LG MJ3284UAB Service Manual Download Page 27 | Manualshive

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5-17

CONDITION

CHECK

RESULT

CAUSE

REMEDY

No microwave
oscillation.

No continuity.

Continuity.

Defective P.C.B
assembly

Replace P.C.B
assembly

Disconnect the
wire leads from
relay 2 and
check continuity
of relay2.
(Operate the
unit)

Abnormal

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

(Display operates properly)

LGE Internal Use Only

Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes

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Summary of Contents for MJ3284UAB

Page 1: ...E OVEN SERVICE MANUAL MODEL MJ3284UAB CAUTION BEFORE SERVICING THE UNIT READ THE SAFETY PRECAUTIONS IN THIS MANUAL Website http biz lgservice com P NO MFL32190946 August 2015 Printed in Korea 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: ...VICE 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 13 TROUBLE SHOOTING Display shows error mode 5 19 EXPLODED VIEW 6 1 CONTENTS LGE Internal Use Only Copyright 2007 LG Electronics Inc All right reserved Only for trai...

Page 4: ... 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 250 C GRILL COMBINATION Owner s manual Cook book Glass turntable Rotating ring High rack Low rack 1 1 ITEM Power Consumption 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: ...or microwave cooking 8 GRILL Used to select the grill cooking 9 CONV Used to select the convection cooking 10 COMBI Used to select the combination cooking 11 DIAL To select convection temperature change cooking time and weight 12 START Q START To quickly set the cooking time directly 13 STOP CLEAR Used to stop oven and clear all entries except time of day Turntable Rotating Ring Safety Door Lock S...

Page 8: ... 9 AUTO DEFROST 10 QUICK START 11 LEAN ROAST 12 AUTO COOK 13 CONVECTION Start Stop Clear Defrost Bake DIAL Start Stop Clear Lean Roast DIAL Start DIAL Stop Clear Quick Start Stop Clear Select Clock Desired power level DIAL Desired cooking time Start Stop Clear Grill DIAL Start Stop Clear Ez clean Start Stop Clear Crispy Reheat DIAL Start Stop Clear Auto Cook Start DIAL Stop Clear Convection Stop C...

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: ...VEL 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 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 el...

Page 11: ...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 12: ... 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 this may possibly cause probe damage...

Page 13: ...f bowl is measured while the microwave generator is operating at full power Magnetron filament heat up time is not included The water is stirred to equalize temperature throughout the vessel prior to measuring the final water temperature Stirring devices and measuring instruments are selected in order to minimize addition or removal of heat WATER LOAD TURNTABLE MEASUREMENT OF MICROWAVE POWER OUTPU...

Page 14: ...re from lamp 2 Remove the mounting screw to the cavity 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 does not hit any adjacent parts o...

Page 15: ...transformer and capacitor 3 Remove the screw holding the high voltage transformer to the baseplate K THE TURNTABLE MOTOR REMOVAL 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 eight parts with a wire cutting 5 Disconnect the le...

Page 16: ...ISM 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 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 Ad...

Page 17: ... 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 an open circuit When the monitor swi...

Page 18: ...TRON 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 2 0 ohm Approx 150 ohm Less tha...

Page 19: ...le 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 Chass...

Page 20: ...h 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 Convection heater Approx 63 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 60 C ...

Page 21: ...OTOR Wire leads removed Measure the resistance Ohm meter scale R x 1 Measure the resistance Ohm meter scale R x 1000 Check for P C B connector Normal Approx 300 500 ohm Abnormal Infinite or several ohm Normal Approx 10 20 kohm Abnormal Infinite or several ohm B Cooking Start OFF Relay 2 Relay 3 Relay 5 1 2 3 4 5 6 7 8 9 Cooking Start OFF LGE Internal Use Only Copyright 2007 LG Electronics Inc All ...

Page 22: ...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 Normal COM 230V Approx 160 Ω Abnormal Infinite or several ohm LGE Internal Use Only Copyright 2007 LG Electronics Inc All right reserved Only for training and service purposes ...

Page 23: ...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 24: ...ator light does not turn on after setting 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 14 TROUBLE 1 The following visual conditions indicate a probable defective control circuit CONDITION CHECK RESULT CAUSE REMEDY Everything works as specified Still have trouble Defective key membrane assembly Defective PCB...

Page 25: ...th door opened Disconnect one side of the wire lead connected from transformer to the high voltage capacitor and operate the unit Replace fuse TROUBLE 2 Oven does not operate at all Display window does not display any figures and no input is accepted NOTE All these switches must be replaced at the same time Refer to page 5 6 5 7 2 Fuse does not blow No continuity No continuity Replace power supply...

Page 26: ... Abnormal Normal Defective fan motor Defective oven lamp Replace fan motor Replace oven lamp 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 time with multitester Defective P C B assembly Replace P C B assemb...

Page 27: ...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 5 No microwave oscillation even though oven lamp and fan motor run Display operates properly LGE Internal U...

Page 28: ...ok 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 NOTE Make sure the wire leads are in the correct position When removing the wire leads from parts ...

Page 29: ...ace the P C B assembly CONDITION CHECK RESULT CAUSE REMEDY Display shows F02 No continuity Continuity Normal Abnormal Check the thermistor Defective thermistor Thermistor opened Replace the thermistor Loose connection Connect them tightly Check the connnection between Thermistor and P C B assembly Normal Abnormal Check the heater Defective heater Heater opened Replace the heater Defective P C B As...

Page 30: ...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 31: ... 6 2 DOOR PARTS EV 13552A 13581A 14026A 14970A 13213A 13551C 13650A ...

Page 32: ... 6 3 CONTROL PANEL PARTS EV 24781A 26871T 26871M 24781S 250202 250201 249401 24941A ...

Page 33: ... 6 4 35026C 33112U 35026G 34370T 35889A 33390G 36549S 348103 348103 W178 348102 55238L 330522 353001 353002 348101 348101 330521 44360A 55238U W101 W101 OVEN CAVITY PARTS EV ...

Page 34: ... 6 5 W102 43501A 466001 43500A 466003 44510A 466001 LATCH BOARD PARTS EV ...

Page 35: ... W140 W103 W129 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 36: ... 6 7 647781 W101 56170D 63302A 63303A BASE PLATE PARTS EV ...

Page 37: ......

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