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LG MJ3294BDB Service Manual Download Page 25

BASIC CHECK SUMMARY

5-13

Symptom : No Power 

-. Check :  

Symptom : no key 

-. Check :  

Symptom : no heat 

-. Check:  

1. Check connector electric wiring 
2. Door connector with CN1 

3. between the power code and  connector 
4. between the ends of, thermostat 

    ( OVEN MGT) 

1.  Secondary interlock switch 
     Door Connector with CN2 

2.  keypad connector Electric     
Wiring Display PCB with CN7 

1. MGT relay(RY2), Convection 

    relay(RY5) and Triac 
2. Primary switch 

3. MGT , HVT, Heater and  
    Thermistor  

LGE Internal Use Only

Copyright © 2009 LG Electronics. Inc. All right reserved. 
Only for training and service purposes

Summary of Contents for MJ3294BDB

Page 1: ...EN SERVICE MANUAL MODEL MJ3294BDB MJ3294BDW CAUTION BEFORE SERVICING THE UNIT READ THE SAFETY PRECAUTIONS IN THIS MANUAL P No MFL34869163 June 2015 Printed in Korea Website http biz lgservice com Internal Use Only ...

Page 2: ... 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 transmission systems shall ...

Page 3: ...RCUIT DESCRIPTION 4 6 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 BASIC CHECK SUMMARY 5 13 TROUBLE SHOOTING 5 14 EXPLODED VIEW 6 1 CONTENTS LGE Internal Use Only Copyright 2009 LG Electronics Inc All right reserved Only for t...

Page 4: ...r level max 900W Full power throughout the cooking time MED HIGH 720W approx 80 of Full power MEDIUM 540W approx 60 of Full power DEFROST 360W approx 40 of Full power LOW WARM 180W approx 20 of Full power CONVECTION max 230 C GRILL COMBINATION Owner s manual Glass Tray Rotating ring High rack Low rack Crispy Tray ITEM Power Requirement Power Output Microwave Frequency Magnetron Timer Outside Dimen...

Page 5: ...te 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 danger in ordinary use extreme care should be taken during repair THE OVEN IS TO BE SERVICED ONLY BY PROPERLY Q...

Page 6: ...ring or after cooking of the Grill and Combination mode This glass is very hot during heater operating 9 Do not operate the oven at microwave and combination mode with Grill rack placed in the cavity when the oven is empty 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 WAR...

Page 7: ...king times temperature and power level While cooking with auto and manual function you can increase or decrease the cooking time at any point by turning the dial except defrost mode 9 STOP CLEAR Stop over and clear all entries except time of day 10 START QUICK START In order to start cooking which is selected press button one time The quick start feature allows you to set 30 seconds intervals of H...

Page 8: ...MODE START QUICKSTART START QUICKSTART COOK MODE COOK MODE START QUICKSTART START QUICKSTART COOK MODE COOK MODE COOK MODE START QUICKSTART STOP CLEAR START QUICKSTART START QUICKSTART COOK MODE COOK MODE COOK MODE START QUICKSTART COOK MODE START QUICKSTART STOP CLEAR STOP CLEAR Touch and Hold STOP CLEAR STOP CLEAR Touch and Hold STOP CLEAR Desired cook START QUICKSTART COOK MODE STOP CLEAR COOK ...

Page 9: ...4 3 COMPOSITION OF CONTROL P N EBR73081807 Main PCB EAX64105602 LGE Internal Use Only Copyright 2009 LG Electronics Inc All right reserved Only for training and service purposes ...

Page 10: ...4 4 COMPOSITION OF CONTROL P N EBR79290901 Key PCB EAX66088301 LGE Internal Use Only Copyright 2009 LG Electronics Inc All right reserved Only for training and service purposes ...

Page 11: ...4 5 SCHEMATIC DIAGRAM LGE Internal Use Only Copyright 2009 LG Electronics Inc All right reserved Only for training and service purposes ...

Page 12: ...IMUM 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 complete cycle of relay 2 is 22 seconds WHEN THE DOOR IS OPENED DURING COOKING Both the primary switch and relay 2 are cut off primary winding voltage of the high voltage transformer ON OFF of relay 2 is coupled electrically wit...

Page 13: ...nter of the turntable Set the energy leakage monitor to 2 450 MHz and use it following the manufacturer s recommended test procedure to assure correct result When measuring the leakage always use the 2 inch 5cm spacer supplied with the probe Operate the oven at its maximum output Measure the microwave radiation using and electromagnetic radiation monitor by holding the probe perpendicular to the s...

