LG MS-256NB Service Manual
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LG MS-256NB Service Manual

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MICROWAVE OVEN
SERVICE MANUAL
MODEL: MS-256NB / 256NR
CAUTION
BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.

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Summary of Contents for LG MS-256NB

  • Page 1 MICROWAVE OVEN SERVICE MANUAL MODEL: MS-256NB / 256NR CAUTION BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.

  • 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 MS-256NB / 256NR MODEL 230 Volts AC 50 Hz Power Requirement 1,250 Watts Single phase, 3 wire grounded 900 Watts full microwave power (IEC705) Power Output 2,450 MHz Microwave Frequency 2M214 - 39F, 2M218J Magnetron 10 sec. ~ 99 min. 50 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 EARTHING INSTRUCTIONS 1. Empty the microwave oven and clean inside it with This microwave oven is designed to be used in a fully a soft, damp cloth. Check for damage such as earthed condition.

  • Page 7: Operating Instructions

    OPERATING INSTRUCTIONS FEATURES Window Door Screen Door Seal Control Panel Safety Door Lock System Turntable Rotating Ring CONTROL PANEL 1. INDICATORS 2. AUTO WEIGHT COOK: Used to cook the foods listed by one touch. 3. DEFROST: Used to select the desired auto weight defrost programmed with weight.

  • Page 8: Operating Sequence

    OPERATING SEQUENCE The following is a description of component functions 5. MULTI-STAGE MICROWAVE during oven operation. COOKING 1ST STAGE 1. SETTING THE CLOCK STOP/CLEAR POWER TIME START STOP/CLEAR CLOCK NUMBER CLOCK 2ND STAGE NOTE: 1) This is a 24 hour clock. 2) Clock will operate as long as power is POWER TIME...

  • Page 9: Schematic Diagram

    SCHEMATIC DIAGRAM...

  • Page 10: Circuit Description

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

  • Page 11: 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 • Diagonal pliers - Holaday HI-1500 • Long nose pliers HI-1501 •...
  • Page 12 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 13: 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 4187 x (∆T) a load of (1000±5) g of potable water.
  • Page 14 D. DOOR GROSS ASSEMBLY REMOVAL F. FAN MOTOR ASSEMBLY REMOVAL 1) Open the door. 1) Discharge the high voltage capacitor. 2) Remove the choke cover very carefully with a flat- 2) Disconnect the leadwire from fan motor, fuse board blade screwdriver. and high voltage capacitor.
  • Page 15 H. AIR DUCT ASSEMBLY REMOVAL J. REMOVING THE TURNTABLE MOTOR 1) Remove the turntable. 1) Disconnect the leadwire from the lamp. 2) Remove the turntable shaft VERY CAREFULLY 2) Remove the mounting screw to the magnetron. with a slotted screwdriver. 3) Lay the unit down on its back.
  • Page 16 K. PCB ASSEMBLY REMOVAL 2) MOUNTING OF THE PRIMARY/MONITOR/ SECONDARY SWITCHES TO THE LATCH 1) Remove the control panel assembly from the BOARD cavity. (Refer to control panel assembly removal on previous page.) 2) Remove screws which hold the PCB SUB ASS’Y to the control panel.

  • Page 17: 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 FOR PRIMARY SWITCH TYPE NO. SZM-V 16-FA-62 OR VP-532A-OF FOR MONITOR SWITCH TYPE NO. SZM-V 16-FA-63 OR VP-533A-OF FOR SECONDARY SWITCH B.

  • Page 18: 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 19 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 20 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.) 6 sec 16 sec 10 sec 12 sec Relay 1 14 sec 8 sec Relay 2 18 sec 4 sec...

  • Page 21: 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 22 (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 23 (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 switches, and switch (with...
  • Page 24 (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 25 (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 26 (TROUBLE 5) No microwave oscillation even though oven lamp and fan motor run. (Display operates properly) CONDITION CHECK RESULT CAUSE REMEDY Defective PCB Replace PCB Output is full power Disconnect the Abnormal. assembly. assembly. when you set lower wire leads from power level.

  • Page 27: Exploded View

    EXPLODED VIEW INTRODUCTION OVEN CAVITY PARTS INTERIOR PARTS BASE PLATE PARTS DOOR PARTS LATCH BOARD PARTS CONTROL PANEL PARTS...
  • Page 28 DOOR PARTS 13581A 15006A 13536A 13552A 13213A 14890A 13720D 14026A 14970A 13806F...
  • Page 29 CONTROL PANEL PARTS 24781S 268712 268711 250201 23572A 250203 53551S 250202 250204 250205...
  • Page 30 OVEN CAVITY PARTS 33112U WTT021 WTT010 WSZ092 33052M 33390G 34960A 34370T 36549S 35889A WTP013...
  • Page 31 LATCH BOARD PARTS 435001 WSZ085 466001 466003 435011 466002 44510A...
  • Page 32 INTERIOR PARTS 568771 WSZ062 WSZ062 50FZZA 56411A 56201A 56930M WSZ085 56549F 54974S WSZ002 559001 WTT037 50CZZH 56851D 56912B WSZ002 WSZ002 968101 56851C 55262A 948501 WTT028 54810C 56324A WSZ002 56201B...
  • Page 33 BASE PLATE PARTS 56170D 633021 633031 WTT021 647781 WTT030 WSZ002 WSZ062...

  • Page 34: Schematic Diagram Of P.c.b

    SCHEMATIC DIAGRAM OF P.C.B...

  • Page 35: Printed Circuit Board

    PRINTED CIRCUIT BOARD...

This manual is also suitable for:

Ms-256nr

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