LG LMV1825SB Service Manual Download Page 1

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MICROWAVE OVEN

SERVICE MANUAL

MODEL: LMV1825SB

BEFORE SERVICING THE UNIT, READ THE
SAFETY PRECAUTIONS IN THIS MANUAL.

LMV1825SW
LMV1825SBQ

CAUTION

website http://www.lgservice.com

Summary of Contents for LMV1825SB

Page 1: ...MICROWAVE OVEN SERVICE MANUAL MODEL LMV1825SB BEFORE SERVICING THE UNIT READ THE SAFETY PRECAUTIONS IN THIS MANUAL LMV1825SW LMV1825SBQ CAUTION website http www lgservice com ...

Page 2: ... proper alignment integrity and connections d Any defective or misadjusted components in the interlock monitor door seal and microwave generation and transmission systems shall be repaired replaced or adjusted by procedures described in this manual before the oven is released to the owner e A Microwave leakage check to verify compliance with the CSA Standard should be performed on each oven prior ...

Page 3: ...AM 5 1 MATRIX CIRCUIT FOR TOUCH KEY BOARD 5 2 GENERAL INFORMATION FOR SERVICE 6 1 GENERAL PRECAUTIONS IN USE 6 1 TRIAL OPERATION 6 1 FEATURES AND SPECIFICATIONS FEATURES 6 1 SERVICE INFORMATION 7 1 PRECAUTIONS AND REPAIR SERVICE TIPS 7 1 MICROWAVE LEAKAGE TEST 7 2 POWER OUTPUT MEASUREMENT 7 3 DISASSEMBLY INSTRUCTIONS 7 4 INTERLOCK SYSTEM 7 12 INTERLOCK CONTINUITY TEST 7 14 TEST AND CHECKOUT PROCED...

Page 4: ...ty Thermostat Open at 110 C 5 C Fuse 20A Primary Interlock Switch Secondary Interlock Switch Interlock Monitor Magnetron 2M248 High Voltage Capacitor Capacitor 1 0µF 2 1 KV AC High Voltage Diode Diode 350mA 9 0 KV Cook top Lamp 125 V 30 W Cavity Lamp 125 V 30 W Timer Digital up to 99 mim 99 sec in each cooking stage Tray Tempered Safety Glass Overall Dimensions 2915 16 W x167 16 D x155 8 H Oven Ca...

Page 5: ...area Proper 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 Unlike other appliances the microwave oven is high voltage and high current equipment Though it is free from ...

Page 6: ...d at all times In the event of an electrical short circuit grounding reduces the risk of electrical shock The plug must be plugged into an outlet that is properly installed and grounded BEFORE YOU BEGIN READ THE FOLLOWING INSTRUCTIONS COMPLETELY AND CAREFULLY WARNING Improper use of the grounding plug can result in a risk of electric shock Do not under any circumstances cut or remove the third gro...

Page 7: ...CONTROL PANEL 4 1 OPERATING INSTRUCTIONS 25 24 4 7 9 15 22 21 8 10 17 20 23 2 5 3 6 1 12 13 11 16 14 18 19 ...

Page 8: ... food 10 REHEAT Touch this pad to reheat casserole dinner plate and soup sauce The oven s sensor will tell the oven how long to cook depending on the amount of humidity coming from the food 11 NUMBER Touch number pads to enter cooking time power level quantities or weights 12 POWER LEVEL Touch this pad to select a cooking power level 13 TIME COOK Touch this pad to set a cooking time 14 STOP CLEAR ...

Page 9: ...5 1 SCHEMATIC DIAGRAM OVERALL CIRCUIT DIAGRAM ...

Page 10: ...TABLE ON OFF COOK POPCORN POTATO VEGETABLE VEGETABLE N C START WARM HOLD LEVEL CLOCK SET CUSTOM LIGHT HI LO OFF LESS LIGHT HI LO OFF VENT N C Ez On TIMER KITCHEN N C N C N C N C DEFROST AUTO TIME COOK 3 8 COOK 9 4 2 7 6 1 5 0 N C SENSOR SENSOR SENSOR SENSOR SENSOR SENSOR 13 11 12 9 10 8 1 2 3 4 5 6 7 ...

