LG MS-2072A Service Manual Download Page 25 | Manualshive

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5-15

CONDITION

CHECK

RESULT

CAUSE

REMEDY

No microwave
oscillation.

No continuity.

Continuity.

Abnormal

Defective high
voltage
transformer.

Replace high
voltage
transformer.

Normal

Defective PCB
assembly.

Replace PCB
assembly.

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

Check high vol-
tage transformer.

Abnormal

Defective circuit
protector.

Replace circuit
protector.

Normal

Check circuit
protector.

Abnormal

Defective high
voltage capacitor.

Replace high
voltage capacitor.

Normal

Check high vol-
tage capacitor.

Abnormal

Defective high
voltage diode.

Replace high
voltage diode.

Normal

Check high vol-
tage diode.

Abnormal

Defective
magnetron.

Replace
magnetron.

Check
magnetron.

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

(Display operates properly)

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Summary of Contents for MS-2072A

Page 1: ...MICROWAVE OVEN SERVICE MANUAL MODEL MS 2072A CAUTION BEFORE SERVICING THE UNIT READ THE SAFETY PRECAUTIONS IN THIS MANUAL ...

Page 2: ...nd 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 t...

Page 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 SCHEMATIC DIAGRAM OF P C B 8 1 PRINTED CIRCUIT BOARD 8 2 P C B PARTS LIST 9 1 CONTENTS ...

Page 4: ...ON MS 2072A 230 Volts AC 50 Hz 1 200 Watts Single phase 3 wire grounded 800 Watts full microwave power IEC 60705 2 450 MHz 2M214 39F 90 min 485 W x 280 H x 386 D mm 312 W x 198 H x 316 D mm 12 5 kg approx 14 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 ...

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 fro...

Page 6: ...lat 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 wire...

Page 7: ...e MORE LESS Used to increase or decrease the cooking time WEIGHT Used to select the weight of food 5 RUSSIAN COOK Used to cook the foods listed by one touch 6 STOP CLEAR Used to stop over and clear all entries except time of day 7 START QUICK START One tap allows over to begin functioning 4 1 OPERATING INSTRUCTIONS Oven Front Plate Control Panel Turntable Rotating Ring Safety Door Lock System Door...

Page 8: ...AVE COOKING 5 AUTO DEFROST COOKING 6 QUICK DEFROST COOKING 7 CHILD LOCK This oven has a CHILD LOCK feature TO SET CHILD LOCK Press the pad for 4 seconds L appear on the display TO CANCEL CHILD LOCK Press the pad for 4 seconds L disappears on the display 8 RUSSIAN COOK STOP CLEAR START quick start STOP CLEAR STOP CLEAR AUTO DEFROST SELECT THE WEIGHT START STOP CLEAR QUICK DEFROST STOP CLEAR POWER T...

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: ...ity of the microwave radiation leakage emitted by the microwave oven should not exceed 5 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 HI 1501 Narda 8100 8200 Inch scale 600 cc non conductive material beaker glass or plastic inside d...

Page 12: ...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 between 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 the oven surface this may possibly cause...

Page 13: ... 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 on The time T for the temperature of t...

Page 14: ...AL 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 noise filter and high voltage capacitor 3 Remove the two screws holding the the suction guide AS...

Page 15: ... 275 ml water load Make sure that gasket is rigidly attached to the magnetron To prevent microwave leakage tighten the mounting screws properly making sure there is no gap between the waveguide and the magnetron L REMOVING THE TURNTABLE MOTOR 1 Remove the turntable 2 Remove the turntable shaft VERY CAREFULLY 3 Lay the unit down on its back 4 Remove the turntable motor cover The turntable base cove...

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: ... 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 circuit in the door op...

Page 18: ... TEST PROCEDURE RESULTS HIGH VOLTAGE TRANSFORMER Wire leads removed MAGNETRON Wire leads removed 1 Measure the resistance Ohm meter scale Rx1 Primary winding Secondary winding Filament winding 2 Measure the resistance Ohm meter scale Rx1000 Primary winding to ground Filament winding to ground 1 Measure the resistance Ohm meter scale Rx1 Between Filament terminal 2 Measure the resistance Ohm meter ...

