LG LCRM1240SB Service Manual Download Page 29

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(TROUBLE 3) Display shows all figures set, but microwave oven does not start cooking while desired

program times are set and START pad is touched.

(TROUBLE 4) Microwave oven seems to be operating but little heat is produced in oven load.

1.Setting time

does not count
down when
touching START
pad.

2. Fan motor or

oven lamp do
not turn on.

No continuity.

Continuity.

Defective
secondary switch.

Replace
secondary switch.

Check continuity
of secondary
switch (with
door closed).

Check the con-
nection between
CN1 connector
and PCB
assembly.

Continuity

No continuity

Abnormal

Normal

Defective fan motor.

Defective oven lamp.

Defective PCB
assembly.

Loose connection.

Output is low.

Lower than 90% of
rating voltage.

Normal.

Decrease in power
source voltage
with load.

Suggest customer
contact local
electric power
utility co. or
qualified
electrician.

Check the
power source
voltage.

Disconnect the
wire leads from
relay 2 and
check on and off
time with
multitester.

Measure the
output power.

Abnormal.

Normal.

Defective PCB
assembly.

Defective
magnetron.

Replace PCB
assembly.

Replace
magnetron.

Replace PCB
assembly.

Connect them
tightly.

Replace fan motor.

Replace oven lamp.

Check fan motor.

Check oven lamp.

CONDITION

CHECK

RESULT

CAUSE

REMEDY

CONDITION

CHECK

RESULT

CAUSE

REMEDY

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.

Summary of Contents for LCRM1240SB

Page 1: ... OVEN SERVICE MANUAL MODEL LCRM1240SW LCRM1240SB LCRM1240ST CAUTION BEFORE SERVICING THE UNIT READ THE SAFETY PRECAUTIONS IN THIS MANUAL Website http us lgservice com P NO 3828W5S3848 July 2004 Printed in Korea ...

Page 2: ...ear 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 se...

Page 3: ...e 11 12 8 Disassembly Instructions 13 16 9 Interlock Continuity Test 17 10 Test and Checkout Procedures and Troubleshooting A Test Procedures 18 21 B Checkout Procedures 22 24 C Troubleshooting 25 30 11 Exploded View 31 39 12 Replacement Parts List 40 48 FOREWORD Read this Manual carefully Failure to adhere to or observe the information in this Manual may result in exposing yourself to the Microwa...

Page 4: ...D 14 11 16 W x 9 5 8 H x 15 5 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 COFFEE MAKER COMBI Owner s manual Glass turntable Roller rest ITEM MODEL Power Requirement Power Output Microwave F...

Page 5: ...per 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...

Page 6: ...al 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 al...

Page 7: ... 6 6 OVERALL CIRCUIT DIAGRAM A I SCHEMATIC DIAGRAM Check the Rating Model No ...

Page 8: ... 7 A II SCHEMATIC DIAGRAM Check the Rating Model No ADD Noise filter FUSE 20A ...

Page 9: ... 8 B MATRIX CIRCUIT FOR TOUCH KEY BOARD ...

Page 10: ...ck 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 coo...

Page 11: ...al 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...

Page 12: ... 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 1000 C B MEASURI...

Page 13: ...so 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 MEAS...

Page 14: ...AGE CIRCUIT A REMOVING OUT CASE Figures 7 1 Remove four screws from the rear section 2 Remove one screw from the side section 3 Push the outer case back about 1 inch 3cm 4 Lift the case from the set B REMOVING COFFEE MAKER ASSEMBLY Figure 8 CAUTION BE CAREFUL HOT SURFACE AFTER BREWING ENTIRE WARNING PLATE SURFACES ARE VERY HOT BEFORE SERVICING COOL DOWN THE COFFEE MAKER PARTS ENOUGH NOT TO GET BUR...

Page 15: ...ondary 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 5 mW cm sq 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 I...

