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LG MB-4022G, Service Manual

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LG MB-4022G Service Manual Download Page 24

5-14

(TROUBLE 3) Output power is low.

CONDITION

CHECK

RESULT

CAUSE

REMEDY

Output is low

Lower than 207V.

Normal

Less than 8.5

o

C.

Measure the
magnetron’s
output(See test
procedure).

Faulty magnetron.

Replace. 

Decrease in power
source voltage
with load.

Suggest customer
contact local
electric power
utility co. or
qualified
electrician.

Check the
power source
voltage
oscillating.

No continuity.

No continuity.

replace.

Malfunction of the
timer switch.

Faulty thermostat.

replace.

Check the
continuity of the
timer switch
contacts.

Check the
continuity of the
thermostat.

CONDITION

CHECK

RESULT

CAUSE

REMEDY

(TROUBLE 4) Grill.

CONDITION

CHECK

RESULT

CAUSE

REMEDY

1. Heater is not

operating.

Abnormal.

Normal.

Normal.

Heater.

Thermostat
(Grill)

Abnormal.

Malfunction the
thermostat.

Malfunction the
heater.

Replace.  

Wire connection.

No continuity.

Open or loosen.

Replace.  

Replace.  

Summary of Contents for MB-4022G

Page 1: ...MICROWAVE OVEN SERVICE MANUAL MODEL MB 4022G CAUTION BEFORE SERVICING THE UNIT READ THE SAFETY PRECAUTIONS IN THIS MANUAL website http biz lgservice com ...

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: ... 2M213 240GP 60 Min 455 W x 281 H x 313 D mm 312 W x 203 H x 293 D mm 12 0 kg approx 13 2 kg approx Microwave Power for Variable Cooking Power level Max 500W 350W Defrost 70W Grill Combi 1 2 3 Owner s manual Glass tray Roller Rest Grill rack 1 1 ITEM MODEL Power Requirement Power Output Microwave Frequency Magnetron Timer Outside Dimensions Cavity Dimensions Net Weight Shipping weight Control Comp...

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: ...L PANEL Safety Door Lock System Control Panel Window Door Screen Door Seal Oven Front Plate Grill Rack Turntable Roller Rest 1 2 1 POWER CONTROL KNOB Used in selected the desired power level for cooking 2 TIMER KNOB Used to set the cooking time ...

Page 8: ...the food on the rack in the oven and close the oven door 2 Set the function 3 Set the timer to the desired cooking time The turntable begins to rotate cooking starts and the lamp is turned on At the end of the cooking time you will hear a ring sound and the lamp is turned off COMBI COOKING 1 Open the oven door place the food on the rack in the oven and close the oven door 2 Set the 1 2 3 function ...

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

Page 10: ...gnetron filament through two noise preventing choke coils A high voltage of approximately 2100 volts AC is generated in the secondary of the high voltage transformer which is increased by the action of the diode and charging of the high voltage capacitor The negative DC voltage is then applied to the filament of the magnetron WHEN THE DOOR IS OPENED DURING COOKING Both primary switch and secondary...

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: ...ter 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 c...

Page 13: ... final water temperature and the ambient temperature is 5 K The microwave power output P in watts is calculated from the following formula 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 Stirring devices a...

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 gui...

Page 15: ... 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 is e...

Page 16: ...EN 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 button while making adjustment Make sure that the latch move...

Page 17: ... 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 op...

Page 18: ...NT TEST PROCEDURE 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 Between Filament terminal 2 Measu...

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 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...

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 Check for continuity of the H V Fuse with multi meter NOTE Make sure heater is fully cooled when tested Measure the resistance Multi meter scale Rx1 Normal Grill heater Approx 38 ohm at 20 30o C Normal more than 0 5 Mohm Normal Abnormal Measure the...

Page 21: ...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 C 2 3 B 2 M A 1 2 A B C A Turn on Approx 250Ω Turn Off B FAN MOTOR Wire leads removed TURNTABLE MOTOR Wire leads removed Normal Abnormal or several Ω Normal Appro...

Page 22: ...oading 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 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 powde...

Page 23: ...ned Disconnect one side of the wire lead connected from transformer to the high voltage capacitor and operate the unit Replace fuse 1 Oven does not operate No continuity No continuity Adjust or replace Malfunction of the primary switch Malfunction of the secondary switch Adjust or replace Check the continuity of the primary switch with door closed Check the continuity of the secondary switch with ...

Page 24: ...ician Check the power source voltage oscillating No continuity No continuity replace Malfunction of the timer switch Faulty thermostat replace Check the continuity of the timer switch contacts Check the continuity of the thermostat CONDITION CHECK RESULT CAUSE REMEDY TROUBLE 4 Grill CONDITION CHECK RESULT CAUSE REMEDY 1 Heater is not operating Abnormal Normal Normal Heater Thermostat Grill Abnorma...

Page 25: ...nitor resistor Abnormal Defective AC relay Replace Normal Check the AC relay Abnormal Open the secondary winding of the high voltage transformer of faulty insulation of filament winding Replace Check H V transformer Abnormal Shorted H V diode Replace Check H V diode Abnormal Faulty capacitor Replace Check H V capacitor Abnormal Faulty magnetron Replace Magnetron Abnormal Faulty H V Fuse Replace Ch...

Page 26: ...6 1 EXPLODED VIEW INTRODUCTION ...

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

Page 28: ...6 3 24781T 26549T WTT021 249401 23572A 368771 249402 CONTROL PANEL PARTS ...

Page 29: ...6 4 WTT010 WTT021 WTT021 33112U 33550H 35264A 33052M WTP013 WSZ184 35300S 33390G 36549S 56930G 948502 35889A 35026G WNZ015 OVEN CAVITY PARTS ...

Page 30: ...6 5 466001 43500A WSZ085 466003 466001 44510A LATCH BOARD PARTS ...

Page 31: ...6 6 56411A 568771 56930V 50FZZA 56201A 55900A WTT037 56549F WSZ002 WSZ002 WSZ062 WTT021 33808A 54974S WSZ002 WTT028 56851D 50CZZH 948501 54810C 56912B 55262A 56324A 34930W WSZ002 INTERIOR PARTS ...

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

Page 33: ...P NO 3828W5S3283 June 2003 Printed in Korea ...

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