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LG MH2044DB, Service Manual

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LG MH2044DB Service Manual Download Page 19

5-9

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

Chassis

Filament

HIGH VOLTAGE
CAPACITOR

Measure the resistance.
(Ohm-meter scale: Rx1000)
• Terminal to terminal.

Normal: Momentarily indicates

several ohms, and then
gradually returns to
infinite.

Normal: Infinite.

Normal: Continuity.
Abnormal: Infinite.

Normal: Infinite.
Abnormal: Continuity.

Measure the resistance.
(Ohm-meter scale: Rx1000)
• Terminal to case.

Measure the continuity (Forward).
(Ohm-meter scale: Rx10000)

Measure the continuity (Reverse).
(Ohm-meter scale: Rx10000)

HIGH VOLTAGE
DIODE

NOTE :
Some inexpensive meters
may indicate infinite
resistance in both direction.

COMPONENTS TEST 

PROCEDURE  RESULTS

Summary of Contents for MH2044DB

Page 1: ...MODEL MH2044DB MICROWAVEOVEN SERVICEMANUAL CAUTION BEFORESERVICINGTHEUNIT READTHESAFETYPRECAUTIONSINTHISMANUAL 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: ...4 1 OPERATING 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 ...

Page 4: ...oses DESCRIPTION 230 Volts AC 50 Hz Single phase 3 wire grounded 2450 MHz 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 turntable ITEM Model Power Requirement Power Output Microwave Frequency Magnetron Ti...

Page 5: ...ron 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 dur...

Page 6: ...possible from TV RADIO COMPUTER etc 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 ...

Page 7: ... 1 FEATURES CONTROL PANEL 4 1 OPERATING INSTRUCTIONS Roller Rest Safety Door Lock System Window Door Screen Door Seal Grill rack Turntable Control Panel Oven Front Plate 1 MICRO Used to select micro cooking 2 GRILL Used to select grill cooking 3 COMBI Used to select Combi cooking 4 AUTO COOK Used to cook the foods listed by one touch 8 START QUICK START To quickly set the cooking time directly 2 3...

Page 8: ...r return to the last item entered or to the clock 3 QUICK START 4 MICROWAVE COOKING 5 GRILL COOKING 6 COMBI COOKING 7 MULTI STAGE MICROWAVE COOKING 1ST STAGE 2ND STAGE This oven has a CHILD LOCK feature TO SET CHILD LOCK Touch the STOP pad Touch STOP CLEAR pad L appear on the display TO CANCEL CHILD LOCK Touch the STOP pad touch STOP CLEAR pad L disappears STOP CLEAR CLOCK CLOCK NUMBER START STOP ...

Page 9: ...MGT THERMAL GRILL SCHEMATIC DIAGRAM 4 3 7 5 3 1 8 BN ...

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: ...ervicing The power density of the microwave radiation leakage emitted by the microwave oven should not exceed 5 mW cm2 Always start measuring of an unknown field to assure safety for operating personnel from radiation leakage NECESSARY MEASURING INSTRUMENTS TESTER VOLTS DC AC Ohmmeter Microwave survey meter Holaday HI 1500 HI 1501 Narda 8100 8200 Inch scale 600 cc non conductive material beaker gl...

Page 12: ...e test probe must be removed no faster 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 befween 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 t...

Page 13: ...ure 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 bowl 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 measu...

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: ...st be below the limit of 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 turntable shaft VERY CAREFULLY 3 Lay the unit down on its back 4 Remove the turnt...

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

Page 17: ...er 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 open conditio...

Page 18: ...OVEN HIGH VOLTAGE TRANSFORMER Wire leads removed MAGNETRON Wire leads removed Approx 1 4 ohm Approx 90 ohm Less than 1 ohm Normal Infinite Normal Infinite Normal Less than 1 ohm Normal Infinite PRIMARY TERMINAL SECONDARY WINDING FILAMENT WINDING TERMINAL COMPONENTS TEST PROCEDURE RESULTS 1 Measure the resistance Ohm meter scale Rx1 Primary winding Secondary winding Filament winding 2 Measure the r...

Page 19: ...ormal Momentarily indicates several ohms and then gradually returns to infinite Normal Infinite Normal Continuity Abnormal Infinite Normal Infinite Abnormal Continuity Measure the resistance Ohm meter scale Rx1000 Terminal to case Measure the continuity Forward Ohm meter scale Rx10000 Measure the continuity Reverse Ohm meter scale Rx10000 HIGH VOLTAGE DIODE NOTE Some inexpensive meters may indicat...

Page 20: ...place the defective switch and the fuse at the same time Replace just the fuse if the switches operate normally Normal Abnormal Normal Abnormal H V FUSE HEATER ELEMENT Wire leads removed Measure the resistance Multi meter scale Rx1 Measure the resistance with 500V 100M ohm insulation resistance meter NOTE Make sure heater is fully cooled when tested Normal Grill heater Approx 38 ohm at 20 30 C GRI...

Page 21: ... P C B connector Cooking Start OFF Cooking Start OFF Normal Abnormal or several Ω Normal Approx 100 200 Abnormal or several Ω Measure the resistance Ohm meter scale R x 1000 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 NO...

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: ...isual conditions indicate a probable defective control circuit 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 exampl...

Page 24: ... Check continuity of magnetron thermostat No continuity 1 Fuse blows Continuity Malfunction of the monitor switch Replace defective switch 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 Normal Abnormal Defective magnetron Replace magnetron Defec...

Page 26: ...sformer 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 CONDITION CHECK RE...

Page 27: ...he heater Replace Heater Normal Abnormal Malfunction the thermostat Replace Thermostat and relay3 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 Operates properly on HIGH NOTE Make sure the wore leads corre...

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

Page 29: ...DOOR PARTS EV 13581A ...

Page 30: ...CONTROLLER PARTS EV 24781M ...

Page 31: ...33390B 33112U 44360A 33052M 35300A 36549S 35889A 33390G 35026G ...

Page 32: ...LATCH BOARD PARTS 466001 466003 466001 43500A 569128 EV ...

Page 33: ...54974A INTERIOR PARTS 50CZZH 56851D 55900A 56549F 568771 56930V 56411A 56324A 56930G 50FZZA 56201A EV 56930M 34810J 34810H 92502G ...

Page 34: ...BASE PLATE PARTS 56170D EV ...

Page 35: ...R SERVICE PARTS 7 1 REPLACEMENT PARTS LIST ...

Page 36: ......

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