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MICROWAVE OVEN

SERVICE MANUAL
MODEL: LMVM1955SW
LMVM1955SB
LMVM1955SBQ
LMVM1955T
CAUTION
BEFORE SERVICING THE UNIT, READ THE
SAFETY PRECAUTIONS IN THIS MANUAL.
Website: http://us.lgservice.com

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Summary of Contents for LG LMVM1955SW

  • Page 1: Microwave Oven

    Website: http://us.lgservice.com MICROWAVE OVEN SERVICE MANUAL MODEL: LMVM1955SW LMVM1955SB LMVM1955SBQ LMVM1955T CAUTION BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
  • Page 2: Safety Precautions

    CAUTION SAFETY PRECAUTIONS PRECAUTIONS TO BE OBSERVED BEFORE AND DURING SERVICING TO AVOID POSSIBLE EXPOSURE TO EXCESSIVE MICROWAVE ENERGY a. Do not operate or allow the oven to be operated with the door open. b. Make the following safety checks on all ovens to be serviced before activating the magnetron or other microwave source, and make repairs as necessary;...
  • Page 3: Table Of Contents

    FOREWORD Read this Manual carefully. Failure to adhere to or observe the information in this Manual may result in exposing yourself to the Microwave Energy normally contained within the oven cavity. TABLE OF CONTENTS (Page) SAFETY PRECAUTIONS ......................Inside front page SPECIFICATIONS............................
  • Page 4: Specifications

    SPECIFICATIONS Rated Power Consumption..........1,400W maximum (Microwave oven+Cook top lamps+Ventilation fan) Microwave Output..............1170W (IEC 60705) Adjustable 117W through 1170W, 10 steps Frequency ................2,450 MHz 50 MHz Power Supply................120 VAC, 60 Hz Rated Current ...............12 Amp. (Microwave oven+Cook top lamps+Ventilation fan) Magnetron Cooling ...............Forced Air Cooling Rectification................Rectification Voltage Double Half-Wave Door Sealing .................Choke System Safety Devices..............Thermostat:...
  • Page 5: Cautions

    CAUTIONS Unlike other appliances, the microwave oven is MICROWAVE RADIATION high-voltage and high-current equipment. Personnel should not be exposed to the Though it is free from danger in ordinary use, microwave energy which may radiate from the extreme care should be taken during repair. magnetron or other microwave generating device if it is improperly used or connection.
  • Page 6: Installation

    INSTALLATION BEFORE YOU BEGIN, READ THE FOLLOWING INSTRUCTIONS COMPLETELY AND CAREFULLY. PRECAUTIONS ON INSTALLATION A. Plug the power supply cord into a 120V AC, 60Hz, single-phase power source with a capacity of 15A or 20A. B. Avoid placing the unit in a location where there is direct heat or splashing water.
  • Page 7: Operating Instructions

    OPERATING INSTRUCTIONS CONTROL PANEL...
  • Page 8: Control Panel Instructions

    CONTROL PANEL INSTRUCTIONS 1. DISPLAY: The Display includes a clock and 18. LIGHT TIMER: Touch this pad to set the light indicators to tell you time of day, cooking time timer. settings and cooking functions selected. 19. COOK TIME: Touch this pad followed by Number 2.
  • Page 9: Overall Circuit Diagram

    OVERALL CIRCUIT DIAGRAM SCHEMATIC DIAGRAM...
  • Page 10: Matrix Circuit For Touch Key Board

    MATRIX CIRCUIT FOR TOUCH KEY BOARD...
  • Page 11: General Information For Service

    GENERAL INFORMATION FOR SERVICE FEATURES AND SPECIFICATIONS GENERAL PRECAUTIONS IN USE FEATURES A. Never operate the unit when it is empty. Operating the oven with no load may shorten the A. The safety systems incorporated in this model are: life of the magnetron. Whenever cooking dry foods (1) Primary interlock switch (dried fish, bread, etc.) or a small amount of food, (2) Secondary interlock switch...
  • Page 12: Service Information

    SERVICE INFORMATION PRECAUTIONS AND REPAIR SERVICE TIPS PRELIMINARY (3) Do not operate the unit until it is completely A. SINCE NEARLY 2,100 VOLTS EXISTS IN SOME repaired, if any of the following conditions exist. CIRCUITS OF THIS UNIT REPAIRS SHOULD BE The unit must not be operated.
  • Page 13: Microwave Leakage Test

    MICROWAVE LEAKAGE TEST EQUIPMENT CAUTIONS • TESTER (VOLTS-DC, AC, Ohmmeter) • Be sure to check microwave leakage prior to servicing the oven if the oven is operative prior to • Microwave survey meter servicing. - Holaday HI-1500 • The service personnel should inform the HI-1501 manufacture importer, or assembler of any certified - Narda...
  • Page 14: Power Output Measurement

    MEASUREMENT WITH THE OUTER CASE NOTE WHEN MEASURING REMOVED (1) Do not exceed meter full scale deflection. (2) The test probe must be removed no faster than (1) When you replace the magnetron, measure for 1 inch/sec (2.5cm/sec) along the shaded area, microwave energy leakage before the outer case otherwise a false reading may result.
  • Page 15: Disassembly Instructions