Page 16: ...ed to the magnetron To prevent microwave leakage tighten the mounting screws properly making sure there is no gap between the waveguide and the magnetron E REMOVING THE TURNTABLE MOTOR Figure 11 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 Disc...

Page 17: ...move the high voltage diode earth screw I 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 2 MOUNTING OF THE PRIMARY MONITOR SECONDARY SWITCHES TO THE LATCH BOARD 3 INSTALLATION AND ADJUSTME...

Page 18: ...tion 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 c...

Page 19: ...H VOLTAGE TRANSFORMER Wire leads removed MAGNETRON Wire leads removed Approx 0 7 0 9 ohm Approx 90 120 ohm Less than 1 ohm Normal Infinite Normal Infinite Normal Less than 1 ohm Normal Infinite FILAMENT WINDING PRIMARY TERMINAL SECONDARY WINDING COMPONENTS TEST PROCEDURE RESULTS 1 Measure the resistance Select the ohm scale on the meter Primary winding Secondary winding Filament winding 2 Measure ...

Page 20: ...ts 2 Select the DCV scale on the meter 3 Using the meter battery and jump wire connect the items as illustrated in figures Terminal to terminal Normal Approximately 9V Normal Approximately 0V or a value displayed in mV Will be seen 1 Check DC 9V battery before performing tests 2 Select the DCV scale on the meter 3 Using the meter battery and jump wire connect the items as illustrated in figures Te...

Page 21: ...he items as illustrated in Figure 14 b This has the positive side of the battery connected to the cathode of the diode 3 The diode should be forward biased therefore a voltage reading of approximately 4 7 VDC to 6 4 VDC will be read depending on meter battery strength etc Note If the meter leads were reversed a negative voltage of the same amount would be seen STEP 3 Test the diode for reverse bia...

Page 22: ...S ARE IN THE CORRECT POSITION WHEN REMOVING THE WIRE LEADS FROM THE PARTS BE SURE TO GRASP THE CONNECTOR NOT THE WIRES 1 Remove wire leads 2 Measure resistance Normal A Approximately 95 120 ohms B Approximately 10 25 ohms Abnormal Infinite Normal Approx 2 5 3 5 Kohms Abnormal Infinite or several ohm POWER LEVEL 1 2 3 4 5 6 7 8 9 10 4 sec 6 sec 8 sec 10 sec 12 sec 14 sec 16 sec 18 sec 20 sec 22 sec...

Page 23: ...ADJUSTMENT PROCEDURES on page 3 when the primary interlock secondary interlock switches and or the interlock monitor switches are adjusted or replaced 22 PROBLEMS CAUSES Fuse blows immediately after the door is closed Improper operation of the primary interlock secondary interlock switches and or the interlock monitor switch Malfunction of the high voltage transformer the high voltage capacitor in...

Page 24: ...terlock switches Replace the micro switches Defective RELAY or poor connection of relay Replace RELAY or correct the connection YES NO NO YES GOOD PROBLEM A FAN motor turn on without touching START key when the door is closed Remove the mate connector of I O CON from the circuit board does the unit still operate Replace the circuit board NO NO YES GOOD PROBLEM B FAN motor turn on When the door is ...

Page 25: ...normal relay continuously operates 3 The buzzer does not sound or continues to sound 4 Some segments of one or more digits do not light up or they continue to light up or segments light when they should not 6 Wrong figures appear 7 The figures of all digits flicker 8 Some of the indicators do no light up 9 The clock does not keep time properly 24 NOTE A MICROWAVE ENERGY LEAKAGE TEST MUST ALWAYS BE...

Page 26: ...e for cooking except where noted in the cooking guide Do not use any type of cookware with metallic trimming CAUSE REMEDY C TROUBLE SHOOTING CAUTIONS 1 Check grounding and cool this unit before checking for trouble 2 Be careful of the high voltage circuit 3 Discharge the high voltage capacitor 4 When checking the continuity of the switches or of the high voltage transformer disconnect one lead wir...

