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MICROWAVE OVEN

SERVICE MANUAL

MODEL: MS3447GR

MS3447GRS

CAUTION

BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.

Website http://biz.lgservice.com

P/NO : MFL31039007

July, 2007

Printed in Korea

삼

흥

정

판

Internal Use Only

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Summary of Contents for MS3447GR

Page 1: ...SERVICE MANUAL MODEL MS3447GR MS3447GRS CAUTION BEFORE SERVICING THE UNIT READ THE SAFETY PRECAUTIONS IN THIS MANUAL Website http biz lgservice com P NO MFL31039007 July 2007 Printed in Korea 삼 흥 정 판 Internal Use Only ...

Page 2: ...ening 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 and microwave generation and transmis...

Page 3: ...ESCRIPTION 4 5 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 LGE Internal Use Only Copyright 2007 LG Electronics Inc All right reserved Only for training and se...

Page 4: ...ower 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 cooking guide Glass turntable Roller rest ITEM MODEL Power Requiremen Power Output Microwave Frequency Magnetron Timer O...

Page 5: ...t 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 Unlike other appliances the microwave oven is high voltage and high current equipment Though it is free from danger in ordinary use extreme care should be taken duri...

Page 6: ... 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 wires in the mains lead of this appliance may not correspond ...

Page 7: ...onds to the cooking time LESS Pressing LESS will subtract 10 seconds of cooking time 7 QUICK DEFROST You can thaw specific foods and weight very quickly 8 NUMBER These used to set for time of day cooking time power level or defrost weight 9 CLOCK It is used to set the time of day 10 POWER You can select power level for cooking 11 STOP CLEAR It used to stop oven and clear all entries except time of...

Page 8: ...ure TO SET CHILD LOCK Touch STOP CLEAR pad Touch and hold STOP CLEAR pad LOCKED appears on the display TO CANCEL CHILD LOCK Touch and hold STOP CLEAR pad LOCKED disappears 7 MORE LESS The cook time is adjustable by MORE pad or LESS pad 8 AUTO REHEAT NOTE Then the oven will start automatically 9 Q UICK DEFROST 10 AUTO COOK NOTE Then the oven will start automatically STOP CLEAR POPCORN NUMBER OF TAB...

Page 9: ...SCHEMATIC DIAGRAM 4 3 LGE Internal Use Only Copyright 2007 LG Electronics Inc All right reserved Only for training and service purposes ...

Page 10: ...ansformer which is increased by the action of the high voltage diode and charging of the high voltage capacitor The negative 4000 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 One c...

Page 11: ...it until the oven has been brought into compliance If the oven operates with the door open the service personnel should Tell the user not to operate the oven Contact the manufacturer The service personnel should check all surface and vent openings for microwave leakage Check for microwave leakage after every servicing The power density of the microwave radiation leakage emitted by the microwave ov...

Page 12: ...e shaded area otherwise a false reading may result The test probe must be held by 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 Hold vertically when testing the top and bottom and horizont...

Page 13: ...ximately 190mm 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 thd lowest position and the microwave power switched on The time...

Page 14: ...o check that the primary switch monitor switch and secondary 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 4 mW cm2 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 betw...

Page 15: ... the mounting screws properly making sure there is no gap between the waveguide and the magnetron H REMOVING THE TURNTABLE MOTOR 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 Disconnect the leadwire from the turntable motor terminals 5 Remove th...

Page 16: ...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 ADJUSTMENT OF THE LATCH BOARD TO THE OVEN ASSEMBLY Mount the latch board to the oven assembly Adjust the latch board...

Page 17: ...condary 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 open condition When the door is closed meter should indicate ...

Page 18: ...TRANSFORMER Wire leads removed MAGNETRON Wire leads removed 1 Measure the resistance Ohm meter scale Rx1 and Rx100 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 meter scale Rx1000 Filament to chassis Ap...

Page 19: ...r scale Rx10000 Measure the continuity Reverse Ohm meter scale Rx10000 Normal Momentarily indicates several ohms and then gradually returns to infinite Normal Infinite Normal Continuity Abnormal Infinite Normal Infinite Abnormal Continuity NOTE When testing the magnetron be sure to install the magnetron gasket in the correct position and be sure that the gasket is in good condition Antenna Gasket ...

Page 20: ...RECT POSITION WHEN REMOVING THE WIRE LEADS FROM THE PARTS BE SURE TO GRASP THE CONNECTOR NOT THE WIRES 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 18 sec 16 sec 14 sec 12 sec 10 sec 8 sec 6 sec 4 sec 2 sec 0 sec POWER LEVEL Relay 2 A B Measure the resistance Ohm meter scale R x 1 Check for continuity of relay 2 with an ohm meter Remove wire leads from re...

Page 21: ... input voltage Food temperature is too low Using metallic ware and allowing it to touch the oven wall Sparks occur Inconsistent intensity of microwave by their characteristics 1 Use plastic wrap or lid 2 Stir once or twice while cooking soup cocoa or milk etc Uneven cooking Ceramic ware trimmed in gold or silver powder is used Avoid using other electrical appliances when you use the microwave oven...

Page 22: ...play time of day does not reappear when cooking is finished TROUBLE 1 The following visual conditions indicate a probable defective control circuit CONDITION CHECK RESULT CAUSE REMEDY Everything works as specified Continuity No continuity Still have trouble Defective key membrane assembly Defective PCB assembly Loose connection Defective PCB assembly Replace key membrane assembly Replace PCB assem...

Page 23: ... the wire lead connected from transformer to the high voltage capacitor and operate the unit Replace fuse Continuity Malfunction of secondary switch Replace fuse primary monitor secondary switches and RELAY RY2 of P C B Assembly No continuity Check continuity of secondary switch with door opened TROUBLE 2 Oven does not operate at all Display window does not display any figures and no input is acce...

Page 24: ...al Abnormal Normal Defective fan motor Defective oven lamp Replace fan motor Replace oven lamp Loose connection Connect them 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 time with multitester Defective PCB assembly Replace PCB assembly De...

Page 25: ... tage capacitor Abnormal Defective magnetron Replace magnetron Check magnetron TROUBLE 5 No microwave oscillation even though oven lamp and fan motor run Display operates properly 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 NOTE Make sure the wire leads ...

Page 26: ...EXPLODED VIEW 6 1 INTRODUCTION INTERIOR PARTS OVEN CAVITY PARTS DOOR PARTS CONTROL PANEL PARTS BASE PLATE PARTS LATCH BOARD PARTS EV MODEL MS3447GR MS3447GRS ...

Page 27: ...DOOR PARTS 6 2 13552A 13213A 13581A 14970A 14026A 13536A 15006A 13720D 14890A EV ...

Page 28: ...CONTROL PANEL PARTS 6 3 23572A 23790D 23506A 24781M WTP018 268711 24510L 250201 24970A EV ...

Page 29: ...OVEN CAVITY PARTS 6 4 33390G WTT010 WTT021 33112U 35889A 36549S WTP013 33052A EV ...

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

Page 31: ...062 WSZ002 WEB001 WSZ002 WSZ002 WTT028 WTT028 56411A 56930V 50FZZA 56201A 56549F 54974S WTT037 55900A 54810C WTT028 50CZZH 34930W 56324A 55262A 56912B 56201B 948502 948501 54974T 56501A WTP004 WTT021 WSZ002 56851D 35012A 56901A EV ...

Page 32: ...BASE PLATE PARTS 6 7 56170D WSZ002 WTT021 63302A 65006B 63303A 948502 EV ...

Page 33: ......

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