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LG MB-4384B, Service Manual

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LG MB-4384B Service Manual Download Page 26

5-16

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

Defective high
voltage capacitor.

Replace high
voltage capacitor.

Check H.V.
capacitor.

Abnormal

normal

Defective high
voltage
transformer.

Replace high
voltage
transformer .

Check H.V.
transformer.

Abnormal

Defective high
voltage Diode.

Replace high
voltage Diode.

Check H.V.
diode.

normal

Abnormal

Defective
magnetron.

Replace
magnetron .

Check
Magnetron.

normal

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

(Display operates properly)

Summary of Contents for MB-4384B

Page 1: ...MICROWAVE OVEN SERVICE MANUAL MODEL MB 4384B CAUTION BEFORE SERVICING THE UNIT READ THE SAFETY PRECAUTIONS IN THIS MANUAL Website http biz lgservice com P NO 3828W5S3886 July 2004 Printed in Korea ...

Page 2: ...r 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 the interlock monitor door seal...

Page 3: ...TING SEQUENCE 4 2 SCHEMATIC DIAGRAM 4 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 CONTENTS ...

Page 4: ...D mm 14 5 kg approx 16 5 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 power LOW WARM approx 20 of Full power Owner s manual Glass tray Rotating ring Grill rack 1 1 ITEM MODEL Power Requirement Power Output Microwave Frequency Magnetron Timer Outside Dim...

Page 5: ...tron 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 from danger in ordinary use extreme care should be taken du...

Page 6: ...to prevent interference 8 Do not touch the front glass during 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...

Page 7: ...cooking grill and combi 2 CLOCK Used to set the time of day 3 SPECIAL COOK Used to select the special cook 4 QUICK DEFROST Used to select the quick defrost 5 AUTO COOK Used to cook the foods listed by one touch 6 AUTO DEFROST Used to select the auto weight defrost 7 AUTO ROAST Used to select the auto roast cook 8 STOP CLEAR Used to stop over and clear all entries except time of day 9 DIAL 10 START...

Page 8: ...TO SET CHILD LOCK Touch the Stop pad Touch STOP pad L appear in the display TO CANCEL CHILD LOCK Touch the Stop pad Touch STOP pad L disappears 4 QUICK START 5 MICROWAVE COOKING 6 GRILL COOKING 7 COMBI COOKING 8 AUTO WEIGHT DEFROST 9 AUTO COOK 10 SPECIAL COOk 11 QUICK DEFROST 12 AUTO REHEAT Stop Clock Clock Set the hour Set the minutes Clock Stop Power Start Quick Start Time Stop Combi Start Quick...

Page 9: ... RD GRILLTHERMOSTAT G Y FUSE BN BN GRILL HEATER T T M PRIMARY SWITCH YL F M YL O L BK BK WH YL RD WH MAGNETRON FA H V CAPACITOR H V FUSE ALTERNATIVE H V DIODE F H V CAPACITOR CIRCUIT PROTECTOR RD INPUT POWER RELAY1 CN1 1 3 7 5 GN RELAY2 8 RELAY3 RELAY2 PK RELAY3 NOISE FILTER POWER AND CONTROL CIRCUIT BOARD L V TRA NSFORMER N L ...

Page 10: ...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 voltag...

Page 11: ...ich is graduated to 600 cc and place the beaker on the center 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 radi...

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: ...perature is 5 K The microwave power output P in watts is calculated from the following formula 4187 X T 0 55 X T2 T0 X M T T2 Temperature after heating T0 Temperature after bown 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 vessel prior to ...

Page 14: ... 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 3 Remove the two screws holding the the suction gu...

Page 15: ... 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 Rotating Ring 3 Lay the unit down on its back 4 Remove the turntable motor cover The turntable base cover...

Page 16: ...LATION 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 les than 0 5 mm 1 64 inch Don t push the door release button whil...

Page 17: ...s 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 o...

Page 18: ...S TEST PROCEDURE RESULTS HIGH VOLTAGE 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 met...

