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LG LMC1575BD, Service Manual

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SAFETY PRECAUTIONS  ------------------------------------------------------------------------------------------------------------------------------------------  Inside front cover
SPECIFICATIONS  ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------  1-1
CAUTIONS  -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------  2-1 
INSTALLATION  ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------  3-1
OPERATING INSTRUCTIONS  ---------------------------------------------------------------------------------------------------------------------------------------------------------  4-1

FEATURES ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------  4-1
CONTROL PANEL --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------  4-1
OPERATING SEQUENCE ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------  4-2
SCHEMATIC DIAGRAM ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------  4-4
CIRCUIT DESCRIPTION -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------  4-5

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 ------------------------------------------------------------------------------------------------------------------------------------------------------------------  5-4
INTERLOCK CONTINUITY TEST ----------------------------------------------------------------------------------------------------------------------------------------------------------------------  5-9
COMPONENT TEST PROCEDURE -----------------------------------------------------------------------------------------------------------------------------------------------------------------  5-10
TROUBLE SHOOTING -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------  5-12
Trouble shooting for inverter PCB ---------------------------------------------------------------------------------------------------------------------------------------------------------------------  5-18

EXPLODED VIEW  --------------------------------------------------------------------------------------------------------------------------------------------------------------------------  6-1

CONTENTS

Summary of Contents for LMC1575BD

Page 1: ...ronics entity from which you received this Service Manual The material covered by this prohibition includes without limitation any text graphics or logos in this Service Manual CAUTION BEFORE SERVICING THE UNIT READ THE SAFETY PRECAUTIONS IN THIS MANUAL LMC1575BD LMC1575ST LMC1575SW LMC1575SB P NO MFL69902602 MODEL MICROWAVE OVEN SERVICE MANUAL February 2017 Printed in Korea Copyright 2017 LG Elec...

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: ...QUENCE 4 2 SCHEMATIC DIAGRAM 4 4 CIRCUIT DESCRIPTION 4 5 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 4 INTERLOCK CONTINUITY TEST 5 9 COMPONENT TEST PROCEDURE 5 10 TROUBLE SHOOTING 5 12 Trouble shooting for inverter PCB 5 18 EXPLODED VIEW 6 1 CONTENTS ...

Page 4: ... 21 7 16 x 12 1 8 x 17 54 4 cm x 30 8 cm x 43 2 cm Cavity Dimensions W x H x D 15 9 16 x 10 5 16 x 16 39 5 cm x 26 2 cm x 40 6 cm Net Weight 27 5 lbs approx 12 5 kg approx Shipping weight 32 lbs approx 14 5 kg approx Control Complement Touch Control System Microwave Power for Variable Cooking Power level 100 90 80 70 60 50 40 30 20 10 Rating Label Location Accessories Manual Shaft Glass turntable ...

Page 5: ...d front plate of the oven cavity NEVER put iron tools on the magnetron NEVER put anything into the latch hole and the interlock switches area MICROWAVE RADIATION Personnel should not be exposed to the microwave energy which may radiate from the magnetron or other microwave generating device if it is improperly used or connection All input and output microwave connections waveguide flange and gaske...

Page 6: ...ouch circuitry because it has very hot high voltage circuitry Even when replacing board extreme care should be taken to avoid possible electric shock hazards High voltage charge may remain in circuits 4 Do not touch aluminum heat sink because it is energized very high voltage and it is very hot in high heat energy 5 Do not test oven while inverter grounding screw is loose It is very dangerous to o...

Page 7: ...ture 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 Bluetooth equipment or Wi Fi devices etc to prevent interference 10cm PREFERRED METHOD ENSURE PROPER GROUND EXISTS BEFORE USE TEMPORARY METHOD ADAPTER PLUGS NOT PERMITTED IN CANADA ALIGN LARGE PRONGS SLOTS ...

Page 8: ...4 1 FEATURES OPERATING INSTRUCTIONS ...

Page 9: ...od by weight 7 POWER LEVEL The microwave oven is equipped with 10 power levels for maximum flexibility and control over cooking The Microwave Power Levels section contains suggestions for which power level to use when preparing various foods 8 COOK TIME Touch this key to manually set a desired cook time 9 TIMER ON OFF Touch this key to set a kitchen timer 10 MORE LESS Set cooking time and weight L...

Page 10: ...reduced to 90 1 2 and then the output power will be reduced from 90 to 70 for 6minutes gradually 1 3 and then 70 will be kept on 2 If the power level starts at 90 the level will be kept till 1minute and then reduced to 70 gradually 3 Power output reduction Continues using condition Continues using make inverter overheating To protect inverter PCB from overheating Inverter detect temperature itself...