Page 27: ...y 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 ...

Page 28: ...function of the monitor switch Replace fuse primary monitor switches and RELAY RY2 of P C B Assembly Check continuity of monitor switch with door closed Continuity No continuity Shorted contact at the primary switch Replace fuse primary monitor switches and RELAY RY2 of P C B Assembly Check continuity of primary switch with door opened Normal Replace fuse Fuse blows again Defective high voltage ca...

Page 29: ...ve oven lamp Defective PCB assembly Loose connection Output is low Lower than 90 of rating voltage Normal Decrease in power source voltage with load Suggest customer contact local electric power utility co or qualified electrician Check the power source voltage Disconnect the wire leads from relay 2 and check on and off time with multitester Measure the output power Abnormal Abnormal Normal Defect...

Page 30: ...uity relay 2 Operate the unit Defective PCB assembly Replace PCB assembly Replace high voltage transformer Defective high voltage capacitor Replace high voltage capacitor Abnormal Normal Check high vol tage transformer Abnormal Normal Check high vol tage capacitor Defective high voltage diode Replace high voltage diode Abnormal Normal Check high vol tage diode Defective magnetron Replace magnetron...

Page 31: ... No continuity Defective heater Defective PCB assembly 2 F 2 code Attached Seperated 2 wire leads are shorted contact Apart 2 wire leads as far as possible Check the CN3 connector whether 2 wire leads are attached Defective PCB assembly Replace PCB assembly Replace heater Defective thermostat Replace themostat Replace PCB Assembly Loose connection Connect them tightly CONDITION CHECK RESULT CAUSE ...

Page 32: ... 31 EXPLODED VIEW INTRODUCTION EV ...

Page 33: ... 32 DOOR PARTS 15006A 13581A 13552A 13536A 13213A 14890A 14026A 14970A WTP004 268711 13720D 13551A For model LCRM1240ST 13650A 23506A WTT028 EV ...

Page 34: ... 33 OVEN CAVITY PARTS 33052A 33112U WSZ185 WTT010 WTT047 33390G 35889A WTP013 36549S LCRM1240SB For model For model LCRM1240SW LCRM1240ST EV ...

Page 35: ... 34 LATCH BOARD PARTS WSZ085 56912B 55262A 466003 466001 466001 43500A EV ...

Page 36: ...2 55900A 268712 54974S 56549F 568772 WTT037 WSZ002 56411A WSZ002 35012A 34930W 55006F 50FZZA Check the Rating Model No Check the Rating Model No Check the Rating Model No Check the Rating Model No EV Model LCRM1240SW LCRM1240SB LCRM1240ST Check the rating label of Model and order SVC parts according to the Model No ...

Page 37: ...900A 268712 54974S 56549F 568772 WTT037 WSZ002 56411A WSZ002 35012A 34930W Check the Rating Model No Check the Rating Model No Check the Rating Model No Check the Rating Model No 50FZZA 56201A EV Model LCRM1240SW 01 LCRM1240SB 01 LCRM1240ST 01 Check the rating label of Model and order SVC parts according to the Model No ...

Page 38: ... 37 BASE PLATE PARTS 63302A WTT021 65006A 647781 WTT028 WTT021 WSZ002 56170D 63303A EV ...

Page 39: ... 38 SENSOR PARTS WTP004 56501A WTT021 54974T EV ...

Page 40: ...551A WTT028 85301A 85220V 849701 85300S 86322A 84839A WTP INZZW1A004B1EA 030 84838W 839202 83720E 83551F 83650A 83550A 83551B 83495A 85024A WTP018 83052M 86930V 84810Q WTP004 84980A WSZ002 WTT028 852001 84510L 85220P 849702 For model LCRM1240ST For model LCRM1240ST For model LCRM1240ST WTC004 For model LCRM1240ST EV ...

Page 41: ......

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