LG MH-1446SQP Service Manual Download

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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 operating 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.

Continuity

No continuity

Check the con-
nection between
CN1 connector
and PCB
assembly.

Defective
secondary switch.

Replace
secondary switch.

Defective PCB
assembly.

Replace PCB
assembly.

Check continuity
of secondary
switch (with
door closed).

Check fan motor.

Check oven lamp.

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.

Abnormal.

Measure the
output power.

Disconnect the
wire leads from
relay 2 and
check on and off
time with
multitester.

Defective PCB
assembly.

Replace PCB
assembly.

Decrease in power
source voltage
with load.

Suggest customer
contact local
electric power
utility company
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˚C temperature rise is normal condition.

Summary of Contents for MH-1446SQP

Page 1: ...BEFORE SERVICING THE UNIT READ THE SAFETY PRECAUTIONS IN THIS MANUAL Website http biz lgservice com 삼 흥 정 판 MICROWAVE OVEN SERVICE MANUAL MODEL MH 1446SQP 삼 흥 정 판 P NO MFL36414401 October 2006 Printed in Korea ...

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: ...ox Touch Control System Clock 1 00 12 59 Microwave Power for Variable Cooking Power level HIGH Full power throughout the cooking time 9 Saute approx 90 of Full power 8 Reheat approx 80 7 Med High approx 70 6 Medium approx 60 5 Med Low approx 50 4 Defrost approx 40 3 Low approx 30 2 Simmer approx 20 1 Warm approx 10 Owner s manual Glass turntable Roller rest Grill rack ITEM MODEL Power Requirement ...

Page 5: ... operation of the microwave oven requires that the magnetron 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 fro...

Page 6: ...nal surface unit or above a conventional wall oven 5 Use microwave oven in an ambient temperature less than 104 F 40 C 6 Place the microwave oven on a sturdy and flat surface at least 10 cm 4 inches from the wall 7 Place the microwave oven as far away as possible from TV RADIO COMPUTER etc to prevent interference GROUNDING INSTRUCTIONS For personal safety this appliance must be fully grounded at a...

Page 7: ...d 6 Q DEFROST 7 MICRO Used to cook food for a desired time 8 COMBI Used to cook food by microwave and combination 9 GRILL Used to cook food by microwave and grill 10 HOLD WARM 11 POWER Used to select power level for cooking 12 CLOCK Used to set the time of day 13 STOP CLEAR Used to stop oven and clear all entries except time of day 14 START ADD 30 SECOND One tap allows oven to begin functioning Ro...

Page 8: ...OOKING 1ST STAGE 2ND STAGE 7 AUTO WEIGHT DEFROST COOKING 8 CHILD LOCK This oven has a CHILD LOCK feature TO SET CHILD LOCK Touch the pad Touch and hold PARAR BORRAR pad LOCK appear on the display TO CANCEL CHILD LOCK Touch the pad Touch and hold PARAR BORRAR pad LOCK disappears 9 GRILL COOKING 10 COMBI COOKING PARAR BORRAR RELOJ RELOJ NUMBER Más 30 Seg PARAR BORRAR PARAR BORRAR TIME POTENCIA NUMBE...

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

Page 10: ...tive 4000 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 vo...

Page 11: ...d vent openings for microwave leakage Check for microwave leakage after every servicing The power density of the microwave radiation leakage emitted by the microwave oven should not exceed 4 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 1...

Page 12: ... deflection The 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 is mov...

Page 13: ...put 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 measuring the final water temperature S...

Page 14: ... up and push the door NOTE 1 After replacing the door be sure to check that the primary switch monitor switch and secondary switch operate normally 2 After replacing the door check for microwave energy leakage with a survey meter Microwave energy must be below the limit of 4 mW cm2 with a 275 ml water load 3 When mounting the door assembly to the oven assembly be sure to adjust the door assembly p...

Page 15: ... 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 G REMOVING THE TURNTABLE MOTOR 1 Remove the turntable and rotating ring 2 Lay the unit down on its back 3 Remove the turntable motor cover The turntable base cover is easily removed by pinching t...

