LG MS-1146SQP Service Manual Download Page 25

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5-15

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 relay2.
(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 are in the 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 MS-1146SQP

Page 1: ...OVEN SERVICE MANUAL MODEL MS3042G CAUTION BEFORE SERVICING THE UNIT READ THE SAFETY PRECAUTIONS IN THIS MANUAL Website http biz lgservice com P NO MFL31039033 August 2012 Printed in Korea 삼 흥 정 판 Internal Use Only ...

Page 2: ...r 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...

Page 3: ...4 1 OPERATING SEQUENCE 4 2 SCHEMATIC DIAGRAM 4 3 CIRCUIT DESCRIPTION 4 4 SERVICE INFORMATION 5 1 TOOLS AND MEASURING INSTRUMENTS 5 1 MICROWAVE LEAKAGE TEST 5 1 MEASUREMENT OF MICROWAVE POWER OUTPUT 5 3 DISASSEMBLY AND ADJUSTMENT 5 3 INTERLOCK CONTINUITY TEST 5 7 COMPONENT TEST PROCEDURE 5 8 TROUBLE SHOOTING 5 11 EXPLODED VIEW 6 1 REPLACEMENT PARTS LIST 7 1 ...

Page 4: ...Control System Clock 1 00 12 59 Microwave Power for Variable Cooking Power level HIGH Full power throughout the cooking time 9 Saute approx 90 of Full power 8 Reheat approx 80 7 Med High approx 70 6 Medium approx 60 5 Med Low approx 50 4 Defrost approx 40 3 Low approx 30 2 Simmer approx 20 1 Warm approx 10 Owner s manual Glass turntable ITEM Model Power Requirement Power Output Microwave Frequency...

Page 5: ...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 2 1 CAUTIONS Unlike other appliances the microwave oven is high voltage and high current equipment Though it is free from...

Page 6: ...d 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 EARTHING INSTRUCTIONS This microwave oven is designed to be used in a fully earthed condition It is imperative therefore to make sure it is properly earthed before servicing WARNING THIS APPLIANCE MUST BE EARTHED IMPORTANT As the colors of the w...

Page 7: ... with weight pad 4 EXPRESS DEFROST Touch this pad to defrost foods quickly 5 BREAD DEFROST Touch this pad to defrost bread 6 CLOCK Used to set the time of day 7 POWER Used to select the desired power level for cooking 8 TIME Touch this pad to set a cook time 9 NUMBER Used to set for time of day cooking time power level or defrost weight 10 SOFTEN 11 MELT 12 STOP CLEAR Used to stop over and clear a...

Page 8: ... AUTO COOK 8 AUTO DEFROST 9 QUICK DEFROST COOKING 10 CHILD LOCK This oven has a CHILD LOCK feature TO SET CHILD LOCK Touch the pad Touch and hold DENTENER pad L appear on the display TO CANCEL CHILD LOCK Touch the pad Touch and hold DENTENER pad L disappears STOP CLEAR STOP CLEAR QUICK DEFROST STOP CLEAR TIME START NUMBER STOP CLEAR AUTO COOK START NUMBER STOP CLEAR CLOCK START NUMBER STOP CLEAR A...

Page 9: ...SCHEMATIC DIAGRAM 4 3 ...

Page 10: ...ximately 2100 volts AC is generated in the secondary of the high voltage transformer which is increased by the action of the high voltage diode and charging of the high voltage capacitor The negative 4 000 Volts DC is applied to the filament of the magnetron WHEN THE OVEN IS SET AT ANY LEVEL EXCEPT MAXIMUM The micom controller controls the ON OFF time of relay 2 by the applied signal to vary the a...

Page 11: ...nt openings for microwave leakage Check for microwave leakage after every servicing The power density of the microwave radiation leakage emitted by the microwave oven should not exceed 4 mW cm2 Always start measuring of an unknown field to assure safety for operating personnel from radiation leakage NECESSARY MEASURING INSTRUMENTS TESTER VOLTS DC AC Ohmmeter Microwave survey meter Holaday HI 1500 ...

Page 12: ...t probe must be removed no faster than 1 inch sec 2 5 cm sec along the shaded area otherwise a false reading may result The test probe must be held with the grip portion of the handle A false reading may result if the operator s hand is befween the handle and the probe When testing near a corner of the door keep the probe is moved perpendicular to the surface making sure the probe horizontally alo...

Page 13: ...l having a maximum material thickness of 3 mm and an outside diameter of approximately 190 mm The oven and the empty bowl are at ambient temperature prior to the start of the test The initial temperature T1 of the water is 10 2 C It is measured immediately before the water is added to the bowl After addition of the water to the bowl the load is immediately placed on the center of the turntable whi...

