Lg Lcrm1240sw, Lcrm1240st, Lcrm1240sb Service Manual

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MICROWAVE OVEN

SERVICE MANUAL

MODEL: LCRM1240SW

CAUTION

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

P/NO : 3828W5S3848

LCRM1240SB
LCRM1240ST

July, 2004

Printed in Korea

SAFETY PRECAUTIONS

This device is to be serviced only by properly qualified service personnel.
Consult the service manual for proper service procedures to assure continued safety operation and for precautions to be taken to
avoid possible exposure to excessive microwave energy.

PRECAUTIONS TO BE OBSERVED BEFORE AND DURING
SERVICING TO AVOID POSSIBLE EXPOSURE TO
EXCESSIVE MICROWAVE ENERGY

A) Do not operate or allow the oven to be operated with the door open.

B) Make the following safety checks on all ovens to be serviced before activating the magnetron or other

microwave source, and make repairs as necessary; (1) interlock operation, (2) proper door closing, (3) seal

and sealing surfaces (arcing, wear, and other damage), (4) damage to or loosening of hinges and latches, (5)

evidence of dropping or abuse.

C) Before turning on microwave power for any service test or inspection within the microwave generating

compartments, check the magnetron, wave guide or transmission line, and cavity for proper alignment,

integrity, and connections.

D) Any defective or misadjusted components in the interlock, monitor, door seal, and microwave generation and

transmission systems shall be repaired, replaced, or adjusted by procedures described in this manual before

the oven is released to the owner.

E) A microwave leakage check to verify compliance with the Federal Performance Standard should be performed

on each oven prior to release to the owner.

CAUTION

MICROWAVE RADIATION

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

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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.

MECHANICAL SERVICE INFORMATION

TABLE OF CONTENTS

1. Safety precautions

2. Specifications

3. Cautions

4. Installations

5. Overall Circuit Diagram

6. Operating Procedures

7. Procedure for Measuring Microwave Energy Leakage

8. Disassembly Instructions ............................................................................................................................ 13-16

9. Interlock Continuity Test ............................................................................................................................. 17

10. Test and Checkout Procedures,and Troubleshooting

A. Test Procedures

B. Checkout Procedures

C. Troubleshooting

11. Exploded View

12. Replacement Parts List

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Inside front cover

3

4

5

6-8

9-10

11-12

18-21

22-24

25-30

31-39

40-48

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SPECIFICATIONS

Back Side

ITEM

MODEL

Power Requirement

Power Output

Microwave Frequency

Magnetron

Timer

Outside Dimensions

Cavity Dimensions

Net Weight

Shipping weight

DESCRIPTION

LCRM1240SW

LCRM1240SB

LCRM1240ST

120 Volts AC 60 Hz (13.8A - MWO, 14.5A - Combo)

Single phase, 3 wire grounded

Microwave 1650W

Coffee Maker 750W / 90W

1200 Watts full microwave power (IEC60705)

2450 MHz

2M246 - 050GF

0 ~ 59 sec. ,0 ~ 99 min.

23”(W)x 12 1/2 ”(H)x 17 1/8 ”(D)

14 11/

16 ”(W)x 9

15.9 kg (approx.)

17.3 kg (approx.)

5

/

8 ”(H)x 15

5

/

8 ”(D)

Control Complement

Nameplate Location

Accessories

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

COFFEE MAKER, COMBI

Owner's manual

Glass turntable

Roller rest

This microwave oven is designed for household use only.

It is not recommended for commercial purposes.

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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

•

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.

COOLING FIN

FILAMENT
TERMINALS

MAGNETRON
CHASSIS GROUND

MAGNETRON

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

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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).

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

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.

10cm

TEMPORARY METHOD
(ADAPTER PLUGS NOT
PERMITTED IN CANADA)

ALIGN LARGE
PRONGS/SLOTS

ENSURE PROPER GROUND
AND FIRM CONNECTION
BEFORE USE

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6. OVERALL CIRCUIT DIAGRAM
A (I). SCHEMATIC DIAGRAM *Check the Rating Model No.

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A (II). SCHEMATIC DIAGRAM *Check the Rating Model No. (ADD Noise filter)

FUSE 20A

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B. MATRIX CIRCUIT FOR TOUCH KEY BOARD

-8-

7. OPERATING PROCEDURES

1

12

3

4

6

8

10

2

13

5

7

9 11

1 3 5

2 64

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. (microwave oven only)

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 programmed food items.

5. EZ-ON. Touch this pad to cook at 100% cooking 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. EZ DEFROST. This pad provides you with the quick defrosting method for 1.0 pound of frozen foods.

8. CUSTOM SET. Touch this pad to change the oven's default settings for clock, sound, 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 the cooking time.

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

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

13. SENSOR TOUCH. This pad allows you to cook most of your favorite foods without having to select

cooking times and power levels.

COFFEE MAKER CONTROL AREA

1. 1-4. This pad is small batch function. This pad is used when you want to brew a small amount (1~4 cups) of coffee.

2. TEMP. This pad is used when you want to adjust the warming plate temperature of the coffee.

3. OFF/CLEAR. Touch this pad to stop the coffee maker or clear entries. (coffee maker only)

4. ON. This pad is used when you want to brew more than 4 cups of coffee.

5. TIME SET. Touch this pad to change the default setting of the coffee maker for brew timer or warming plate timer.

6. TIMER ON/OFF. This pad is used when you want to turn the brew timer function On or Off.

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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.

COFFEE MAKER

(1) BREW

1. Touch BREW.

(2) Small Batch

1. Touch 1-4.

(3) TIME SET.

1. Time of the day.

2. Touch TIME SET.

3. Touch 1 Auto-on time or Touch 2 warm time.

4. Setting Auto-on time.

5. Touch TIME SET.

6. Touch 1 for A.M.or Touch 2 for P.M.

7. Touch TIME SET.

8. Touch 1 for brew or Touch 2 for small batch.

9. Touch TIME SET.

(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.

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8. PROCEDURE FOR MEASURING MICROWAVE

Figure 6

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.

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:

Temperature Rise

Line Voltage Degrees °F Degrees °C

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

(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.

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.

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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