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LG MS-3237BL, Service Manual

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LG MS-3237BL Service Manual Download Page 22

5-12

CONDITION

CHECK 

RESULT 

CAUSE 

REMEDY

1. No input can be

programmed.

Continuity.

No continuity.

Defective PCB
assembly.

Replace PCB
assembly.

Check the conn-
ection between
membrane key
assembly and
PCB assembly.

Replace key
membrane
assembly and
check operation.

2. Some inputs

cannot be
programmed.

4. Random

programming
when touching
other pads.

5. Display is fixed

at some figure
and can not
accept any
input.

3. Display shows a

number or figure
different from one
touched.

Everything works
as specified.

Still have trouble.

Loose
connection.

Connect them
tightly.

Defective key
membrane
assembly.

Replace 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 the display are not lighting.
5. Display does not count down with time blinking or up with clock operation.
6.Display obviously jumps in time while counting down.
7.Display counts down too fast while cooking.
8.Each indicator light does not turn on after setting cooking cycle.
9.Display time of day does not reappear when cooking is finished.

10.Beep sound is not heard when correct key is touched.  

Summary of Contents for MS-3237BL

Page 1: ...ICROWAVE OVEN SERVICE MANUAL MODEL MS 3237BL CAUTION BEFORE SERVICING THE UNIT READ THE SAFETY PRECAUTIONS IN THIS MANUAL Website http biz lgservice com P NO MFL32514607 May 2007 Printed in Korea 삼 흥 정 판 ...

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: ...mm 14 0 kg approx 16 0 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 Owner s manual Glass tray Rotating rest ITEM MODEL Power Requirement Power Output Microwave Frequency Magnetron Timer Outside Dimensions Cavity Di...

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: ...sed to show time of day power level of cooking cooking category 2 CLOCK Used to set the time of day 3 QUICK DEFROST Used to defrost quickly 4 POWER Used to select power level for cooking 5 TIMER To select convection temperature change cooking time and weight 6 START QUICK START One tap allows over to begin functioning 7 STOP CLEAR Used to stop over and clear all entries except time of day ...

Page 8: ...entry or a function currently in use The display will either return to the last item entered or to the clock 3 CHILD LOCK This oven has a CHILD LOCK feature TO SET CHILD LOCK Touch the Stop pad Touch STOP pad L appear in the display TO CANCEL CHILD LOCK Touch the Stop pad Touch STOP pad L disappears 4 QUICK START 5 MICROWAVE COOKING 6 AUTO WEIGHT DEFROST Stop Clock Clock Set the hour Set the minut...

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: ...e test 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 perpendicular to the surface making sure the probe horizontally along t...

Page 13: ...er of approximately 190 mm The oven and the empty vessel 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 vessel After addition of the water to the vessel the load is immediately placed on the center of the turntable which is in the lowest position and the microwave power switched...

Page 14: ...en 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 Remove the two screws holding th...

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: ...ARY MONITOR 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 th...

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: ...VOLTAGE TRANSFORMER Wire leads removed MAGNETRON Wire leads removed Approx 0 3 0 8 ohm Approx 100 200 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 Mea...

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: ...T 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 or several ohm POWER LEVEL 1 2 3 4 5 6 7 8 9 10 4 sec 6 sec 8 sec 10 sec ...

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: ...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 26: ...DOOR PARTS LATCH BOARD PARTS CONTROL PANEL PARTS INTERIOR PARTS BASE PLATE PARTS OVEN CAVITY PARTS 6 1 EXPLODED VIEW INTRODUCTION EV MODEL MS 3237BL ...

Page 27: ...6 2 DOOR PARTS 13552A 13213A 14026A 14970A 13581A 13536A WTT028 13650A 13720D 14890A EV ...

Page 28: ...6 3 CONTROLLER PARTS 268711 WTP004 24781S 23572A 25020M 25020S WTP013 268712 24940T 24940P 23806C EV ...

Page 29: ...6 4 OVEN CAVITY PARTS 35889A 36549S 33390G 33112U WTP013 WTT010 33052A EV ...

Page 30: ...6 5 LATCH BOARD PARTS 466003 466001 43501A 43500A 466001 WSZ085 44510A EV ...

Page 31: ...6 6 INTERIOR PARTS 56930V 34930W WSZ002 568771 WSZ062 56411A 50FZZA 56549F 56201A WTT028 WSZ002 54974S WTT037 55900A 50CZZH WSZ002 WTT028 54810C WSZ002 56912B 55262A 948501 56324A WSZ002 56851D EV ...

Page 32: ...6 7 BASE PLATE PARTS 56170D 63302A EV ...

Page 33: ......

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