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LG LRM1250W Service Manual

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Website http://us.lgservice.com
MICROWAVE OVEN
SERVICE MANUAL
MODEL: LRM1250W
CAUTION
BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
February, 2005
P/NO : 3828W5S5129
Printed in Korea

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  • Page 1 Website http://us.lgservice.com MICROWAVE OVEN SERVICE MANUAL MODEL: LRM1250W CAUTION BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL. February, 2005 P/NO : 3828W5S5129 Printed in Korea...

  • Page 2: Safety Precautions

    SAFETY PRECAUTIONS This device is to be serviced only by properly qualified service personnel. Consult the service manual for proper service procedures to assure continued safety operation and for precautions to be taken to avoid possible exposure to excessive microwave energy. PRECAUTIONS TO BE OBSERVED BEFORE AND DURING SERVICING TO AVOID POSSIBLE EXPOSURE TO EXCESSIVE MICROWAVE ENERGY...

  • Page 3: Table Of Contents

    CONTENTS (Page) SAFETY PRECAUTIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Inside front cover SPECIFICATIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1-1 CAUTIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2-1 INSTALLATIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3-1...

  • Page 4: Specifications

    SPECIFICATIONS ITEM DESCRIPTION Model LRM1250W Power Requirement 120 Volts AC 60 Hz 1500 Watts (13.8 A) Single phase, 3 wire grounded Power Output 1200 Watts full microwave power (IEC60705) Microwave Frequency 2450 MHz Magnetron 2M246 - 050GF Timer 0 ~ 9 min. 99 sec.

  • 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: Installations

    INSTALLATIONS BEFORE YOU BEGIN, READ THE FOLLOWING INSTRUCTIONS COMPLETELY AND CAREFULLY. INSTALLING GROUNDING INSTRUCTIONS For personal safety,this appliance must be fully 1. Empty the microwave oven and clean inside it with grounded at all times. a soft, damp cloth. Check for damage such as misaligned door, damage around the door or dents In the event of an electrical short circuit, grounding inside the cavity or on the exterior.

  • Page 7: Operating Instructions

    OPERATING INSTRUCTIONS FEATURES Oven Front Plate Window Door Screen Door Seal Display Window Control Panel Door Open Button Safety Door Lock System Turntable Roller Rest 1. DISPLAY: The display includes a clock and indicators that tell CONTROL PANEL you the time of day, cook time settings, and cooking functions selected.

  • Page 8: Operating Sequence

    OPERATING SEQUENCE The following is a description of component functions 7. CHILD LOCK during oven operation. This oven has a CHILD LOCK feature TO SET CHILD LOCK 1. CANCEL FUNCTION STOP/CLEAR • Touch Touch the pad whenever you need to STOP/CLEAR •...
  • Page 9 14. MELT STOP/CLEAR MELT NUMBER OF TABLE NOTE:Then the oven will start automatically. 15. SOFTEN STOP/CLEAR SOFTEN NUMBER OF TABLE NOTE:Then the oven will start automatically. 16. AUTO COOK STOP/CLEAR AUTO COOK NUMBER OF TABLE NOTE:Then the oven will start automatically. 17.CUSTOM SET CUSTOM STOP/CLEAR...

  • Page 10: Schematic Diagram

    SCHEMATIC DIAGRAM...

  • Page 11: Circuit Description

    CIRCUIT DESCRIPTION GENERAL DETAILS • A high voltage of approximately 2100 volts AC is • The low voltage transformer supplies the necessary generated in the secondary of the high voltage voltage to the micom controller when power cord is transformer which is increased by the action of the high plugged in.

  • Page 12: Service Information

    SERVICE INFORMATION TOOLS AND MEASURING INSTRUMENTS NECESSARY TOOLS NECESSARY MEASURING INSTRUMENTS Tools normally used for TV servicing are sufficient. • TESTER (VOLTS-DC, AC, Ohmmeter) Standard tools are listed below. • Microwave survey meter - Holaday HI-1500 • Diagonal pliers HI-1501 •...
  • Page 13 MEASUREMENT WITH OUTER CASE NOTES WHEN MEASURING REMOVED • Do not exceed meter full scale deflection. • The test probe must be removed no faster than • When you replace the magnetron, measure for 1 inch/sec (2.5 cm/sec) along the shaded area, microwave energy leakage before the outer case is otherwise a false reading may result.