Page 11: ...y light comes on The unit will begin cooking and the display window will show the time counting down by seconds D After about 5 minutes make sure the primary interlock switch the secondary interlock switch and the interlock monitor switch operate properly by opening and closing the door several times Touch the START key each time the door is closed E Continue operating the unit Four long beep soun...

Page 12: ...All service adjustments should be made for minimum microwave energy leakage readings 3 Do not operate the unit until it is completely repaired if any of the following conditions exist The unit must not be operated a The door does not close firmly b The hinge is broken c The door seal is damaged d The door is bent or warped or there is any other visible damage on the unit that may cause microwave e...

Page 13: ...k 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 EQUIPMENT TESTER VOLTS DC AC Ohmmeter Microwave survey meter Holaday HI 1500 HI 1501 Narda 8100 8200 600 cc non conductive material beake...

Page 14: ... leakage not be more than 2 mW cm2 after determining that all parts are in good condition functioning properly and genuine replacement parts which are listed in this manual have been used 3 At least once a year have the electromagnetic energy leakage monitor checked for calibration by its manufacturer 1 Microwave power output measurement is made with the microwave oven supplied at its rated voltag...

Page 15: ...SPECIALLY SWITCHES AND HIGH VOLTAGE CIRCUIT A REMOVING POWER AND CONTROL CIRCUIT BOARD Figures 1 2 and 3 1 Remove a screw securing the control panel assembly to the oven cavity 2 Remove the control panel with pushing it upward 3 Remove the connector CN1 and wire leads Relay6 from the circuit board 4 Remove 3 screws securing the circuit board 5 Remove the FPC connector from the terminal socket foll...

Page 16: ... F P C connector into the terminal socket securely with the fingers 2 Hold the plastic fastener with thumb and forefinger of the other hand and push it slowly into the terminal socket Figure 6 NOTE When reconnecting the F P C connector make sure that the holes on the F P C connector are properly engaged with the hooks on the plastic fastener 3 Lock the level of the plastic fastener into the hook o...

Page 17: ...ng the screws 1 or 2 screws securing it to the out case 4 Remove two screws on the left central edge and one screws on the right central edge of Base plate Remove the Mount All from the out case by removing one screw securing it to the out case 5 Remove the outcase with disconnecting power cord connector Vent Grille Controller Door Mounting Plate 1 or 2 screws Out Case Mount All Figure 8 7 6 ...

Page 18: ... WH from cooktop lamp Secondary Interlock Switch Monitor Interlock Switch Primary Interlock Switch PK from P C B BL from P C B WH from H V Transformer RD from H V Transformer 7 7 C REMOVING THE DOOR INTERLOCK SWITCHES Figures 9 10 1 Disconnect the wire leads from the interlock switches 2 Remove two screws securing the Latch Board 3 Make necessary replacements and check microwave energy leakage acc...

Page 19: ...ULLY NOTES When removing the magnetron make sure that its dome does not hit any adjacent parts or it may be damaged When replacing the magnetron be sure to install the magnetron gasket in the correct position and be sure that the gasket is in good condition After replacing the magnetron check for microwave energy leakage with a survey meter Check microwave energy leakage must be below the limit of...

Page 20: ...k that the primary interlock switch the secondary interlock switch and the interlock monitor switch is in good operating normally After replacing the door check for microwave energy leakage with a survey meter Microwave energy leakage must be below the limit of 5mW cm2 With a 275 ml water load G DISASSEMBLING DOOR Figure 17 1 Remove the dielectric choke by using knife blade or small screw driver e...

Page 21: ...te by loosening mounting plate screws 1 or 2 screws securing it to the back plate See Figure 18 2 Remove MOUNT ALL loosening one screw loosening one screw securing the ventilation Motor and back plate See Figure 19 a 3 Carefully pull the ventilation motor ASS Y out of the microwave oven See Figure 19 b J REPLACING THE HUMIDITY SENSOR For sensor model only 1 Remove the sensor by removing two screws...

