LG LTRM1240xx Service Manual

MICROWAVE OVEN

SERVICE MANUAL

MODEL: LTRM1240SW

LTRM1240SB LTRM1240ST

CAUTION

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

Website http://us.lgservice.com

P/NO : 3828W5S6018

July, 2004

Printed in Korea

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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.

SAFETY PRECAUTIONS

CAUTION

MICROWAVE RADIATION

DO NOT BECOME EXPOSED TO RADIATION FROM THE MICROWAVE GENERATOR OR OTHER PARTS CONDUCTING MICROWAVE ENERGY.

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MECHANICAL SERVICE INFORMATION

TABLE OF CONTENTS

1. Safety precautions

......................................................................................................................................

Inside front cover

2. Specifications

..............................................................................................................................................

3. Cautions

......................................................................................................................................................

4. Installations

.................................................................................................................................................

5. Overall Circuit Diagram

...............................................................................................................................

6-7

6. Operating Procedures

.................................................................................................................................

8-9

7. Procedure for Measuring Microwave Energy Leakage

..............................................................................

10-11

8. Disassembly Instructions ............................................................................................................................ 12-15

9. Interlock Continuity Test ............................................................................................................................. 16

10. Test and Checkout Procedures,and Troubleshooting

A. Test Procedures

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17-20

B. Checkout Procedures

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21-23

C. Troubleshooting

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24-29

11. Exploded View

..........................................................................................................................................

30-37

12. Replacement Parts List

.............................................................................................................................

38-44

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.

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This microwave oven is designed for household use only.

It is not recommended for commercial purposes.

DESCRIPTION

LTRM1240SW

LTRM1240SB

LTRM1240ST

120 Volts AC 60 Hz

Single phase, 3 wire grounded

Microwave 1650W

Toast 800W

1200 Watts full microwave power (IEC60705)

2450 MHz

2M214

0 ~ 90 min.

23”(W)x 12 1/2 ”(H)x 17 1/8 ”(D)

14 11/

16 ”(W)x 9

8 ”(H)x 15

8 ”(D)

15.9 kg (approx.)

17.3 kg (approx.)

Microwave Power for Variable Cooking

Power level

MAX ...................................... Full power throughout the cooking time

MED.-HIGH ............................ approx. 80% of Full power

MEDIUM ................................ approx. 60% of Full power

DEFROST .............................. approx. 40% of Full power

LOW/WARM ........................... approx. 20% of Full power

TOAST, COMBI

Owner's manual

Glass turntable

Roller rest

ITEM

MODEL

Power Requirement

Power Output

Microwave Frequency

Magnetron

Timer

Outside Dimensions

Cavity Dimensions

Net Weight

Shipping weight

Control Complement

Nameplate Location

Accessories

SPECIFICATIONS

Back Side

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• 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.

•

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.

• 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.

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.

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

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.

Gasket

ANTENNA

COOLING FIN

MAGNETRON CHASSIS GROUND

FILAMENT TERMINALS

MAGNETRON

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INSTALLATIONS

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.

BEFORE YOU BEGIN, READ THE FOLLOWING INSTRUCTIONS COMPLETELY AND CAREFULLY.

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

ENSURE PROPER GROUND AND FIRM CONNECTION BEFORE USE

10cm

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6. OVERALL CIRCUIT DIAGRAM A. SCHEMATIC DIAGRAM

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F U N AM

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DNA STNENOPMOC FO SEULAV EHT ,MARGAID CITAMEHCS CISAB SI SIHT ECNIS :ECITON

.TNEMEVORPMI ROF EGNAHC OT TCEJBUS

E RA SNOITCENNOC LAITRAP EMOS

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B. MATRIX CIRCUIT FOR TOUCH KEY BOARD

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7. OPERATING PROCEDURES A. OVEN CONTROL PANEL

MICROWAVE CONTROL AREA

1. DISPLAY. The Display includes a clock and indicators that tell you time of day, cooking time settings, and cooking

functions selected.