  • Page 14: Measurement Of Microwave Power Output

    MEASUREMENT OF MICROWAVE POWER OUTPUT • Microwave power output measurement is made with • The microwave power output P in watts is calculated the microwave oven supplied at its rated voltage and from the following formula : operated at its maximum microwave power setting with a load of (1000±5) g of potable water.
  • Page 15 D. PCB ASSEMBLY REMOVAL Remove choke cover 1) Remove the control panel assembly from the cavity. (Refer to control panel assembly removal on previous page.) 2) Remove screws which hold the PCB SUB ASS’Y to the control panel. 3) Disconnect the flat cable from the PCB SUB ASS’Y and take off the PCB SUB ASS’Y Control Panel PCB Sub Asm...
  • Page 16 F. AIR DUCT ASSEMBLY REMOVAL H. REMOVING THE TURNTABLE MOTOR 1) Remove the turntable and rotating ring. 1) Disconnect the leadwire from lamp. 2) Lay the unit down on its back. 2) Remove the mounting screw to the magnetron. 3) Remove the turntable motor cover. The turntable base cover is easily removed by G.
  • Page 17 I. HIGH VOLTAGE TRANSFORMER L. INTERLOCK SYSTEM REMOVAL 1) INTERLOCK MECHANISM The door lock mechanism is a device which has 1) Discharge the high voltage capacitor. been specially designed to eliminate completely 2) Disconnect the leadwire from magnetron, high voltage microwave activity when the door is opened during transformer, and capacitor.

  • Page 18: Interlock Continuity Test

    INTERLOCK CONTINUITY TEST WARNING : FOR CONTINUED PROTECTION AGAINST EXCESSIVE RADIATION EMISSION, REPLACE ONLY WITH IDENTICAL REPLACEMENT PARTS. TYPE NO.SZM-V 16-FA-63 OR VP-533A-OF OR V-5230Q FOR PRIMARY SWITCH TYPE NO.SZM-V 16-FA-62 OR VP-532A-OF OR V-5220Q FOR MONITOR SWITCH TYPE NO.SZM-V 16-FA-63 OR VP-533A-OF OR V-5230Q FOR SECONDARY SWITCH A.

  • Page 19: Component Test Procedure

    COMPONENT TEST PROCEDURE 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 WIRE LEADS FROM THE PRIMARY WINDING OF THE HIGH VOLTAGE TRANSFORMER.
  • Page 20 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. HIGH VOLTAGE Measure the resistance. Normal: Momentarily indicates CAPACITOR (Ohm-meter scale: Rx1000) several ohms, and...
  • Page 21 COMPONENTS TEST PROCEDURE RESULTS RELAY 2 Check for continuity of relay 2 with an POWER ohm-meter. LEVEL (Remove wire leads from relay 2 and operate the unit.) 4 sec 18 sec 6 sec 16 sec 8 sec 14 sec 10 sec 12 sec 12 sec 10 sec...

  • Page 22: Trouble Shooting

    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. Check grounding before checking for trouble. 2.
  • Page 23 (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 24 (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 Replace fuse, Check continuity 1. Fuse blows. Continuity. monitor switch. primary, monitor, of monitor secondary switch (with...
  • Page 25 (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. of secondary does not count switch (with...
  • Page 26 (TROUBLE 5) No microwave oscillation even though oven lamp and fan motor run. (Display operates properly) CONDITION CHECK RESULT CAUSE REMEDY No microwave Defective PCB Replace PCB Disconnect the No continuity. oscillation. assembly assembly wire leads from relay 2 and check continuity Continuity.

  • Page 27: Exploded View

    #EV# EXPLODED VIEW INTRODUCTION OUTER CASE INTERIOR DOOR BASE PLATE LATCH BOARD CONTROL PANEL...
  • Page 28 #EV# DOOR PARTS 15006A 13581A 13552A 13536A 13213A 14890A 143501 13720D 14026A 14970A...
  • Page 29 #EV# CONTROLLER PARTS 24781M 23572A 268711 23506A WTP018 24510L 24970A 250201...
  • Page 30 #EV# OVEN CAVITY PARTS WSZ185 948502 33112U 33052A WTT010 33390G 36549S 35889A WTP013...
  • Page 31 #EV# LATCH BOARD PARTS WSZ085 466001 43500A 466003 466001...
  • Page 32 #EV# INTERIOR PARTS WSZ002 568771 56411A 50FZZA 948503 55006F 56930V 56549F 34930W WSZ085 54974S WEB001 55900A WTT 037 WSZ 002 WTT 028 50 CZZH 54810C 35012A WSZ 002 56912B WTT 028 56324A 56851D 948501 55262A WSZ 002 WEB001...
  • Page 33 #EV# BASE PLATE PARTS 56170D 63302A 63303A 65006B WSZ002 WTT021...

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