Page 14: ... 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 is moved horizontally along the oven surface RECORD KEEPING AND...

Page 15: ... Temperature of bowl before heating M Weight of bowl 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 bowl prior to measuring the final water temperature Stirring devices and measuring instruments are selected in order to minimize addition or removal of heat W...

Page 16: ...t the leadwire from lamp and MGT thermostat 2 Remove the mounting screw to the magnetron G MAGNETRON REMOVAL 1 Disconnect the leadwire from the high voltage transformer and high voltage capacitor 2 Carefully remove the mounting screws holding the magnetron and the waveguide 3 Remove the magnetron ASS Y until the tube is clear from the waveguide NOTE 1 When removing the magnetron make sure its dome...

Page 17: ... 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 with a wire cutting 5 Disconnect the leadwire from the turntable motor terminals 6 Remove the screw securing the turntable motor to the oven cavity ASS Y...

Page 18: ...SS Y to the control panel 3 Disconnect the flat cable from the PCB SUB ASS Y and take off the PCB SUB ASS Y M INTERLOCK SYSTEM 1 INTERLOCK MECHANISM The door lock mechanism is a device which has been specially designed to eliminate 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 SECONDAR...

Page 19: ...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 open condition When the door is closed meter should indicat...

Page 20: ...R 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 Approx 1 9 o...

Page 21: ...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 22: ... switch operation replace the defective switch and the fuse at the same time Replace just the fuse if the switches operate normally NOTE Make sure heater is fully cooled when tested Measure the resistance Multi meter scale Rx1 Normal Grill heater Approx 42 ohm at 20 30o C Normal more than 0 5 Mohm Normal Abnormal Measure the resistance with 500V 100M ohm insulation resistance meter 0 C Approx 145 ...

Page 23: ...r P C B connector Normal Approx 200 400 ohm Abnormal Infinite or several ohm Normal Approx 10 20 kohm Abnormal Infinite or several ohm 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 CONNECTOR NOT THE WIRES A B Cooking Start OFF Relay...

Page 24: ...KAGE TEST MUST ALWAYS BE PERFORMED WHEN THE UNIT IS SERVICED FOR ANY REASON MAKE SURE THE WIRE LEADS ARE CORRECT POSITION WHEN REMOVING THE WIRE LEAD FROM THE PARTS BE SURE TO GRASP THE CONNECTOR NOT THE WIRES Relay 2 Relay 3 Relay 5 Cooking Start OFF CN2 1 3 4 5 9 6 8 Relay 6 Relay 4 COM YL 230V BL Cooking Start OFF Normal COM 230V Approx 150 Ω Abnormal Infinite or several ohm LGE Internal Use On...

Page 25: ...e and connector 4 between the ends of thermostat OVEN MGT 1 Secondary interlock switch Door Connector with CN2 2 keypad connector Electric Wiring Display PCB with CN7 1 MGT relay RY2 Convection relay RY5 and Triac 2 Primary switch 3 MGT HVT Heater and Thermistor LGE Internal Use Only Copyright 2009 LG Electronics Inc All right reserved Only for training and service purposes ...

Page 26: ...ONDITION Microwave oven 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 thinn...

Page 27: ...t No Power 1 Check connector electric wiring 2 Between the power code and connector 3 Between the ends of thermostat OVEN MGT LGE Internal Use Only Copyright 2009 LG Electronics Inc All right reserved Only for training and service purposes TROUBLE SHOOTING ...

Page 28: ...en Magnetron Heater No No 4 Replace the Thermostats 2 Replace the PCB EBR73081807 CN1 Is there any beep sound in Continuity test between the Power code and connector Code L to Pin3 Code N to Pin1 No No 3 Replace the PCB EBR73081807 L N Oven Thermostat Magnetron Thermostat Convection Heater Thermostat Yes Yes Yes Yes LGE Internal Use Only Copyright 2009 LG Electronics Inc All right reserved Only fo...

Page 29: ...in Continuity test between the Ends of noise filter No No 6 Reconnect or Repair the Connector Replace the Main PCB EBR73081807 Live Terminal of Noise filter Neutral Terminal of Noise filter Yes Yes LGE Internal Use Only Copyright 2009 LG Electronics Inc All right reserved Only for training and service purposes TROUBLE SHOOTING ...