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

3. START. Touch this pad to start all entries (except the Auto Cook and Add Minute function which start automatically)

and to turn Child Lock on or off.

4. AUTO COOK. Touch this pad to select programming food items.

5. EZ-ON. Touch this pad to cook at 100% cook power for 1 minute to 99 minutes 59 seconds.

6. AUTO DEFROST. This pad is an accurate defrosting method for frozen meat, poultry and fish up to 6.0 lbs.

7. Q-DEFROST. This pad provides you with the quick defrosting method for 1.0 pound frozen foods.

8. CUSTOM SET. Touch this pad to change the oven's default settings for sound, clock, scroll speed and Lbs/Kg.

9. KITCHEN TIMER. Touch this pad to use your microwave oven as a kitchen timer.

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

11. POWER. Touch this pad to set a cooking power.

12. NUMBER PADS. Touch Number Pads to enter cooking time, power level, quantities, or weights.

13. SENSORTOUCH. This pad allows you to cook most of your favorite foods without having to select cooking times and

power levels.

TOASTER CONTROL AREA

1. Toast. Toast bread

2. Bagel. Toasts Bagels

3. Off/Clear. Touch this pad to stop the toaster or clear entries.

4. On. Touch this pad to start the toasting process.

5. Darkness Control. Adjust darkness control to desired setting before cooking foods.

(Default : 5, "1" is the lightest and "9" is the darkest)

6. Indicator Light. When operating toaster with door closed, this will be illuminated. If you open the door during toasting, this will blink.

24 6 8 10

13 5 7 9 11 1 12 3

B. EASY USE TABLE

MICROWAVE OVEN

(1) KITCHEN TIMER

1. Touch STOP/CLEAR.

2. Touch KITCHEN TIMER.

3. Touch correct number for time.

4. Touch START.

(2) CHILD LOCK

To set:

1. Touch STOP/CLEAR.

2. Touch “START” more than 4 seconds. To cancel:

1. Touch STOP/CLEAR.

2. Touch “START” more than 4 seconds.

(3) AUTO COOK

1. Touch STOP/CLEAR.

2. Touch AUTO COOK Category.

3. Touch START. (Although you don’t touch start, it will start after 4 seconds automatically)

(4) EZ-ON

1. Touch STOP/CLEAR.

2. Touch EZ-ON

(5) AUTO DEFROST

1. Touch STOP/CLEAR.

2. Touch AUTO DEFROST. Three different defrosting levels are provided.

(Touch 1 : Meat

Touch 2 : Poultry Touch 3 : Fish)

3. Enter the weight of your food in decimal increments from 0.1 to 6.0 pounds.

4. Touch START

5. At beeping, turn food over by following the instructions in the manual.

6. After turning food over, touch START to resume defrosting.

(6) TIMED COOKING

1. Touch STOP/CLEAR.

2. Touch COOK TIME.

3. Touch number for cooking time.

4. Touch POWER.

5. Touch number for cooking power level.

6. Touch START.

(7) MULTI-STAGE COOKING

1. Touch STOP/CLEAR.

2. Touch COOK TIME.

3. Touch number for cooking time.

4. Touch POWER.

5. Touch number for cooking power level.

6. Repeat steps 2-5 to set 2nd cooking stage.

7. Touch START.

TOASTER

(1) TOAST

1. Touch STOP/CLEAR.

2. Touch TOAST.

3. Touch Darkness Control (1~9 step)

4. Touch START.

(2) BAGEL

1. Touch STOP/CLEAR.

2. Touch BAGEL.

3. Touch Darkness Control (1~9 step)

4. Touch START.

(3) DARKNESS SETTINGS

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Degree of darkness Select darkness level

Light 1~3

Medium 4~6

Dark 7~9

8. PROCEDURE FOR MEASURING MICROWAVE ENERGY LEAKAGE

A. CAUTIONS

(1) Be sure to check a microwave emission prior to servicing

the oven if the oven is operative prior to servicing.

(2) The service personnel should inform the manufacturer,

importer, or assembler of any certified oven unit found to have a microwave emission level in excess of 5mW/cm.sq. 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.

