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LG MS-1942G Service Manual Download Page 25

5-15

(TROUBLE 3) Display shows all figures set, but oven does not start cooking while          

desired program times are set and START pad is touched.

(TROUBLE 4) Oven seems to be operation but little heat  is produced in oven load.

CONDITION

CHECK

RESULT

CAUSE

REMEDY

1.Setting time does

not count down
when touching
START pad.

2. Fan motor or

oven lamp
do not turn
on.

No continuity.

continuity.

No continuity.

Continuity.

Check the con-
nection between
connector and
P.C.B assembly.

Defective
secondary switch.

Replace
secondary switch.

Defective P.C.B
assembly.

Replace P.C.B
assembly.

Check continuity
of secondary
switch (with
door closed).

Check fan motor.

Check oven lamp.

Abnormal.

Abnormal.

Normal.

Defective fan
motor.

Defective fan
motor.

Replace fan
motor.

Replace fan
motor.

Loose connection.

Connection then
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.

Decrease in power
source voltage
with load.

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

Check the
power source
voltage.

Defective
magnetron.

Replace
magnetron.

NOTE: Simple test of power output-conducted by heating one liter water for one min. if available.

Minimum 8.5

o

C temperature rise is normal condition.

Summary of Contents for MS-1942G

Page 1: ...ICROWAVE OVEN SERVICE MANUAL MODEL MS 1942G CAUTION BEFORE SERVICING THE UNIT READ THE SAFETY PRECAUTIONS IN THIS MANUAL Website http biz lgservice com P NO 3828W5S3646 Mar 2004 Printed in Korea 삼 흥 정 판 ...

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: ... 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 SCHEMATIC DIAGRAM OF P C B 8 1 PRINTED CIRCUIT BOARD 8 2 P C B PARTS LIST 9 1 CONTENTS ...

Page 4: ...2 0 kg approx 13 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 turntable Roller Rest 1 1 ITEM MODEL Power Requirement Power Output Microwave Frequency Magnetron Timer Outside Dimensions Cavity...

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: ...or a desired time 5 CLOCK Used to set the time of day 6 START QUICK START One tap allows over to begin functioning 7 MICRO Used to select the desired power level for cooking 8 MORE LESS Used to change the cooking time desired weight 9 STOP CLEAR Used to stop over and clear all entries except time of day Oven Front Plate Window Door Screen Door Seal Display Window Control Panel Safety Door Lock Sys...

Page 8: ...rn to the last item entered or to the clock 3 QUICK START 4 MICROWAVE COOKING 5 MULTI STAGE MICROWAVE COOKING 1ST STAGE 2ND STAGE 6 AUTO DEFROST COOKING 7 CHILD LOCK 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 8 AUTO COOK STOP CLOCK CLOCK NUMBER START S...

Page 9: ...SCHEMATIC DIAGRAM 4 3 8 ...

Page 10: ... 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 high voltage diode and charging of the high voltage capacitor The negative 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 applie...

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: ...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 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 t...

Page 13: ...inal water temperature and the ambient temperature is 5 K The microwave power output P in watts is calculated from the following formula 4187 X T T 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 ...

Page 14: ...VAL 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 AIR DUCT 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 AS...

Page 15: ...ave energy must 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 Rem...

Page 16: ...NT 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 while making adjustmen...

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: ...EDURE 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 Filament terminal 2 Measure the resistance Ohm meter scale Rx1000 Filam...

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: ...owave Check for continuity of the fuse with an multi meter 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 Check for P C B connector Normal Abnormal 0 C Approx...

Page 21: ...istance Ohm meter scale R x 1000 Normal Abnormal or several Normal Approx 100 200 Abnormal or several 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 A B A C 40 60 300 500 ...

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: ...ing cooking cycle 11 Display time of day does not reappear 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 1 No input can be programmed Continuity No continuity Everything works as specified Still have trouble Defective PCB assembly Replac...

Page 24: ...ch with door closed Check continuity of primary switch with door opened Disconnect one side of the wire lead connected from transformer to the high voltage capacitor and operate the unit Replace fuse TROUBLE 2 Oven does not operate at all Display window does not display any figures and no input is accepted NOTE All these switches must be replaced at the same time Refer to page 5 6 5 7 2 Fuse does ...

Page 25: ...with door closed Check fan motor Check oven lamp Abnormal Abnormal Normal Defective fan motor Defective fan motor Replace fan motor Replace fan motor Loose connection Connection then 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 ...

Page 26: ...high voltage transformer 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 normal Abnormal Defective Protector Diode Replace Protector Diode Check Protector Diode TROUBLE 5 No m...

Page 27: ...e set power level Operates properly on HIGH CONDITION CHECK RESULT CAUSE REMEDY Output is full when you set lower power level Abnormal Disconnect the wire leads from relay 2 and check continuity relay 2 Operate the unit Defective P C B assembly Replace P C B assembly ...

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

Page 29: ...6 2 13581A 14970A 14026A 13552A 13213A 13352A 13720D 13536A DOOR PARTS EV ...

Page 30: ...6 3 23506A 23572A 268711 WTT021 24781S CONTROL PANEL PARTS EV ...

Page 31: ...6 4 33390G 35889A WTP013 WTT010 WTT021 33112U 36549S 33052A OVEN CAVITY PARTS EV ...

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

Page 33: ...6 6 56411A 568771 56930V 56324A 50FZZA 56201A 55900A WTT037 56549F WSZ062 WSZ002 54974S 50CZZH 56912B 948501 WTT028 WTT028 55262A 54810C WTT028 WSZ002 56851D 56901A INTERIOR PARTS EV ...

Page 34: ...6 7 56170D 63302A 65006B WTT028 WSZ002 63303A 948502 BASE PLATE PARTS EV ...

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