Page 11: ...4 4 SCHEMATIC DIAGRAM ...

Page 12: ... noise preventing choke coils The inverter PCB generates high voltage of approximately 4 000V negative DC The voltage is applied to the filament of the magnetron WHEN THE OVEN IS SET AT POWER LEVEL The inverter control micro wave out put power from 100 to 30 by controlling power consumption 20 and 10 Power are controlled by relay on off working One complete cycle of relay 32 seconds WHEN THE DOOR ...

Page 13: ...tain the cause of the excessive leakage The service personnel should instruct the owner not to use the unit until the oven has been brought into compliance If the oven operates with the door open the service personnel should Tell the user not to operate the oven Contact the manufacturer The service personnel should check all surface and vent openings for microwave leakage Check for microwave leaka...

Page 14: ...ed meter full scale deflection The test probe must be moved 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 by 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 t...

Page 15: ...et 5 Total time T can be obtained by repeat testing in other to raise the water temperature 10 C 0 2 For the measurement of the heating up time of the magnetron filament can be used in conjunction with an oscilloscope t is heating time excluding the magnetron filament heating up time The MWO is operated Stop watch is used to count total time And Energy consumption Wh should be measured from start ...

Page 16: ...he ground terminal C CONTROL PANEL ASSEMBLY 1 Open the door 2 Disconnect the lead wire from RELAY and all connectors of the PCB SUB ASSEMBLY 3 Remove one screw on top and behind control panel and Lift up and pull out control panel assembly carefully from the cavity D PCB ASSEMBLY REMOVAL 1 Remove the control panel assembly from the cavity Refer to control panel assembly removal on previous step 2 ...

Page 17: ...p 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 par...

Page 18: ...unting screws properly making sure there is no gap between the waveguide and the magnetron 4 Magnetron is hot after operation of oven H REMOVING THE TURNTABLE MOTOR 1 Remove the turntable rotating ring and shaft 2 Lay the unit down on its back 3 Remove the turntable motor cover The turntable base cover is easily removed by pinching the eight parts with a wire cutting 4 Disconnect the leadwire from...

Page 19: ...SS Y 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 PRIMARY SWITCH MONITOR SWITCH SECONDARY SWITCH 2 INSTALLATION AND ADJUSTMENT OF THE LATCH BOARD TO THE OVEN ASSEMBLY Mount the latch board to the...

Page 20: ...er supporter both side using Flat blade screwdriver 2 Remove the screw and washer using Phillips screwdriver 3 Push the inverter backward and remove the inverter LMC1575BD 00 LMC1575ST 00 LMC1575SW 00 LMC1575SB 00 LMC1575BD 01 LMC1575ST 01 LMC1575SW 01 LMC1575SB 01 ...

Page 21: ...tch 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 indicate an open cir...

Page 22: ... 3 High voltage diode Open short test Normal More than 0 4V Abnormal Less than 0 4V or open MAGNETRON Wire leads removed 1 Measure the resistance Ohm meter scale Rx1 Filament terminal 2 Measure the resistance Ohm meter scale Rx1000 Filament to chassis Normal Less than 1 ohm Normal Infinite NOTE Check Magnetron and Inverter PCB at same time Magnetron and inverter interact to each other Defect of ma...

Page 23: ...ohm TURNTABLE MOTOR Wire leads removed Measure the resistance Ohm meter scale R x 1 Normal Approx 115 130 ohm Abnormal Infinite or several ohm 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 Antenna Gasket Chas...

Page 24: ...sing tester If sensor open exchange sensor 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 ...

Page 25: ...INATE AN UNNECESSARY SERVICE CALL 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 Inconsistent intensity of microwave by their ch...

Page 26: ...PCB can not receive any touch button signal then Error F 3 is displayed CONDITION CHECK RESULT CAUSE REMEDY Everything works as specified Continuity No continuity Still have trouble Defective Door assembly 1 Defective PCB assembly 2 Defective Door harness Loose connection Defective PCB assembly Replace Door assembly 1 Replace PCB assembly 2 Replace Door Connect them tightly Replace PCB assembly Re...

Page 27: ...PCB No continuity Defect inverter Replace inverter Defect magnetron Abnormal Replace magnetron Malfunction of the monitor switch Replace fuse Latch board assembly and main PCB Check continuity of monitor switch with door closed Check continuity of primary switch with door opened check inverter refer page 5 15 Check magnetron Replace fuse Continuity Malfunction of secondary switch Replace fuse Latc...