(3) If the oven operates with the door open, the service

personnel should;

- Tell the user not to operate the oven

- Contact the manufacturer and CDRH (Center for Devices and Radiological Health) immediately. NOTE: Address on CDRH Office of Compliance (HFZ-312) Center for Devices and Radiological Health 1390 Piccard Drive Rockville, Maryland 20850

(4) The service personnel should check all surface and vent

openings for microwave emission testing.

(5) Check for microwave energy leakage after every

servicing. The power density of the microwave radiation leakage emitted by the microwave oven should not exceed 1mW/cm.sq. And always start measuring of an unknown field to assure safety for operating personnel from radiation leakage. NOTE: The standard is 5mW/cm.sq. while in the customer’s home. 1mW/cm.sq. stated here is manufacturer’s own voluntary standard for units in customer’s home.

EQUIPMENT

• Electromagnetic energy leakage monitor (NARDA 8100B, HOLADAY HI 1501)

• 600cc glass beaker

• Glass thermometer 1000C

B. MEASURING MICROWAVE ENERGY LEAKAGE

(1) Pour 275±15cc of 20±5 °C water in a beaker which is

graduated to 600 cc, and place the beaker in the center of the oven.

(2) Set the energy leakage monitor to 2450 MHz and use it

following the manufacturer’s recommended test procedure to assure correct result.

(3) When measuring the leakage, always use the 2 inch

(5cm) spacer supplied with the probe. (4) Operate the oven at its maximum output. (5) Measure the microwave radiation using and

electromagnetic radiation monitor by holding the probe

perpendicular to the surface being measured. (See

Figure 6)

Move probe along shaded area.

Probe scanning speed less than 2.5 cm/sec.

C. MEASUREMENT WITH THE OUTER CASE REMOVED

(1) 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.

- Around the magnetron

- The waveguide

WARNING: AVOID CONTACTING ANY HIGH VOLTAGE

PARTS.

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D. MEASUREMENT WITH A FULLY ASSEMBLED OVEN

(1) After all components, including the outer panels, are

fully assembled, measure for microwave energy leakage around the door viewing window, the exhaust opening and air inlet openings.

(2) Microwave energy leakage must not exceed the values

prescribed below.

NOTES:

Leakage with the outer panels removed - less than 5mW/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 1 mW/cm .sq.

E. NOTE WHEN MEASURING

(1) Do not exceed meter full scale deflection. (2) The test probe must be removed no faster than 1

inch/sec (2.5cm/sec) along the shaded area, otherwise a false reading may result.

(3) 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.

(4) 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 possibly cause probe damage.

F. RECORD KEEPING AND NOTIFICATION AFTER

MEASUREMENT

(1) 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.

(2) Should the microwave energy leakage not be more

than 1mW/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.

(3) At least once a year, have the electromagnetic energy

leakage monitor checked for calibration by its manufacturer.

G. POWER OUTPUT MEASUREMENT

(1) Fill the test beaker with 59 °F(15 °C) ~ 75 °F(24 °C) 1 liter tap

water.

(2) Stir the water in the beaker with thermometer (°F or °C) and

measure temperature as T1. (3) Place the beaker on the center of turntable. (4) Set for one (1) minute and three (3) seconds and operate

the oven at high power. NOTE: The additional three (3) seconds is to allow the

magnetron to begin generating power.

(5) When the heating is finished, stir the water again with

thermometer and measure the temperature of water as T2. (6) Subtract T1 from T2, this will give you the temperature rise. (7) The microwave power output is within specification, if the

temperature rise is as shown below:

(8) Power output will be influenced by line voltage of power

supply. Consequently, correct power output must be

measured within 120V AC ± 1 Volt while unit is operating.

SPECIAL TIP

• This oven used the button head screws.

• When you remove the screws, using the

tamper-resistant Torx driver have a

pin-in-head.

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Line Voltage Degrees °F Degrees °C

120 V 17.1 ~ 22.5 9.5 ~ 12.5 108 V Min. 12.6 Min. 7.0

Temperature Rise

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