LG LMHM2017ST, LMHM2017SB, LMHM2017SW Service Manual

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MICROWAVE OVEN

SERVICE MANUAL

MODEL: LMHM2017SW

CAUTION

BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.

P/NO : MFL06272512

LMHM2017SB LMHM2017ST

February, 2010

Printed in China

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 ovens 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.

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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. Specification .................................................................................................................................................... 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 .............................................................................................................................. 25

8. Power Output Measurement......................................................................................................................... 27

9. Interlock System............................................................................................................................................ 28

9-1. Interlock Mechanism ................................................................................................................................ 28

9-2. Interlock Continuity Test........................................................................................................................... 30

10. Component Testing Information................................................................................................................ 31

11. Disassembly Instructions........................................................................................................................... 35

12. Exploded View ............................................................................................................................................. 43

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1. SPECIFICATIONS

Rated Power Consumption ................................1815W maximum

(Microwave oven+Cook top lamps+Ventilation fan)

Microwave Output ...............................................1100W (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 ...................................................Magnetron Thermostat: Open at 150 °C ±5 °C

Close at 0 °C ±5 °C

............................................................................Oven Thermostat: Open at 145 °C ±5 °C

Close at 0 °C ±5 °C

............................................................................Heater Thermostat: Open at 145 °C ±5 °C

Close at 0 °C ±5 °C

............................................................................Fuse (20A)

............................................................................Primary Interlock Switch

............................................................................Secondary Interlock Switch

............................................................................Interlock Monitor Switch

Heater ................................................................120 V, 400W (Sheath)

Magnetron ..........................................................2M246 (LG)

Cook top Lamp ...................................................125V, 30W (Incandescent)

Warming Lamp ...................................................125V, 30W

Timer ..................................................................Digital,up to 99 min.(in each cooking stage)

Tray ....................................................................Tempered Safety Glass

Overall Dimensions ............................................2914/16

Oven Cavity Size ...............................................21

” (W) x 17

” (W) x 10

/16

”(H) x 14

” (H) x 15

” (D)

/16

” (D)

Effective Capacity of Oven Cavity ......................2.0 Cu.ft.

Accessories ........................................................Owner ’s Manual &Cooking Guide, Installation Manual,

............................................................................Exhaust Adapter, Exhaust Damper, Mounting Kit and Filter,

............................................................................Rotating Ring Assembly, Glass Tray, Metal Rack, Defrost Plate.

SWITCH CHART

PRIMARY

SWITCH MODE

CONDITIONS

DOOR OPEN DOOR CLOSED

NOTE: Use the above switch chart with circuit diagram on page 9.

INTERLOCK

SWITCH

COM

OPEN OPEN CLOSE

CLOSE CLOSE OPEN

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SECONDARY

INTERLOCK

SWITCH

COM

INTERLOCK

MONITOR

SWITCH

COM

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.

• 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 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.

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.

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THE OVEN IS TO BE SERVICED ONLY BY PROPERLY QUALIFIED SERVICE PERSONNEL.

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 electrical 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 Features

12 3 4 6 7 9 11 13

5 8 10 12 14

2217

2423 25

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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 setting, and cooking functions selected.

2. REHEAT Touch this pad to reheat Pizza Slice, Dinner Plate, Soup/Sauce, and Casserole. The oven’s sensor will tell the oven how long to cook depending on the amount of humidity coming from the food.

3. COOK Touch this pad to cook Baked Potato, Vegetable Casserole, Rice, and Frozen Entrée. The oven’s sensor will tell the oven how long to cook depending on the amount of humidity coming from the food.

4. POPCORN Touch this pad when popping popcorn in your microwave oven. The oven’s sensor will tell the oven how long to cook depending on the amount of humidity it detects from the popcorn.

5. KIDS MEAL Select type of dish to reheat HOT DOG, MAC & CHEESE or CHICKEN NUGGETS.

6. WARMING Touch this pad to keep hot cooked foods warm in your oven.

7. DEFROST Touch this key to defrost food by entering weight, cook time or Quickly. Touch this key 2 times to Quick Defrost Cook. Touch this key 3 times to Time Defrost Cook.