Page 16: ...arth screw K INTERLOCK SYSTEM 1 INTERLOCK MECHANISM The door lock mechanism is a device which has been specially designed to eliminate microwave activity when the door is opened during cooking and thus to prevent the danger resulting from the microwave leakage 2 MOUNTING OF THE PRIMARY MONITOR SECONDARY SWITCHES TO THE LATCH BOARD 3 INSTALLATION AND ADJUSTMENT OF THE LATCH BOARD TO THE OVEN ASSEMB...

Page 17: ...losed 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 open...

Page 18: ...N COMPONENTS TEST PROCEDURE RESULTS HIGH VOLTAGE TRANSFORMER 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 resista...

Page 19: ... 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 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 ...

Page 20: ...with an Multi meter Normal Gill heater Approx 15 Ω at 20 30oC Normal more than 1 0M Ω NOTE Make sure heater is fully cooled when tested NOTE If the fuse is blown check primary the secondary 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 ...

Page 21: ...CED 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 POWER LEVEL 1 2 3 4 5 6 7 8 9 10 4 sec 6 sec 8 sec 10 sec 12 sec 14 sec 16 sec 18 sec 20 sec 22 sec 18 sec 16 sec 14 sec 12 sec 10 sec 8 sec 6 sec 4 sec 2 sec 0 sec Relay 2 A B Measure the resistance Ohm meter scale R x 1 Check for continu...

Page 22: ...s panel to discharge any static charge built up in your body Micom model only CONDITION Microwave oven does not work Inserting many plugs into one outlet and using them at the same time blown fuse or breaker 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 Inc...

Page 23: ... does not turn on after setting cooking cycle 11 Display time of day does not reappear when cooking is finished 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...

Page 24: ...itor secondary switches and RELAY RY2 of P C B Assembly 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 fuse primary monitor secondary switches and RELAY RY2 of P C B Assembly Check continuity of monitor switch with door closed Check ...

Page 25: ...with door closed Check fan motor Check oven lamp Abnormal 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 mul...

Page 26: ...e leads from relay 2 and check continuity of relay 2 Operate the unit Normal Normal Abnormal Defective high voltage capacitor Replace high voltage capacitor Check high vol tage capacitor Abnormal Defective high voltage transformer Replace high voltage transformer Check high vol tage transformer Abnormal Defective high voltage diode Replace high voltage diode Check high vol tage diode Normal Abnorm...

Page 27: ...rmal Normal Normal Heater Thermostat and relay3 Grill Abnormal Malfunction the thermostat Malfunction the heater Replace Wire connection No continuity Open or loosen Replace or connect tightly Replace 1 Lower tempera ture the oven Abnormal Normal Heater Thermostat and relay3 Grill Abnormal Malfunction the thermostat Malfunction the heater Replace Replace NOTE Make sure the wire leads are in the co...

Page 28: ...6 1 EXPLODED VIEW INTRODUCTION MODEL MH 1446SQP EV ...

Page 29: ...6 2 13213A 13552A 15006A 13581A 13536A 14026A 14970A 13720D 14890A DOOR PARTS EV ...

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

Page 31: ...6 4 35889A 33052M 36549S 35300A 33390G 35026G 33112U 44360A WTP013 WNH001 348101 348101 WTT021 WTT010 348102 WTP004 34980A OVEN CAVITY PARTS EV ...

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

Page 33: ... 6 568771 WSZ002 WSZ002 WSZ002 WSZ002 WEB001 WTT028 56411A 56930V 56549F 54974S WTT037 55900A 54810C WTT028 50CZZH 34930W 56912B 55262A 948501 56324A 56851D WEB001 50FZZA 56201A 35012A INTERIOR PARTS EV ...

Page 34: ...6 7 WTT021 63302A 63303A 56170D WSZ002 948502 65006B BASE PLATE PARTS EV ...

Page 35: ......

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