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LG MH-2381NBR Service Manual Download Page 19

5-9

COMPONENTS

TEST PROCEDURE

RESULTS

HIGH VOLTAGE
CAPACITOR

HIGH VOLTAGE
DIODE

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

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

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)

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 gasket is in good condition.

Antenna

Gasket

Chassis

Filament

LGE Internal Use Only

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

Summary of Contents for MH-2381NBR

Page 1: ...N SERVICE MANUAL MODEL MH 2381NBR CAUTION BEFORE SERVICING THE UNIT READ THE SAFETY PRECAUTIONS IN THIS MANUAL Website http biz lgservice com P NO MFL32514623 February 2009 Printed in Korea 삼 흥 정 판 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: ...ON 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 LGE Internal Use Only Copyright 2007 LG Electronics Inc All right reserved Only for training and s...

Page 4: ...wer 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 High rack Low rack Crispy tray Scrubber 1 1 ITEM MODEL Power Requirement Power Output Microwave Frequency Magnetron Timer Outside Dimensions Cavity Dimensions Net Weight Shipping...

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: ...d to crispy cook 4 AUTO DEFROST To select auto defrost 5 AUTO COOK Used to select the auto cook 6 MICRO Used to select the power level for microwave cooking 7 GRILL Used to select the grill cooking 8 COMBI Used to select the combination cooking 9 KEEP WARM Used to keep warm 10 DIAL To select convection temperature change cooking time and weight 11 QUICK START To quickly set the cooking time direct...

Page 8: ...eturn to the last item entered or to the clock 3 CHILD LOCK This oven has a CHILD LOCK feature TO SET CHILD LOCK Touch the Clear pad Touch Clear pad L appear in the display TO CANCEL CHILD LOCK Touch the Clear pad Touch Clear pad L disappears 4 QUICK START 5 MICROWAVE COOKING 6 GRILL COOKING 7 COMBI COOKING 8 AUTO WEIGHT DEFROST 9 AUTO COOK 10 CRISPY COOKING 11 KEEP WARM Clear Clock Clock Set the ...

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: ... 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 voltage transformer ON OFF of relay 2 is coupled electrically wi...

Page 11: ...enter of the turntable Set the energy leakage monitor to 2450 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: ...alse 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 RECORD KEEPING AND NOTIFICATION AFTER M...

Page 13: ...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 measuring the final water temperature Stirring devices an...

Page 14: ...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 guide ASS Y to the oven cavity and remove the high voltage diod...

Page 15: ...rowave 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 easily removed by pinching the six parts with a wire cutting 5 Disconnect the leadwire from the turntabl...

Page 16: ...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 while making adjustment Make sure that the latch moves smoothly af...

Page 17: ... 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 indica...

Page 18: ...ads 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 2 5 Ω Approx 1...

Page 19: ...rward 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 gasket is in good condition Antenna Gasket Chassis Filam...

Page 20: ...ive 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 30oC Normal more than 0 5 Mohm Normal Abnormal Normal Abnormal Measure the resistance Multi meter scale Rx1 Measure the resistance with 500V 100M ohm insulation...

Page 21: ...hm 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 Cooking Start OFF Cooking Start OFF 1 3 5 Relay 2 Relay 1...

Page 22: ...nd 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 foil 2 Use plastic wrap or lid 3 Stir once or twice while ...

Page 23: ... 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 in 5 and 3 appears in the display 6 Specific numbers for...

Page 24: ...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 Shorted contact at the primary switch Replace primary and mo...

Page 25: ...wer 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 Defective P C B assembly Replace P C B assembly Measure the ...

Page 26: ... 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 LGE Internal U...

Page 27: ...tion 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 are in the correct position When removing the wire leads from parts ...

Page 28: ... 6 1 EXPLODED VIEW INTRODUCTION EV MODEL ...

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

Page 30: ... 6 3 WTP004 268711 24781S 23572A 23806C 25020M 25020S 243501 249401 WTP013 268712 CONTROL PANEL PARTS EV ...

Page 31: ... 6 4 95001B 33390M WTT011 33052M 36549S 35300A 33390G 34370T 35889A 33112U WTT021 44360A WTP013 WNH001 368771 35026C 35026G 34810H 34810H OVEN CAVITY PARTS EV ...

Page 32: ... 6 5 466003 466001 43501A 43500A 466001 WSZ085 44510A LATCH BOARD PARTS EV ...

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

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

Page 35: ......

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