Page 28: ...oking while desired program times are set and START button is touched CONDITION CHECK RESULT CAUSE REMEDY Continuity Continuity Abnormal No continuity Abnormal Defective oven lamp Replace oven lamp Normal No continuity Defective PCB assembly Defective secondary switch Defective fan motor Loose connection Replace PCB assembly Replace Latch board assembly Replace Latch board assembly Connect them ti...

Page 29: ...er to protect inverter from overheating Defective magnetron Decrease in power source voltage with load Defective PCB assembly Reinstall Replace magnetron Suggest customer contact local electric power utility co or qualified electrician Replace PCB assembly Check install Condition Measure the output power Check the power source voltage Check the inverter PCB Output is low NOTE Simple test of power ...

Page 30: ...on Defective magnetron Replace Connect wire on Magnetron Replace magnetron Check inverter PCB Check wiring on Magnetron Check magnetron No microwave oscillation NOTE 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 When removing the magnetron be sure to install the magnetron gasket in the correct position ...

Page 31: ...oader Connector Comm Connector H V Capacitor H V Transformer Resonant capacitor Earth wire High Voltage Diode MGT Output Shunt resistor Inverter PCB TOP view Inverter PCB BOTTOM view Inverter PCB Most Check Points Communication Connector CN3 AC Terminal L N Bridge Diode D5 IGBT Q1 Zener Diode ZD201 Temp Thermistor TH91 High Voltage Diode D8 D9 LMC1575BD 00 LMC1575ST 00 LMC1575SW 00 LMC1575SB 00 LM...

Page 32: ...de air flow If the supporter is not assembled correctly air flow is not good on inverter PCB Bad Air flow make inverter PCB overheating or F 16 error Check a earth wire through the hole Check 4 points of the hook both sides LMC1575BD 00 LMC1575ST 00 LMC1575SW 00 LMC1575SB 00 ...

Page 33: ...ir flow If the supports is not correctly assembled air flow is not good on the inverter PCB Bad air flow causes PCB overheating or F 16 Error code Check a earth wire through the hole Check 4 points of the hook both sides LMC1575BD 01 LMC1575ST 01 LMC1575SW 01 LMC1575SB 01 ...

Page 34: ... harness status on Connector of PCB 4 After cooling down Inverter PCB check resistance value of TH91 5 If resistance value is not 15K 18Kohm at room temperature exchange inverter PCB F 13 Inverter Over Current 1 Check Fan motor status The wind blows 2 Check MGT status Magnet crack Antenna Gasket burnt mark 3 Check communication harness status on Connector of PCB 4 Check inverter PCB step 1 AC conn...

Page 35: ...stance Q1 ZD201 Single Ended Resonant Circuit 3 5 IGBT Gate Driver Magnetro n Input Current Sensing MCU B D Temp Writing RX TX Main Comm SMPS PCB High Voltage Circuit Themistor Circuit Reset Regulator 15V 5V CT Trigger PT Circuit Rectifier Circuit Surge Protection L N L N AC 127V 60Hz Fuse Holder Input Voltage Sensing F_CN1 F_CN2 GND Resonant Voltage Sensing SMPS Inverter PCB Earth CN3 Symptom Not...

Page 36: ... TH91 Symptom Not heating F 11 Check Connection Open Short CN3 CN8 Symptom Not heating F 19 Check Resistance Q1 ZD201 Symptom Dead Check Open Short Symptom Not heating F 13 F 14 F 15 F19 Check Open Short D5 Symptom Not heating F 13 F 14 F 15 F 19 Check Open Short D8 D9 LMC1575BD 01 LMC1575ST 01 LMC1575SW 01 LMC1575SB 01 ...

Page 37: ...r earth wire If earth is loose or not fixed inverter work not correctly and make current leakage Make sure earth wire fix correctly after change inverter PCB Communication wire connector If this wire is not connect exactly it make F 11 Error code AC power connector If this wire is not connect exactly it make F 13 14 and 15 Error code ...

Page 38: ... Tester mode Beep mode Status Test result normal Open OL Abnormal Short Beep Check Connector pin CN3 CN8 Inverter CN3 6 7 pin Main CN8 1 2 pin Example normal Open Example abnormal Short LMC1575BD 00 LMC1575ST 00 LMC1575SW 00 LMC1575SB 00 ...