Page 19: ...r scale 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...

Page 20: ...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 NOTE Make sure heater is fully cooled when tested Check for continuity of the H V Fuse with multi meter Normal Grill heater Approx 38 ohm at 20 30o C Normal more than 0 5 Mohm Normal Abnormal Normal Abnormal Measure the resistance Multi meter scale...

Page 21: ...resistance Ohm meter scale R x 1 Measure the resistance Ohm meter scale R x 1000 Normal Abnormal or several Ω Normal Approx 100 200 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 CONNECTOR NOT THE WIRES A B C ...

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: ...ot turn on when the timer knob is pushed with door closed 1 Incomplete segments Segment missing Partial segment missing Digit flickering NOTE Slight flickering is normal 2 Colon does not turn on or blink 3 A distinct change in the brightness of one or more numbers in display 4 One or more digits in the display are not lighting 5 Display indicates a number different from one touched for example key...

Page 24: ...nuity of magnetron thermostat No continuity 1 Fuse blows Continuity Malfunction of the monitor switch Replace primary and monitor switches Check continuity of monitor switch with door closed Check continuity of primary switch with door opened No continuity Disconnect one side of the wire lead connected from transformer to the high voltage capacitor and operate the unit No continuity Continuity Sho...

Page 25: ...Loose connection Connection then tightly Output is low Lower than 90 of rating voltage Normal Decrease in power source voltage with load Suggest customer contact local electric power utility co or qualified electrician Check the power source voltage Disconnect the wire leads from relay 2 and check on and off time with multitester Abnormal Abnormal Abnormal Defective magnetron Replace magnetron Def...

Page 26: ...ive high voltage capacitor Replace high voltage capacitor Check H V capacitor Abnormal normal Defective high voltage transformer Replace high voltage transformer Check H V transformer Abnormal Defective high voltage Diode Replace high voltage Diode Check H V diode normal Abnormal Defective magnetron Replace magnetron Check Magnetron normal TROUBLE 5 No microwave oscillation even though oven lamp a...

Page 27: ...y3 Grill Normal 1 Lower tempera ture the oven Abnormal Malfunction the heater Replace Heater Normal Abnormal Malfunction the thermostat Replace Thermostat and relay3 Grill No continuity Open or loosen Replace or connect tightly Wire connection TROUBLE 6 Oven does not cook properly when programmed for the set power level Operates properly on HIGH TROUBLE 7 Grill NOTE Make sure the wore leads correc...

Page 28: ...DOOR PARTS LATCH BOARD PARTS CONTROL PANEL PARTS INTERIOR PARTS BASE PLATE PARTS OVEN CAVITY PARTS 6 1 EXPLODED VIEW INTRODUCTION ...

Page 29: ...6 2 13552A 14890A 13213A 13720D 14026A 14970A WTT028 13581A 13536A 13650A DOOR PARTS ...

Page 30: ...6 3 24781S 23572A 23790D 250201 250205 249401 249402 250203 250204 250202 268711 WTP013 CONTROL PANEL PARTS ...

Page 31: ...6 4 WTT011 35052M 33550H 36549S 35300A 33390G 34370T 35889A 35026G 33112U WSZ002 44360A WSZ002 WTP013 WNH001 368771 348102 348101 35026C WTT010 OVEN CAVITY PARTS ...

Page 32: ...6 5 466001 466003 WSZ085 466001 43500A LATCH BOARD PARTS ...

Page 33: ...6 6 568771 56930G 56930V WSZ062 56411A 50FZZA 56549F 56201A WTT028 WSZ002 54974S WTT037 55900A 50CZZH WSZ002 WSZ002 56851C WTT028 54810C 56324A WSZ002 WTP004 56912B 55262A 948501 56201B INTERIOR PARTS ...

Page 34: ...6 7 56170D 63303A WSZ002 WTT021 63302A 65006B BASE PLATE PARTS ...

Page 35: ......

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