Page 19: ...le Rx1000 Terminal to case Measure the continuity Forward Ohm meter scale Rx10000 Measure the continuity Reverse Ohm meter scale Rx10000 Normal Momentarily indicates several ohms and then gradually returns to infinite Normal Normal Continuity Abnormal Normal Abnormal Continuity NOTE When testing the magnetron be sure to install the magnetron gasket in the correct position and be sure that the gask...

Page 20: ...cale R x 1000 POWER LEVEL 20 6 sec 16 sec 40 10 sec 12 sec 60 14 sec 8 sec 80 18 sec 4 sec 100 22 sec 0 sec Normal 350 450 Ω Abnormal or several Ω Normal 70 130 Ω Abnormal or several Ω NOTE A MICROWAVE LEAKAGE TEST MUST ALWAYS BE PERFORMED WHEN THE UNIT 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 C...

Page 21: ...static charge built up in your body Micom model only CONDITION Microwave oven does not work Inserting many plug into one plug outlet and using them at the same time blown fuse or breaker Microwave oven plug is not inserted tightly Output power is too low Low AC input voltage Food temperature is too low Using metallic ware and allowing it to touch the oven wall Sparks occur Inconsistent intensity o...

Page 22: ...ing cooking cycle 11 Display time of day does not reappear when cooking is finished 12 Beep sound is not heard when correct key is touched 5 12 TROUBLE 1 The following visual conditions indicate a probable defective control circuit CONDITION CHECK RESULT CAUSE REMEDY 1 No input can be programmed Continuity No continuity Defective PCB assembly Loose connection Replace PCB assembly Connect them tigh...

Page 23: ...f P C B Assembly Check continuity of monitor switch with door closed Check continuity of primary switch with door opened Disconnect one side of the wire lead connected from transformer to the high voltage capacitor and operate the unit Replace fuse 2 Fuse does not blow No continuity Continuity No continuity Defective power supply cord Replace power supply cord Defective thermostat Replace thermost...

Page 24: ...ws all figures set but oven does not start cooking while desired program times are set and START pad is touched TROUBLE 4 Oven seems to be operating but little heat is produced in oven load 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 CONDITION CHECK RESULT CAUSE REMEDY Output is low Lower than 90 ...

Page 25: ... unit Check high vol tage transformer Abnormal Defective circuit protector Replace circuit protector Normal Check circuit protector Abnormal Defective high voltage capacitor Replace high voltage capacitor Normal Check high vol tage capacitor Abnormal Defective high voltage diode Replace high voltage diode Normal Check high vol tage diode Abnormal Defective magnetron Replace magnetron Check magnetr...

Page 26: ...unit 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 CONDITION CHECK RESULT CAUSE REMEDY TROUBLE 5 No microwave oscillation even though oven lamp and fan motor run Display operates properly ...

Page 27: ...DOOR PARTS LATCH BOARD PARTS CONTROL PANEL PARTS INTERIOR PARTS BASE PLATE PARTS OVEN CAVITY PARTS 6 1 EXPLODED VIEW INTRODUCTION ...

Page 28: ...6 2 13581A 14970A 14026A 13552A 13213A 13352A 13720D 13650A WTP027 DOOR PARTS ...

Page 29: ...6 3 23572A 243501 23790D 243502 249401 250202 250201 24781M WTT028 WTP015 268711 CONTROL PANEL PARTS ...

Page 30: ...6 4 33112U WTT021 36549S WTP013 33390G 35889A 33052M 340511 OVEN CAVITY PARTS ...

Page 31: ...6 5 43501A 43500A 466001 WSZ084 466003 466001 44510A LATCH BOARD PARTS ...

Page 32: ...6 6 WSZ002 WTT028 WTT028 WSZ062 WSZ002 WTT037 50CZZH 56324A 55262A 54810C 55900A 56549F 56411A 56930V 568771 54974S 56912B WSZ002 34930W 50FZZA 56201A WSZ002 56901A 56851D 948503 INTERIOR PARTS ...

Page 33: ...6 7 56170D 63302A 63303A WTT021 WSZ002 65006B 948501 BASE PLATE PARTS ...

Page 34: ...8 1 SCHEMATIC DIAGRAM OF P C B ...

Page 35: ...8 2 PRINTED CIRCUIT BOARD ...

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