Page 39: ... Abnormal 0 4V or short Example normal Check TH91 Thermistor Example abnormal Short or Open Tester mode Beep or resistance mode Status Test result Normal 20Kohm Room temperature Abnormal Open or Short Thermistor TH91 17 42Kohm Room temperature 23 3 Example normal 2 F 16 or F 17 Inverter PCB Check 3 F 13 or F 14 or F 15 Inverter PCB Check Example abnormal Short Example abnormal Short Example normal...

Page 40: ... 10Kohm Abnormal 10Kohm or short Check D5 Bridge Diode D8 D9 High Voltage Diode Check Q1 IGBT Bridge Diode AC Checking Bridge Diode DC Checking HVD D8 D9 Short Checking Example normal Example normal Example normal Open Example abnormal Short Example abnormal Short Tester mode Beep mode Status Test result Normal Open OL Abnormal Short Beep LMC1575BD 00 LMC1575ST 00 LMC1575SW 00 LMC1575SB 00 D9 D8 E...

Page 41: ...key and Start key double key For damaged IC test Check the resistance value of IC Pin and ground using tester If all tests are OK see again Error Code Case page Normal levels of resistance value 10 difference Normal OK Short or 10 difference Abnormal NG Normal Level Resistance 1 5V DC 4 2Kohm 2 pin 2 15V DC 4 8Mohm 4 pin 3 Temp AD 15 20Kohm 6 pin It may differ slightly depending on the tester LMC1...

Page 42: ... Tester mode Beep mode Status Test result Normal Open OL Abnormal Short Beep Check Connector pin CN3 CN8 Inverter CN3 6 7 pin Main CN8 1 2 pin Example normal Open Example abnormal Short LMC1575BD 01 LMC1575ST 01 LMC1575SW 01 LMC1575SB 01 ...

Page 43: ...Abnormal 0 4V or short Example normal LMC1575BD 01 LMC1575ST 01 LMC1575SW 01 LMC1575SB 01 Check TH91 Thermistor Example abnormal Short or Open Tester mode Beep or resistance mode Status Test result Normal 20Kohm Room temperature Abnormal Open or Short Thermistor TH91 17 96 Kohm Room temperature 23 3 Example normal 2 F 16 or F 17 Inverter PCB Check 3 F 13 or F 14 or F 15 Inverter PCB Check Example ...

Page 44: ... 10Kohm Abnormal 10Kohm or short Check D5 Bridge Diode D8 D9 High Voltage Diode Check Q1 IGBT Bridge Diode AC Checking Bridge Diode DC Checking HVD D8 D9 Short Checking Example normal Example normal Example normal Open Example abnormal Short Example abnormal Short Tester mode Beep mode Status Test result Normal Open OL Abnormal Short Beep LMC1575BD 01 LMC1575ST 01 LMC1575SW 01 LMC1575SB 01 D9 D8 E...

Page 45: ...nd ground using tester If all tests are OK see again Error Code Case page Normal levels of resistance value 10 difference Normal OK Short or 10 difference Abnormal NG Normal Level Resistance U1 MICOM R51076C Renesas 15 20Kohm 2 Pin U1 MICOM R51076C Renesas 4 5Kohm 10 Pin U6 Gate driver IC 2EDL05I06PF Infineon 1 0Mohm U7 OP AMP SN358 AUK 4 5Kohm U8 Dual comparator KIA393F KEC 1 0Mohm It may differ ...

Page 46: ...5 34 Inverter supporter upper type Inverter supporter lower type A B C D E ...

Page 47: ... LMC0975 LMC1375 LMC1575 LMC2075 inverter supporter upper inverter supporter lower Pro inverter supporter upper Pro inverter supporter lower inverter Pro inverterMGT harness ferrite core A D C E B D B D B D ...

Page 48: ...EXPLODED VIEW EV INTRODUCTION MODEL Old Inverter Customer Model Product Code SVC Model New Pro Inverter Customer Model Product Code SVC Model ...

Page 49: ...DOOR PARTS EV 1005 1000 1004 1002 1007 1006 1384 1114 ...

Page 50: ...CONTROL PANEL PARTS EV 2006 2002 2000 2001 2004 ...

Page 51: ...OVEN CAVITY PARTS EV 3001 3034 3002 3012 3009 3161 W607 3008 ...

Page 52: ...LARCH BOARD PARTS EV 4001 NSP No Service Parts W509 ...

Page 53: ...INTERIOR PARTS EV 5003 5014 5041 5007 5012 5010 W520 W140 5001 5016 5009 5006 W101 W101 5004 5011 ...

Page 54: ...BASE PLATE PARTS EV 5474 6100 6007 6011 5473 W520 507V 5471 5472 6001 W701 ...

Page 55: ......

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