Page 14: ...ance between the door and the oven E HIGH VOLTAGE TRANSFORMER REMOVAL 1 Discharge the high voltage capacitor 2 Disconnect the leadwire from magnetron high voltage transformer and capacitor 3 Remove the screw holding the high voltage transformer to the baseplate F FAN MOTOR ASSEMBLY REMOVAL 1 Discharge the high voltage capacitor 2 Disconnect the leadwire from fan motor and high voltage capacitor 3 ...

Page 15: ...on To prevent microwave leakage tighten the mounting screws properly making sure there is no gap between the waveguide and the magnetron J REMOVING THE TURNTABLE MOTOR 1 Remove the turntable 2 Remove the turntable shaft VERY CAREFULLY with a slotted screwdriver 3 Lay the unit down on its back 4 Remove the turntable motor cover The turntable base cover is easily removed by pinching the six parts wi...

Page 16: ...ONITOR SECONDARY SWITCHES TO THE LATCH BOARD 3 INSTALLATION AND ADJUSTMENT OF THE LATCH BOARD TO THE OVEN ASSEMBLY Mount the latch board to the oven assembly Adjust the latch board in the arrow direction so that oven door will not have any play in it when the door is closed Tighten the mounting screw Check for play in the door by pushing the door release button Door movement should be less than 0 ...

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: ...OLTAGE TRANSFORMER Wire leads removed MAGNETRON Wire leads removed Approx 2 13 10 ohm Approx 178 19 10 ohm Less than 1 ohm Normal Infinite Normal Infinite Normal Less than 1 ohm Normal Infinite PRIMARY TERMINAL SECONDARY TERMINAL WINDING FILAMENT TERMINAL COMPONENTS TEST PROCEDURE RESULTS 1 Measure the resistance Ohm meter scale Rx1 and Rx100 Primary winding Secondary winding Filament winding 2 Me...

Page 19: ...ormal Momentarily indicates several ohms and then gradually returns to infinite Normal Infinite Normal Continuity Abnormal Infinite Normal Infinite Abnormal Continuity Measure the resistance Ohm meter scale Rx1000 Terminal to case Measure the continuity Forward Ohm meter scale Rx10000 Measure the continuity Reverse Ohm meter scale Rx10000 HIGH VOLTAGE DIODE NOTE Some inexpensive meters may indicat...

Page 20: ...NIT IS SERVICED FOR ANY REASON MAKE SURE THE WIRE LEADS ARE IN THE CORRECT POSITION WHEN REMOVING THE WIRE LEADS FROM THE PARTS BE SURE TO GRASP THE CONNECTOR NOT THE WIRES Relay 1 Relay 2 A RD B BK C WH Measure the resistance Ohm meter scale R x 1000 Normal A B Approx 65 80 ohm B C Approx 10 30 ohm A C Approx 85 105 ohm Abnormal Infinite or several ohm Normal Approx 100 150 ohm Abnormal Infinite ...

Page 21: ...tallic ware for cooking except where noted in the cooking guide Do not use any type of cookware with metallic trimming CAUSE REMEDY TROUBLE SHOOTING CAUTIONS 1 Check grounding before checking for trouble 2 Be careful of the high voltage circuit 3 Discharge the high voltage capacitor See page 2 1 4 When checking the continuity of the switches or of the high voltage transformer disconnect one lead w...

Page 22: ...ce key membrane assembly Defective PCB assembly Replace PCB assembly 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 t...

Page 23: ...ntinuity No continuity Malfunction of the monitor switch Replace fuse primary monitor secondary 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 secondary switches and RELAY RY2 of P C B Assembly Check continuity of primary switch with door opened Normal Replace f...

Page 24: ... 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 Defective PCB asse...

Page 25: ...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 Abno...

Page 26: ... 6 1 OVEN CAVITY PARTS INTERIOR PARTS BASE PLATE PARTS LATCH BOARD PARTS DOOR PARTS CONTROL PANEL PARTS EXPLODED VIEW INTRODUCTION EV MODEL Customer Model Product Code SVC Model ...

Page 27: ... 6 2 DOOR PARTS 14026A 14970A 13581A 13536A 13552A 13213A 13720D 14890A EV ...

Page 28: ... 6 3 CONTROLLER PARTS 24970A 250201 23572A 268711 24781M 24510L 23506A EV ...

Page 29: ... 6 4 OVEN CAVITY PARTS 33390G 35889A 33112U 36549S 33052A EV ...

Page 30: ... 6 5 LATCH BOARD PARTS 43501A 43500A 466001 466003 466001 WSZ085 EV ...

Page 31: ... 6 6 INTERIOR PARTS 56851D 568771 56930M 56411A 56324A WSZ002 50CZZH 54810C 56901A 55900A 56549F 54974S WSZ062 WSZ062 50FZZA 56201A 56912B WSZ002 55262A 34930W WSZ002 EV ...

Page 32: ... 6 7 BASE PLATE PARTS 63303A 56170D WSZ002 EV ...

Page 33: ......

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