8. CLOCK Touch this pad to enter the time of day.

9. SOFTEN Touch this pad to soften Butter, Ice Cream, Cream Cheese, and Frozen Juice.

10. TIMER Touch this pad to set the kitchen timer.

13. EZ-ON Touch this pad to set and start quickly at 100% power level.

14. CUSTOM SET Touch this pad to change the oven’s default setting for sound, clock, disply speed, and defrost weight.

15. TURNTABLE ON/OFF Touch this pad to turn on/off the turntable. This option is not available in sensor cook and detrost modes.

16. POWER LEVEL Touch this pad to select a cooking power level.

17. NUMBER Touch number pads to enter cooking time, power level, quantities, or weights.

18. MORE Touch this pad to add ten seconds of cooking time each time you press it.

19. LESS Touch this pad to subtract ten seconds of cooking time each time you press it.

20. START/ENTER Touch this pad to start a function. If you open the door after oven begins to cook, touch START/ENTER again.

21. STOP/CLEAR Touch this pad to stop the oven or to clear all entries.

22. LIGHT HI/LOW/OFF Touch this pad to turn the light on high, low, or off.

23. VENT HI/LOW/OFF Touch this pad to turn the fan on high, low, or off.

24. VENT TURBO Touch this pad to choose the most powerful fan speed.

11. MELT Touch this pad to melt Butter / Magarine, Chocolate, Cheese, and Marshmallows.

12. COOK TIME Touch this pad to to set a cooking time.

25. VENT AUTO TIME SET Touch this pad when setting ventilation time. (1, 3, 5, 10, and 30 minutes.)

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5. WIRING DIAGRAM / KEY MATRIX

5-1. Wiring Diagram

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5-2. Key Matrix

KEY MATRIX

Hi / Low / OFF

(Vent On / Off)

56789101112913

1234 5678

CUSTOM

SET

VENT

SENSOR

POPCORN

TIME

COOK

TURBO

(Vent Speed)

SENSOR

COOK

POWER

LEVEL

LIGHT SOFTEN

SENSOR REHEAT

WARMING

(Hold Warm)

MAC &

CHEESE

DEFROST

(Auto Defrost)

T/T ABLE

ON/OFF

STOP / CLEAR

EZ-ON

(ADD30SEC)

Timer CLOCK NA

HOT DOG

ENTER /

START

MELT MORE

CHICKEN

NUGGETS

LESS

AUTO

Time Set

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6. TROUBLESHOOTING

6-1. General Information for Service

GENERAL PRECAUTIONS IN USE

A. Never operate the unit when it is empty.

Operating the oven with no load may shorten the life of the magnetron. Whenever cooking dry foods (dried fish, bread, etc.) or a small amount of food, be sure to put a glass of water into the cooking compartment. The glass turntable may become hot after operating, be careful when touching it.

B. Aluminum foil should be avoided because it will

disrupt cooking and may cause arcing. However, small pieces may be used to cover some parts of food to slow the cooking. Any aluminum foil used should never be closer than 2.5 cm to any side wall of the oven.

TRIAL OPERATION

After installation, the following sequences and results should be checked carefully.

A. Put a container filled with water (about 1 liter)into

the oven, and close the door tightly. B. Set cooking time for 10 minutes. C. Press the START pad to start.

Make sure the cavity light comes on. The unit will

begin cooking and the display window will show the

time counting down by seconds. D. After about 5 minutes, make sure the primary

interlock switch, the secondary interlock switch

and the interlock monitor switch operate properly

by opening and closing the door several times.

Press the Press the START pad each time the

door is closed. E. Continue operating the unit. For long beep sound

signal is heard when the time is up. The unit will

shut off automatically. F. Confirm the water is hot. G. Finally, measure the output power according to

POWER OUTPUT MEASUREMENT on page 27.

