LG LTRM1240SB Service Manual Download

Page: 29 / 39

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CONDITION

CHECK

RESULT

CAUSE

REMEDY

(TROUBLE 5) No microwave oscillation even though oven lamp and fan motor run.

(Display operates properly)

No microwave
oscillation.

No continuity.

Continuity.

Disconnect the
wire leads from
relay 2 and
check continuity
of relay 2.
(Operate the unit)

Defective PCB
assembly

Defective high
voltage
transformer.

Replace PCB
assembly

Output is full power
when you set lower
power level.

Abnormal.

Disconnect the
wire leads from
relay 2 and check
continuity 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.

Abnormal

Check
magnetron.

NOTE: • Make sure the wire leads correct position.

• When Removing the wire leads from the parts, be sure to grasp the connector, not the wires.
• When removing the magnetron, be sure to install the magnetron gasket in the correct position

and in good condition.

Summary of Contents for LTRM1240SB

Page 1: ... 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 ...

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: ... 10 11 8 Disassembly Instructions 12 15 9 Interlock Continuity Test 16 10 Test and Checkout Procedures and Troubleshooting A Test Procedures 17 20 B Checkout Procedures 21 23 C Troubleshooting 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 Microwav...

Page 4: ... 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 TOAST COMBI Owner s manual Glass turntable Roller rest ITEM MODEL Power Requirement Power Output Microwave Frequency Magnetron Timer Ou...

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: ...O F T N A T R O P M I A P D E I F I C E P S S R E R U T C A F U N A M Y L N O T A H T L A I T N E S S E S I T I G N I C I V R E S N E H W S D R A Z A H S T R G A I D C I T A M E H C S E H T F O S A E R A D E D A H S E H T N I S T N E N O P M O C L A C I T I R C E H T R O F D E S U E B M A R D N A S T N E N O P M O C F O S E U L A V E H T M A R G A I D C I T A M E H C S C I S A B S I S I H T E C N ...

Page 8: ... 7 B MATRIX CIRCUIT FOR TOUCH KEY BOARD ...

Page 9: ...OM 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...

Page 10: ...r 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 CO...

Page 11: ...d 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 1000 C B ME...

Page 12: ...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 13: ...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 TOASTING ENTIRE TOASTER S SURFACES ARE VERY HOT BEFORE SERVICING COOL DOWN THE TOASTER PARTS ENOUGH NOT TO GET BURNT 1 Ope...

Page 14: ...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 15: ...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 16: ...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 17: ...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 18: ...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 19: ...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 20: ...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 21: ...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 22: ...ADJUSTMENT PROCEDURES on page 3 when the primary interlock secondary interlock switches and or the interlock monitor switches are adjusted or replaced 21 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 23: ...ce 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 and indicator light 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 and indicator light turn on...

Page 24: ...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 23 NOTE A MICROWAVE ENERGY LEAKAGE TEST MUST ALWAYS BE...

Page 25: ...oking 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 wire from t...

Page 26: ...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 27: ...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 28: ...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 29: ...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 30: ...ontinuity No continuity Defective heater Defective PCB assembly 2 F 2 code Attached Seperated 2 wire leads are shorted contact Internal temperature is over 220 deg c Apart 2 wire leads as far as possible Check the CN3 connector whether 2 wire leads are attached 3 HOT code Allow the toaster to cool down Automatically fan will blow for 3 minutes to cool this unit Defective PCB assembly Replace PCB a...

Page 31: ... 30 EXPLODED VIEW INTRODUCTION ...

Page 32: ... 31 DOOR PARTS 14890A 13213A 13536A 13552A 15006A 13581A 14026A 14970A WTP004 268712 13720D 13650A 13551A For model LTRM1240ST 23506A For model LTRM1240SB LTRM1240SW WTT028 ...

Page 33: ... 32 OVEN CAVITY PARTS 33112U WTT010 WTT020 33390G 35889A WTP013 36549S 33052A WSZ185 LTRM1240SB LTRM1240ST For model For model LTRM1240SW ...

Page 34: ... 33 LATCH BOARD PARTS WSZ085 56912B 55262A 466003 466001 466001 43500A 44510A ...

Page 35: ... 34 OVEN INTERIOR PARTS 568771 56930V WTT028 56324A WSZ002 WTT028 56851D WSZ002 54810C 50CZZH WSZ002 55900A 54974S 56549F 568772 WTT037 WSZ002 56411A WTT024 34930W 35012A 55006F 50FZZA WSZ002 268711 ...

Page 36: ... 35 BASE PLATE PARTS 63302A WTT021 65006A 647781 WTT028 WTT021 WSZ002 56170D 63303A ...

Page 37: ... 36 SENSOR PARTS WTP004 56501A WTT021 54974T ...

Page 38: ... 37 COFFEE MAKER PARTS 75993M 73550L 768711 74970A 73650A 73551B 73720D 73213A 73552A 73572A 73740A 73551C 73551A 766001 74510L 76322A 76930V For LTRM1240ST For LTRM1240ST ...

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