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LG MB-3832E, Service Manual

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LG MB-3832E Service Manual Download Page 26

5-16

(TROUBLE 5) Oven does not cook properly when programmed for the set power level 

(Operates properly on HIGH)

CONDITION

CHECK

RESULT

CAUSE

REMEDY

Output is full when

you set lower
power level.

Abnormal.

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

Defective P.C.B.
assembly.

Replace P.C.B.
assembly.  

Summary of Contents for MB-3832E

Page 1: ...MICROWAVE OVEN SERVICE MANUAL MODEL MB 3832E MB 3832ET CAUTION BEFORE SERVICING THE UNIT READ THE SAFETY PRECAUTIONS IN THIS MANUAL Website http biz lgservice com ...

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: ...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 12 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: ...CRIPTION MB 3832E MB 3832ET 230 Volts AC 50 Hz 1 200 Watts Single phase 3 wire grounded 800 Watts full microwave power IEC60705 2 450 MHz 2M214 240GP 10 sec 99 min 50 sec 455 W x 281 H x 345 D mm 312 W x 203 H x 293 D mm 12 5 kg 14 kg 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 a...

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: ...Window Door Screen Door Seal Safety Door Lock System Turntable Roller Rest Control Panel 1 TIMER WEIGHT SELECTOR CONTROL Used to set the cooking time 2 POWER SELECTOR CONTROL Used in selected the desired power level for cooking 3 CLOCK Used to set the time of day 2 1 3 ...

Page 8: ... direction To cancel the operation when the oven is cooking it is advisable to turn the timer weight selector to zero Even though the timer weight selector is not rotating during cooking the setting time is elapsed This is not a fault For the repetitive use of same cook time it is not necessary to set the cook time again Just press the start key then the oven operates for the previous setting time...

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

Page 10: ...ive 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 average output power of microwave oven as POWER LEVEL refer to page 1 1 WHEN THE DOOR IS OPENED DURING COOKING Both the primary switch and relay 2 are cut off primary winding voltage of the high vo...

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: ...o 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 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 possi...

Page 13: ...n the final water temperature and the ambient temperature is 5 K The microwave power output P in watts is calculated from the following formula 4187 x T T is measured while the microwave generator is operating at full power Magnetron filament heat up time is not included about 3 sec The water is stirred to equalize temperature throughout the vessel prior to measuring the final water temperature St...

Page 14: ...en 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 noise filter and high voltage capacitor...

Page 15: ... below the limit of 5 mW cm2 With a 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 J 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 ...

Page 16: ... 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 5 mm 1 64 inch Don t push the door release b...

Page 17: ...r 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 circuit in the doo...

Page 18: ...DURE COMPONENTS 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 Filament terminal 2 Measure the resistance Ohm...

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 Abnormal Continuity Normal Continuity Abnormal NOTE When testing the magnetron be sure to install the magnetron gasket in the correct position and be sure that the gask...

Page 20: ...ntinuity of the fuse with an multi meter Check for P C B connector NOTE If the fuse is blown check the primary the secondary and the monitor switches H V D and H V C before replacing the fuse If the fuse is blown by improper switch operation replace the defective switch and the fuse at the same time Replace just the fuse if the switches operate normally Normal Abnormal 0 C Approx 110 C Approx 110 ...

Page 21: ...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 CONNECTOR NOT THE WIRES A B C FAN MOTOR Wire leads removed TURNTABLE MOTOR Wire leads removed Normal Abnormal or several Ω Normal Approx 100 200 Ω Abnormal or several Ω A B A C 40 60Ω 300 500Ω ...

Page 22: ... does not work Inserting many plug into one plug outlet and using them at the same time causes overloading 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 occurring Inconsistent intensity of microwave by their characteristics 1 Wrap the thinner part with aluminum f...

Page 23: ...uity 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 TROUBLE 1 Oven lamp does not turn on when the timer knob is turned with door closed NOTE All these switches must be replaced at the same time Refer to page 5 6 5 7 2 Fuse does not ...

Page 24: ... switch with door closed Check fan motor Check oven lamp Abnormal Abnormal Normal Defective fan motor Defective fan motor Replace fan motor Replace fan motor Loose connection Connection then tightly CONDITION CHECK RESULT CAUSE REMEDY Output is low Lower than 90 of rating voltage Normal Normal Abnormal Abnormal Measure the output power Disconnect the wire leads from relay 2 and check on and off ti...

Page 25: ...normal normal Defective high voltage transformer Replace high voltage transformer Check H V transformer normal normal Abnormal Defective high voltage Diode Replace high voltage Diode Check H V diode Abnormal Defective high voltage capacitor Replace high voltage capacitor Check H V capacitor Abnormal Defective magnetron Replace magnetron Check Magnetron TROUBLE 4 No microwave oscillation even thoug...

Page 26: ...e set power level Operates properly on HIGH CONDITION CHECK RESULT CAUSE REMEDY Output is full when you set lower power level Abnormal Disconnect the wire leads from relay 2 and check continuity relay 2 Operate the unit Defective P C B assembly Replace P C B assembly ...

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

Page 28: ...6 2 13581A 14970A 14026A 13552A 13536A 13213A 14890A 13720D DOOR PARTS ...

Page 29: ...6 3 24781S WTP004 268711 23572A 250201 249401 249402 23790D CONTROL PANEL PARTS ...

Page 30: ...6 4 WTT020 WTT021 WTT021 33112U 33550H 35264A 33052M WTP013 WSZ184 35300S 33390G 36549S 56930G 948502 35889A 35026G WNZ015 OVEN CAVITY PARTS ...

Page 31: ...6 5 466001 43500A WSZ085 466003 466001 44510A LATCH BOARD PARTS ...

Page 32: ...6 6 56411A 568771 56930V 50FZZA 56201A 55900A WTT037 56549F WTT024 WSZ002 WSZ062 WTT021 33808A 54974S 50CZZH WTT028 54810C 56912B 55262A 948501 56324A 34930W WSZ002 WSZ002 56851C 56851H INTERIOR PARTS ...

Page 33: ...6 7 56170D 948503 63302A WSZ002 WTT021 65006B 63303A BASE PLATE PARTS ...

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

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

Page 36: ...P NO 3828W5S2645 May 2003 Printed in Korea ...

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