LG MH6848G Service Manual Download Page 20 | Manualshive

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5-10

COMPONENTS

TEST PROCEDURE

RESULTS

FUSE

HEATER ELEMENT
(Wire leads removed.)

OVEN THERMOSTAT

Normal:
*Grill heater

Approx. 50 ohm
(at 20 ~ 30˚C)

Normal: more than 0.5 Mohm

Measure the resistance.
(Multi-meter scale: Rx1)

Check for continuity of the fuse with an
multi-meter.

Measure the resistance with 500V-100M ohm
insulation resistance meter.

NOTE: Make sure heater is fully cooled when tested.

NOTE: If the fuse is blown, check the primary, the secondary, and the monitor
switches, H.V.D. and H.V.C. before replacing the fuse.
If the fuse 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.

Normal Abnormal

0°C~Approx. 145°C

Over 145°C

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 MH6848G

Page 1: ...OVEN SERVICE MANUAL MODEL MH6848G CAUTION BEFORE SERVICING THE UNIT READ THE SAFETY PRECAUTIONS IN THIS MANUAL Website http biz lgservice com 삼 흥 정 판 P NO MFL30190716 March 2010 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: ...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: ...er 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 Grill COMBI Owner s manual Glass turntable Roller rest Grill rack ITEM MODEL Power Requirement Power Output Microwave Frequency Magnetron Timer Outside Dimensions Cavity Dimensions Net Weight ...

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: ...Used to select the auto weight defrost 8 MORE LESS Used to change cooking time WEIGHT Used to select the weight of food 9 COOK TIME Used to cook food for a desired time 10 STOP CLEAR Used to stop oven and clear all entries except time of day 11 START QUICK START To quickly set the cooking time directly Oven Front Plate Door Seal Control Panel Safety Door Lock System Window Door Screen Turntable Gr...

Page 8: ...L appear on the display TO CANCEL CHILD LOCK Touch the Stop Clear pad Touch STOP CLEAR pad L disappears 10 MORE LESS 11 QUICK WEIGHT DEFROST Stop Clear Set clock Touch start Set the correct hour Set the correct minute Touch start Stop Clear Desired power level Start Start Desired cooking time Stop Clear Quick start Stop Clear Grill Start Desired cooking Time Stop Clear Desired combi category Start...

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: ...Y 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 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 couple...

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: ... 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 is moved horizontally along the oven surfacee RECORD KEEPING AN...

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 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 measuring the final water temperature Stirring devices an...

Page 14: ...ge 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 guide ASS Y to the o...

Page 15: ...tached 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 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 pinc...

Page 16: ...ount 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 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 indicat...

Page 18: ...SFORMER 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 meter scale Rx1000 Filament to chassis Approx...

Page 19: ...r scale 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 ...

Page 20: ...n resistance meter NOTE Make sure heater is fully cooled when tested NOTE If the fuse is blown check the primary the secondary and the monitor switches H V D and H V C before replacing the fuse If the fuse 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 Normal Abnormal 0 C Approx 145 C Over 145 ...

Page 21: ...veral Ω Check for P C B connector Measure the resistance Ohm meter scale R x 1 Cooking Start OFF Cooking Start OFF 1 3 5 Relay 2 Relay 1 Relay 3 A B 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...

Page 22: ...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 23: ...r when cooking is finished 12 Beep sound is not heard when correct key is touched 5 13 TROUBLE 1 The following visual conditions indicate a probable defective control circuit CONDITION CHECK RESULT CAUSE REMEDY Everything works as specified Continuity No continuity Still have trouble Defective key membrane assembly Defective PCB assembly Loose connection Defective PCB assembly Replace key membrane...

Page 24: ...Continuity No continuity Continuity Shorted contact at the primary switch Replace primary and monitor switches No continuity Normal Defective high voltage capacitor Replace high voltage capacitor Fuse blows again Defective high volt age transformer Replace high volt age transformer Malfunction of the monitor switch Replace primary and monitor switches Check continuity of monitor switch with door c...

Page 25: ...l Abnormal Normal Defective fan motor Defective oven lamp Replace fan motor Replace oven lamp Loose connection Connect them 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 assembly...

Page 26: ...y of relay2 Operate the unit Abnormal Normal Defective high voltage transformer Replace high voltage transformer Check H V transformer 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 Normal Abnormal Defective magnetron Replace magnetron Check magnetron LGE Internal U...

Page 27: ...tron be sure to install the magnetron gasket in the correct position and in good condition CONDITION CHECK RESULT CAUSE REMEDY 1 Heater is not operating Abnormal Normal Abnormal Normal Thermostat and relay3 Grill Malfunction the heater Replace Malfunction the thermostat Replace Heater Abnormal Normal Grill Control Switch Malfunction the grill control switch Replace No continuity Wire connection Op...

Page 28: ...MAY000 MFL552 OWNERS MANUAL 6 1 EXPLODED VIEW INTRODUCTION EV MODEL ...

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

Page 30: ... 6 3 23572A 24781M WTP018 268711 24510L 250201 24970A 23506A 23790D CONTROL PANEL PARTS EV ...

Page 31: ... 6 4 33052M 36549S 35300A 33390G 35026G 44360A WTP013 WNH001 34810H 34810H 368771 WTT010 Button Head Torx style 2 33808A WSZ185 33112U 35889A OVEN CAVITY PARTS EV ...

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

Page 33: ...568771 56411A 50FZZA 56201A 56549F WTT037 WSZ062 WTT028 WSZ002 55900A 34930W 56851D 50CZZH 54810C WSZ002 56324A WSZ002 56912B 948501 55262A WTT028 WSZ002 54974S 56930V 56930G 56901A WSZ002 INTERIOR PARTS EV ...

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

Page 35: ......

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