    DISASSEMBLY INSTRUCTIONS IMPORTANT NOTES: (4) Remove 3 screws securing the circuit board. UNIT MUST BE DISCONNECTED FROM ELEC- TRICAL OUTLET WHEN MAKING REPAIRS, RE- PLACEMENTS, ADJUSTMENTS AND CONTIN- UITY CHECKS. WHEN RECONNECTING THE WIRE LEADS TO ANY PART, MAKE SURE THE WIRING CONNE- CTIONS AND LEAD COLORS ARE CORRECTLY MATCHED ACCORDING TO THE OVERALL CIR- CUIT DIAGRAM.
  • Page 16 B. REMOVING THE OUT CASE(Figure 4) (1) Remove the vent grille by removing two screws securing it to the out case. (2) Remove two screws securing it to the air duct. (3) Remove the mounting plate by turning the screws (1 or 2 screws) securing it to the out case.
  • Page 17 C REMOVING THE DOOR INTERLOCK SWITCHES (Figures 5, 6) (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 according to “ADJUSTMENT PROCEDURES” on page 7-11. Latch Board Latch Board Primary...
  • Page 18 D. REMOVING MAGNETRON E. REMOVING THE INVERTER MODULE (Figures 7 Through 8) (Figures 9 Through 11) (1) Remove the vent grille by loosening two screws. (1) Remove the vent grille by loosening two screws. (Figure 7) (Figure 7) (2) Remove the outcase. See page 7-5. (2) Remove the outcase.
  • Page 19 F. REMOVING STIRRER FAN G. REMOVING DOOR (Figure 14) (Figures 12 and 13) (1) Remove the vent grille by two screws securing it to (1) Remove one rivet securing it to oven upper plate the outcase loosening. by using knife blade. (2) Disconnect two leadwires.
  • Page 20 I. ASSEMBLING DOOR (3) Carefully pull the ventilation motor ASS'Y out of the microwave oven. (See Figure 17-b) (1) When mounting the door assembly to the oven assembly, be sure to adjust the door assembly parallel to the chassis. Also adjust so the door has no play between the inner door surface and oven frame assembly.
  • Page 21 L. REMOVING THE TURNTABLE MOTOR NOTES: • Remove the leadwire from the turntable motor VERY (1) Remove the glass tray and rotating ring. CAREFULLY. (2) Remove the turntable shaft VERY CAREFULLY • Be sure to grasp the connector not the wires when with hand.
  • Page 22: Interlock System

    INTERLOCK SYSTEM INTERLOCK MECHANISM The door lock mechanism is a device which has been specially designed to eliminate completely microwave activity when the door is opened during cooking and thus to prevent the danger resulting from the microwave leakage. ADJUSTMENT PROCEDURES CHECK THE DOOR LATCH AND SWITCH To avoid possible exposure to microwave energy CLOSING.
  • Page 23 TEST THE LATCH AND SWITCH SEQUENCE (5) Open the oven door slowly. Watch the door latch, (7) When you achieve the proper sequence of the Primary Switch. Release Rod and Lever on the switches in Steps 5 and 6, tighten the latch board switches to make sure they are zero to the body of screws at that point.
  • Page 24: Interlock Continuity Test

    INTERLOCK CONTINUITY TEST A. PRIMARY INTERLOCK SWITCH TEST B. SECONDARY INTERLOCK SWITCH TEST Disconnect the wire lead from the secondary When the door is opened slowly, an audible click switch. should be heard at the same time or successively Connect the ohmmeter leads to the common at intervals and the latches should activate the (COM) and normally open (NO) terminals of the switches with an audible click.
  • Page 25: Test And Checkout Procedures And Troubleshooting

    TEST AND CHECKOUT PRECEDURES AND TROUBLESHOOTING CAUTIONS 1. DISCONNECT THE POWER SUPPLY CORD FROM THE OUTLET WHENEVER REMOVING THE OUTER CASE FROM THE UNIT. PROCEED WITH THE TEST ONLY AFTER DISCHARGING THE HIGH VOLTAGE CAPACITOR AND REMOVING THE LEAD WIRES FROM THE INVERTER MODULE. 2.
  • Page 26 COMPONENTS TEST PROCEDURE RESULTS Antenna Gasket Chassis Filament 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. Touch Key board SENSOR Normal: Approximately 1.
  • Page 27 COMPONENTS TEST PROCEDURE RESULTS Measure the resistance. FAN MOTOR Normal: Approx. 50 ~ 150 ohms (Ohm-meter scale: R x 100) (Wire leads removed) Abnormal: Infinite or several B(BK) ohms. A(RD) C(WH) A-B: 76 ohms B-C: 22 ohms A-C: 96 ohms Measure the resistance.
  • Page 28: Checkout Procedures