Page 30: ...ndary interlock switch Door PCB with CN2 2 Check the Connection between Key PCB and Main PCB CN CN Door Closed Door Opened Resistance Short LGE Internal Use Only Copyright 2009 LG Electronics Inc All right reserved Only for training and service purposes TROUBLE SHOOTING ...

Page 31: ...any beep sound in Continuity test between the Ends of latch board Secondary Switch Door should be closed Yes No No 4 Reconnect or repair the connector Is the connector connected to MAIN PCB assembly disconnected or disassembled CN7 of Main PCB to CON1 of Key PCB Replace the Main PCB EBR73081807 Replace the Key PCB if Changing the Main PCB Doesn t resolve the problem 5 LGE Internal Use Only Copyrig...

Page 32: ...int No Heat No Cook 1 Check the MGT relay RY2 Convection relay RY5 and Triac 2 Check the primary switch 3 Check the MGT HVT Heater and Thermistor LGE Internal Use Only Copyright 2009 LG Electronics Inc All right reserved Only for training and service purposes TROUBLE SHOOTING ...

Page 33: ...isconnected or Disassembled No 2 Reconnect or Repair the connector Power Off Is there resistance of high voltage Transformer out of rage No No 3 Replace the High Voltage Transformer Test Point 1 Primary winding High Low 1 9 Ohm 3 Filament winding 1 Ohm 2 Secondary 180 Ohm Yes Yes LGE Internal Use Only Copyright 2009 LG Electronics Inc All right reserved Only for training and service purposes TROUB...

Page 34: ... connector connected To the high voltage diode Assembly disconnected or Disassembled Yes 6 Reconnect or repair the connector 7 Is the resistance of the high Voltage diode out of rage refer to 10 Replace the High voltage Diode Reconnect or Repair the connector Replace the High voltage Capacitor No No Yes Reconnect of repair the connector No LGE Internal Use Only Copyright 2009 LG Electronics Inc Al...

Page 35: ...le Motor No Yes Is there any beep sound in Continuity test between the Ends of latch board Primary switch Door should be closed No 4 Adjust the Primary latch board Replace the Main PCB EBR73081807 Yes Yes Replace Turntable Motor Reconnect or Repair the connector Test Point 10 20kohm LGE Internal Use Only Copyright 2009 LG Electronics Inc All right reserved Only for training and service purposes TR...

Page 36: ...times Does product operate Yes No No Alternate with Explanation Refer to the Note No 3 When door is closed does The oven lamp turn on No No Yes Replace the Turntable Motor 4 When the door is opened is The voltage of door sensing Part under 0V Pin 1 to Pin 3 of CN2 No Yes Replace the PCB EBR73081807 Turn on automatically Power ON CN2 LGE Internal Use Only Copyright 2009 LG Electronics Inc All right...

Page 37: ...DOOR PARTS CONTROL PANEL PARTS LATCH BOARD PARTS BASE PLATE PARTS INTERIOR PARTS OVEN CAVITY PARTS 6 1 EXPLODED VIEW INTRODUCTION EV Customer Model Product Code SVC Model MODEL ...

Page 38: ... 6 2 14810C W319 W319 13581A 13651A 13551C W316 W316 14810L 14510L 13213A 13552A 14510L 14810R DOOR PARTS EV ...

Page 39: ... 6 3 24781S 23572A 26871M 23806C 26871R 23550D CONTROL PANEL PARTS EV ...

Page 40: ... 6 4 35026C 33112U 35026G 33390A 34370T 35889A 33390G 36549S 348103 348103 55238U W101 W101 55238L W178 348102 330522 353001 353002 348101 348101 330521 44360A OVEN CAVITY PARTS EV ...

Page 41: ... 6 5 W102 W102 445102 44970A 466001 43500A 466003 466001 43501A 44970A 445101 44980A LATCH BOARD PARTS EV ...

Page 42: ... W140 W103 W124 55262A 56324A 34930W W101 W101 55900A 50CZZH 54810C 56851D 54974S 56549F 50FZZA 56201A 33809A 36549C 54810S 55900N W177 535041 535042 56930V 55900C 55300A 56322A 56930G 54810V W101 W125 W141 W102 W124 54350S 56930M INTERIOR PARTS EV ...

Page 43: ... 6 7 647781 64970A 64970A 648112 648111 W101 56170D 63302A 63303A BASE PLATE PARTS EV ...

Page 44: ......

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