Page 22: ...ews securing it to the oven cavity Figure 21 4 Disconnect the leadwire from the turntable motor terminals 5 Remove the 2 screws securing the turntable motor to the oven cavity ASS Y Figure 22 NOTES Remove the leadwire from the turntable motor VERY CAREFULLY Be sure to grasp the connector not the wires when removing Wire Leads Turntable Motor 7 11 Figure 20 Figure 21 Figure 22 ...

Page 23: ...justment of the latch board may not be necessary Go to Steps 5 and 6 to check the sequence of the switches NOTE To correct sequence of the Primary Interlock Switch Secondary Interlock Switch and the Interlock Monitor Switch is very important If any gap is larger than 1 64 0 5 mm you will need to adjust the latch board Go to step 3 and follow all steps in order ADJUST THE LATCH AND SWITCH CLOSING 3...

Page 24: ...ro to the body of the switches in the following sequence Interlock Monitor Switch Primary Interlock Switch Secondary Interlock Switch NOTE The Interlock Monitor Switch is an added safety check on the Primary and Secondary Interlock Switches If the Primary and Secondary Interlock Switches allow the oven to operate with the door open the Monitor Switch will blow the fuse 7 When you achieve the prope...

Page 25: ... 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 a closed circuit in the door open condition When the door is closed the meter sho...

Page 26: ... each filament terminal of the magnetron and the chassis ground with an ohm mater on high test scale 1 Measure the resistance With an ohm meter on Rx1 scale a Primary winding b Filament winding c Secondary winding 2 Measure the resistance With an ohm meter on highest scale a Primary winding to ground b Filament winding to ground Normal reading Less than 1 ohm Normal reading Infinite ohms NOTE Repl...

Page 27: ...tinuity 1 Forward Ohm meter Figure 26 a 1 Reverse Ohm meter Figure 26 b Normal reading Momentarily indicates several ohms and then gradually returns to infinite ohms Abnormal reading Indicates continuity or infinite ohms from the beginning Normal readings Infinite Abnormal reading Indicates continuity Normal readings continuity Abnormal reading Infinite Normal readings Infinite Abnormal reading co...

Page 28: ...SOR SENSOR SENSOR SENSOR SENSOR SENSOR SENSOR SENSOR SENSOR SENSOR 13 13 11 11 12 12 9 10 10 8 1 2 3 4 5 6 7 1 2 3 BK RD WH Measure the resistance between terminal pins of connector KEY CONNECTOR NOTE When reconnecting the FPC connector make sure that the holes on the FPC connector are properly engaged with hooks on the plastic fastener MATRIX CIRCUIT FOR TOUCH KEY BOARD CONNECTOR KEY CON 7 17 COM...

Page 29: ... switches and or the interlock monitor switch Malfunction of the high voltage transformer the high voltage capacitor including the diode the magnetron the blower motor or the circuit board PROBLEMS CAUSES 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 NOTES If the fuse is blown by an i...

Page 30: ...ll operate GOOD Replace the circuit board Replace RELAY1 PROBLEM B FAN motor and oven lamp turn on When the door is closed and START key is touched Measure the voltage at pin NO 35 of U01 Voltage reading 0 Vdc 10 of U03 Voltage reading about 15V Replace the circuit board Defective RELAY1 or poor connection of RELAY1 Defective RELAY1 Replace RELAY1 or correct the connection NO NO YES YES NO NO YES ...

Page 31: ...he interlock switches the door sensing and the relay check good 2 The unit with a normal relay continuously operates 3 Proper temperature measurement is not obtained 4 The buzzer does not sound or continues to sound 5 Some segments of one or more digits do not light up or they continue to light up or segments light when they should not 6 Wrong figures appear 7 The figures of all digits 8 Some of t...

Page 32: ...PERATION on page 6 1 DISPLAY Problems A thru C HELP UP Problems D thru E BUZZER Problems F Measure voltage between pin 1 and pin 3 of connector CN1 Measure resistance of touch key board after removing connector S1 See page 7 4 and 7 17 0 120 120V Replace circuit board Normal circuit board Normal resistance Voltage incorrect Normal resistance Resistance incorrect Replace touch key board Normal touc...