    NOTES: • A MICROWAVE ENERGY 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 29 (2) CHECKOUT PROCEDURES FOR RELAY. - PROBLEM (A) - - PROBLEM (A) - FAN motor turns on without touching START key Oven lamp turns on without touching START key when the door is closed. when the door is closed. Remove the mate connector of I/O Remove the mate connector of I/O GOOD GOOD...
  • Page 30 (3) CHECKOUT PROCEDURES FOR CIRCUIT BOARD The following symptoms indicate a defective circuit 6) Wrong figures appear. board. 7) The figures of all digits. 1) The start function fails to operate but the high 8) Some of the indicators do no flicker light up. voltage Systems, the interlock switches, the door 9) The clock does not keep time properly.
  • Page 31: Troubleshooting

    C. TROUBLE SHOOTING WHEN YOU GET A COMPLAINT FROM YOUR CUSTOMER, EVALUATE THE COMPLAINT CAREFULLY. IF THE FOLLOWING SYMPTOMS APPLY, PLEASE INSTRUCT THE CUSTOMER IN THE PROPER USE OF THE MICROWAVE OVEN. THIS CAN ELIMINATE AN UNNECESSARY SERVICE CALL. CAUTIONS 1.
  • Page 32 (TROUBLE 1) The following visual conditions indicate a probable defective control circuit. 1. Incomplete segments. • Segment missing. • Partial segment missing. • Digit flickering (NOTE: Slight flickering is normal.) 2. Colon does not turn on or blink. 3. A distinct change in the brightness of one or more numbers in display. 4.
  • Page 33 (TROUBLE 2) Oven does not operate at all, Display window does not display any figures, and no input is accepted. CONDITION CHECK RESULT CAUSE REMEDY Malfunction of the Check continuity 1. Fuse blows. Continuity. Replace fuse, monitor switch. of monitor primary, monitor switch (with switches, and...
  • Page 34 (TROUBLE 3) Display shows all figures set, but oven does not start cooking while desired program times are set and START pad is touched. CONDITION CHECK RESULT CAUSE REMEDY Defective Replace Check continuity 1. Setting time No continuity. secondary switch. secondary switch.
  • Page 35 CONDITION CHECK RESULT CAUSE REMEDY Connect them Check the Abnormal Loose connection. 4. The display tightly. connection between shows F-4. sensor wire and control PCB. Normal Check the sensor. Abnormal Defective sensor. Replace sensor. Defective door or Replace door or Normal control PCB control PCB...
  • Page 36: Exploded View

    #EV# EXPLODED VIEW DOOR PARTS 13536A 13581A 13213A 13552A WTP004 14890A 13720D 14970A 14026A 14760A WTT029 WTT027 13806D 13651A...
  • Page 37 #EV# CONTROLLER PARTS (I) 268711 268771 268772 23506A...
  • Page 38 #EV# CONTROLLER PARTS (II) 24781M WTT028 268712 250201 24810P 23572A...
  • Page 39: Oven Cavity Parts

    #EV# OVEN CAVITY PARTS WTT029 WTT027 WTT029 34960A WTT027 33550P 33530A WTT021 WTT029 WTT027 34810Q 33112U 33390A 34930R 349311 330342 35026G WTP005 WTT022 535501 63302A 36912C 330341 35230A WTT025...
  • Page 40: Latch Board Parts

    #EV# LATCH BOARD PARTS 43500A 466001 WSZ085 43501A 466003 466001 44510A...
  • Page 41 #EV# INTERIOR PARTS (I) WTP015 552381 568711 56631A WTT034 33390G WTT028 WTT028 35889A 56549F WTT028 WSZ002 54974S 34351A 559002 WTT028 552382 WTT028 56324A WSZ002 55893A 50CZZH 35012A WTT028 36549S WTT028 WTP013 568772 340512 WTT028 53550F 56851H 53300B 340511...
  • Page 42 #EV# INTERIOR PARTS (II) WTP005 36549V WTP005 WTT024 WTT028 568774 568773 56930V 56501A 50FZZA 568776 56201A 535502 568775 WTT024 56411A 55262A 349312 568771 56549B 55231C...
  • Page 43 #EV# INSTALLATION PARTS 65862D 63300M 65862B 63861A...
  • Page 44: Schematic Diagram Of P.c.b

    SCHEMATIC DIAGRAM OF P.C.B 8-17...
  • Page 45: Printed Circuit Board

    PRINTED CIRCUIT BOARD 8-18...
  • Page 46 6920W2D010A RY15 6920WRD008A RELAY JQ1A-12V MATSUSHITA 250VAC 5A 12VDC 1A N 6920W2D010B 6920W5A012A RELAY G5G-1A-DT1-LG OMRON 250VAC 16A 12VDC 1A 6920WRD008A RELAY JQ1A-12V MATSUSHITA 250VAC 5A 12VDC 1A N 6920W2D010A 6920WRD008A RELAY JQ1A-12V MATSUSHITA 250VAC 5A 12VDC 1A N 6920W2D010B...
  • Page 47 Mar., 2003 P/NO : 3828W5S3018 Printed in Korea...

This manual is also suitable for:

Lmvm1955sbLmvm1955sbqLmvm1955tLmvm1955 series

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