FEATURES AND SPECIFICATIONS FEATURES

A. The safety systems incorporated in this model

are: (1) Primary interlock switch (2) Secondary interlock switch (3) Interlock monitor switch (4) Choke system (5) Oven cavity thermostat

(Note: This thermostat located on the oven cavity will open and stop the unit from operation only if a high temperature is reached, such as, a fire created by overcooking food.)

B. Any one of 10 power output levels ranging 0 W to

1,100 W can be selected by the touch control and

electronic computer system.

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6-2. Safety Caution

A. SINCE NEARLY 4,000 VOLTS EXISTS IN

SOME CIRCUITS OF THIS UNIT REPAIRS SHOULD BECARRIED OUT WITH GREAT CARE.

The filament leads of magnetron carry High Voltage with respect to ground. Extreme caution must be exercised. Never plug the unit into a power source to determine which component is defective in high voltage section.

B. TO AVOID POSSIBLE EXPOSURE TO

MICROWAVE ENERGY LEAKAGE, THE FOLLOWING PRECAUTIONS MUST BE TAKEN BEFORE SERVICING.

(1) Before the power is applied:

(a) Make sure the primary interlock switch, the

secondary interlock switch and the interlock monitor switch operate properly by opening and closing the door several by opening and closing the door several times.

(b) Make sure the perforated screen and the

dielectric choke of the door are correctly and firmly mounted.

(2) After power is applied:

(a) Make sure the interlock switch mechanism

is operating properly by opening and closing the door.

(b)

Check microwave energy leakage must be below

the limit of 5 mW/cm2. (All service adjustments should be made for minimum microwave energy leakage readings).

(3) Do not operate the unit until it is completely

repaired, if any of the following conditions exist.

The unit must not be operated. (a) The door does not close firmly. (b) The hinge is broken. (c) The door seal is damaged. (d) The door is bent or warped, or there is any

other visible damage on the unit that may

cause microwave energy leakage. NOTE: Always keep the seal clean. (e) Make sure that there are no defective parts

in the interlock mechanism. (f) Make sure that there are no detective parts

in the microwave generating and

transmission assembly (especially

waveguide).

(4) The following items should be checked after the

unit is repaired:

(a) The interlock monitor switch is connected

correctly and firmly. (b) The magnetron gasket is properly positioned

and mounted. (c) The waveguide and the oven cavity are

intact.

(no microwave energy leakage) (d) The door can be properly closed and the

safety switches work properly. (e) The unit must stop when the door is opened

or the time is up.

The unit must not be operated with any of the above components removed or bypassed.

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6-3. Basic Check Summary

120V Ac

BK-CN1-3

WH-CN1-5

120 V Ac

BK-L

WH-N

Symptom : Dead

Check : Open/Short

Symptom: Dead

Check : Open/Short (It is normally recovered if the set is cooled down)

Symptom: Dead

Check :Open/Short

Symptom #1(Door is closed): No

cook, Operate F.M, S.M, T.T.M. automatically Check: Open/Short when the door is closed. (Switch) Symptom #2(Door is open): Not operate F.M, S.M, T.T.M. Check: Open/Short when the door is open. (Switch)

Symptom #1(Door is closed): No

key, Not start, Operating O.L, F.M, S.M, T.T.M. Check: Open/Short when the door is closed. (Switch) Symptom #2(Door is open): Not turn on O.L Check: Open/Short when the door is open. (Switch)

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6-4. Troubleshooting

No Display or Dead

-14-

Does the display operate?

When you push the any key, is there any beep sound

Power Off

Is the connector connected to PCB?

Yes

Go to No.8 of this flow chart.

Is there any beep sound in continuity test between the ends of thermostats? (Oven, Heater, Magnetron)

Oven Thermostat

Magnetron Thermostat

Replace the thermostats.

Is there any beep sound in continuity test between the power code and connector? Code “L” to Pin3 Code “N” to Pin5

Check PCB

Yes

Go to No.8 of this flow chart.

Heater Thermostat

Yes

NNN

LLL

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+ 35 hidden pages