Page 33: ... connector S1 Contact OK Replace Circuit board Correct seating Normal circuit board Normal contact Poor contact Normal Primary switch No continuity Adjust or replace door sensing switch Measure resistance of H V capacitor see page 7 16 Resistance incorrect Normal resistance Measure resistance of fan motor Terminal A C 140 to 150 ohm Terminal A B 25 to 40 ohm Resistance incorrect Replace fan motor ...

Page 34: ... H V C Abnormal Replace H V D Normal Magnetron Replace Magnetron Normal Normal H V D Check the continuity of H V D see page 7 16 Replace H V C Normal resistance Replace H V T Normal resistance NO continuity Replace circuit board Normal circuit board Poor contact Replace circuit board Normal circuit board Contact OK Normal contact Correct seating Check contact of connector S1 Check the contact of r...

Page 35: ...7 24 PROBLEM F No buzzing when touching the key between stages or at end of cooking 1 Normal circuit board Check normal operation circuit board Replace circuit board Runs ...

Page 36: ...e magnetron thermal fuse and oven thermostat Poor contact Replace circuit board Normal circuit board Contact OK Normal contact Correct seating Check contact of connector S1 see page 7 4 Replace ventilation motor ASS Y NO runs Normal ventilation motor ASS Y Check the contact of magnetron thermal fuse and oven thermostat Runs Runs Runs Runs ...

Page 37: ...8 1 EXPLODED VIEW DOOR 13581A 13552A WTP004 13536A 13213A 14760A 13720D 13650A WTT028 14890A 14970A 14026A ...

Page 38: ...8 2 CONTROL PANEL 24781M 24810P 268711 WTP018 07 23506A ...

Page 39: ...8 3 OVEN CAVITY 33530A 34960A 33550P WTT021 WTT027 WTT029 WTT028 WTT029 WTT027 33112U WTT022 34810Q 34930R 330342 535501 35230A WTT022 63302A 56804A 368771 63303A 36912C WTT022 330341 35026G ...

Page 40: ...8 4 LATCH BOARD 466001 43501A 43500A 466003 466001 44510A WSZ084 ...

Page 41: ...8 5 INTERIOR I 33390G 34370T 35889A 33052A 55892A 53550F 340511 54930F WTT021 56930G WSZ002 WTP013 53300B WSZ002 WTP002 56170D WSZ002 56851D 50CZZH WTT021 54810C 55238A WSZ002 56324A 36549S 568772 ...

Page 42: ...8 6 INTERIOR II WTT028 56501A 56930V 55231C 01 568771 WTT028 56549F 55262A WTT034 36549V 56912B WTP004 WSZ002 WTT029 535502 56411A 55900A 33700A 56804A 56901A 02 04 50FZZA WTP013 56820A ...

Page 43: ...8 7 INSTALLATION WSZ133 44360A WSZ098 WWZ068 WWZ068 WSZ204 56411A 65862D 63300M 63861A WSZ203 WSZ136 65862B ...

Page 44: ...TART WARM WARM HOLD HOLD LEVEL LEVEL CLOCK CLOCK SET SET CUSTOM CUSTOM LIGHT LIGHT HI LO OFF HI LO OFF LESS LESS LIGHT LIGHT HI LO OFF HI LO OFF VENT VENT N C N C Ez On Ez On TIMER TIMER KITCHEN KITCHEN N C N C N C N C N C N C N C N C DEFROST DEFROST AUTO AUTO TIME TIME COOK COOK 3 8 COOK COOK 9 4 2 7 6 1 5 0 N C N C SENSOR SENSOR SENSOR SENSOR SENSOR SENSOR SENSOR SENSOR SENSOR SENSOR SENSOR SENS...

Page 45: ...8 15 PRINTED CIRCUIT BOARD ...

Page 46: ...P NO 3828W5S3224 May 2003 Printed in Korea ...

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