIONS ON INSTALLATION
A. Plug the power supply cord into a 120V AC, 60Hz,
single-phase power source with a capacity of at
least 20 amperes.
B. Avoid placing the unit in a location where there is
direct heat or splashing water.
C. Install the unit on the mounting plate firmly.
D. Place the unit as far away as possible from TV,
radio, 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 electric shock.
The plug must be plugged into an outlet that is
properly installed and grounded.
CAUTION
This unit is equipped with a 3-prong plug for your
safety. If the wall outlet is a grounded 3-hole type,
the unit will be grounded automatically.
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.

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4. OPERATION
4-1. Control Panel
12
14
15
17
23
20
16
21
22
19
13
2
3
1
6
7
9
11
8
10
4
5
18

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4-2. Explanation of Control Panel
1. DISPLAY. The Display includes a clock and
indicators to tell you time of day, cooking time
settings and cooking functions selected.
2. Popcorn. Touch this pad when popping popcorn
in your microwave oven.
3. Potato. Touch this pad to cook up to 4 potatoes
without entering a cook time or power.
4. Frozen Entree. uch this pad to cook a 10 to 20
ounce (284 to 567 g) frozen entree without
entering a cook time or power.
5. Auto Cook. Tuch this pad to cook microwavable
foods without entering a cook time or power.
6. Soften. Touch this pad to soften butter, icecream,
cream cheese,frozen juice.
7. Melt. Touch this pad to melt butter or
margarine, chocolate,cheese,marshmallow.
8. Time. Touch this pad followed by number pads to
set a cooking time.
9. NUMBER- Touch number pads to enter cooking
time, power level, quantities or weights.
10. Less. Touch this pad to subtract ten seconds of
cooking time each time you press it.
11. Light On/Off. Touch this pad to turn the cooktop/
countertop light on or off.
12. Pizza. Touch this pad to reheat one or several
slices of pizza without entering a cook time or
power.
13. Auto Reheat. Touch this pad to reheat
microwavable foods without entering a cook time
or power.
14. Time Defrost. Touch this pad to set a defrost
time.
15. Auto Defrost. Touch this pad followed by
number pads to thaw frozen meat by weight.
16. Power Level. Touch this pad to select a cooking
power level.
17. Clock. Touch this pad to enter the time of day.
18. START Enter. Touch this pad to start a function.
If you open the door after oven begins to cook,
retouch START Enter.
19. STOP Clear. Touch this pad to stop the oven or
clear all entries.
20. Energy Saving. Touch this pad to save energy.
21. More. Touch this pad to add ten seconds of
cooking time each time you press it.
22. Add 30 Sec. Touch this pad to add 30 seconds
of cooking time each time you press it.
23. Vent Hi/Low/Off. Touch this pad to turn the Vent
on or off.
NOTE: If you try to enter incorrect instructions,
you will not hear any tones. Touch STOP Clear and
re-enter the instructions.

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5. WIRING DIAGRAM / KEY MATRIX
5-1. Wiring Diagram
BR
PK
YL
BK
BK
BK
RY8
C/T Lamp
RY9
Vent Slow
RY3
Vent High
RY4
Vent Low
FUSE
SR5
SMPS
1
3
4
5
6
7
8
9
SECONDARY
SWITCH
1
2
BOTTOM
BR
BL
RD
YL
DIODE
BL
H.V.FUSE
H.V.CAPACITOR
H.V.TRANSFORMER
MONITOR SWITCH
WH
RY2
POWER
RY1
Oven Lamp
RV
U
MGT
GN
9
BK BL WH PK BR GY

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5-2. Key Matrix
KEY MATRIX
Turntable On/Off
Power LevelTime CookHold WarmC/T Lamp On/OffStart
13
MoreSensor Cook
time & weight
Defrost
N.AN.A
N.A
N.A
Sensor Popcorn
12
LessSensor ReheatTimer
0
987
11
Melt
654
321
10
SoftenQuick DefrostAdd 30 Sec.Energy SavingClockVent Hi/Low/OffClear
9
8
76543212st
KEY MATRIX