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LG MB-4042G Service Manual

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MICROWAVE OVEN
SERVICE MANUAL
MODEL: MB-4042G
CAUTION
BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
Website http://biz.lgservice.com

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Summary of Contents for LG MB-4042G

  • Page 1 Website http://biz.lgservice.com MICROWAVE OVEN SERVICE MANUAL MODEL: MB-4042G 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 MODEL MB-4042G Power Requirement 230 Volts AC 50 Hz Single phase, 3 wire grounded Microwave 1,100W Grill 1,000W Combi 2,050W Power Output 700 Watts full microwave power (IEC60705) Microwave Frequency 2,450 MHz Magnetron 2M214 - 240GP Timer 60 Min.

  • 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 Oven Front Plate Window Door Screen Door Seal Display Window Control Panel Safety Door Lock System Turntable Grill Rack Roller rest CONTROL PANEL 1. AUTO WEIGHT DEFROST: Used to select the auto weight defrost. 2. AUTO COOK: Used to select the auto cook. 3.

  • Page 8: Operating Sequence

    OPERATING SEQUENCE 5. GRILL COOKING The following is a description of component functions during oven operation. Desired Stop/Clear Grill Start 1. SETTING THE CLOCK cooking time Set the Stop/Clear 6. COMBINATION COOKING clock correct time clock Desired NOTE: You can set 12 hour clock or 24 hour clock Desired Stop/Clear combi...

  • Page 9: Schematic Diagram

    SCHEMATIC DIAGRAM...

  • Page 10: Circuit Description

    CIRCUIT DESCRIPTION power of microwave oven as POWER LEVEL. GENERAL DETAILS (refer to page 1-1) • The low voltage transformer supplies the necessary • One complete cycle of relay 2 is 22 seconds. voltage to the micom controller when power cord is 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 4187 X (∆T) + 0.55 X (T ) X M with a load of (1000 ±...
  • Page 14 D. DOOR GROSS ASSEMBLY REMOVAL F. AIR DUCT ASSEMBLY REMOVAL 1) Open the door. 1) Disconnect the leadwire from lamp and MGT 2) Remove the choke cover very carefully with a flat- thermostat. blade screwdriver. 2) Remove the mounting screw to the magnetron. CAUTION : Be careful not to damage door seal plate by screwdriver.
  • Page 15 H. FAN MOTOR ASSEMBLY REMOVAL J. THE TURNTABLE MOTOR REMOVAL 1) Remove the turntable. 1) Discharge the high voltage capacitor. 2) Remove the turntable shaft VERY CAREFULLY 2) Disconnect the leadwire from fan motor, noise filter with a slotted screwdriver. and high voltage capacitor.
  • Page 16 K. PCB ASSEMBLY REMOVAL L. INTERLOCK SYSTEM 1) Remove the control panel assembly from the 1) INTERLOCK MECHANISM cavity. (Refer to control panel assembly removal The door lock mechanism is a device which has on previous page.) been specially designed to eliminate completely 2) Remove screws which hold the PCB SUB ASS’Y to microwave activity when the door is opened during 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 then...
  • Page 20 COMPONENTS TEST PROCEDURE RESULTS FUSE Check for continuity of the fuse with an Normal Abnormal multi-meter. NOTE: If the fuse is blown, check the primary, the secondary, and the monitor switches, H.V.D. and H.V.C. before replacing the fuse. If the fuse is blown by improper switch operation replace the defective switch and the fuse at the same time.
  • Page 21 COMPONENTS TEST PROCEDURE RESULTS Disconnect the 8 pin Check for P.C.B. connector. Cooking Start connector from P.C.B. (Refer to schemetic diagram) Cooking Start RELAY 2, RELAY 3 Relay 3 OF P.C.B. (Wire leads removed.) Note: Relay Relay 2: Microwave Relay 3: Grill Relay 2 Normal: Approx.

  • 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 Replace primary Malfunction of the Check continuity 1. Fuse blows. Continuity. and monitor monitor switch. of monitor switches.
  • 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 does No continuity. secondary switch. secondary switch.
  • 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 Disconnect the Defective P.C.B Replace P.C.B No continuity. oscillation. wire leads from assembly assembly relay 2 and check continuity Continuity.
  • Page 27 (TROUBLE 6) Oven does not cook properly when programmed for the set power level (Operates properly on HIGH) CONDITION CHECK RESULT CAUSE REMEDY Output is full when Defective P.C.B. Replace P.C.B. Disconnect the Abnormal. you set lower assembly. assembly. wire leads from power level.

  • Page 28: Exploded View

    EXPLODED VIEW INTRODUCTION OVEN CAVITY PARTS INTERIOR PARTS DOOR PARTS BASE PLATE PARTS LATCH BOARD PARTS CONTROL PANEL PARTS...
  • Page 29 DOOR PARTS 13581A 13552A 13536A 13213A 14890A 13720D 14026A 14970A...
  • Page 30 CONTROL PANEL PARTS 24781M 268711 23572A WTT028 23506A...
  • Page 31 OVEN CAVITY PARTS WTT021 35264A 33112U WTT021 948502 33550H WNZ015 33052M WTT010 35300S 35026G 33390G WSZ184 35889A 36549S WTP013...
  • Page 32 LATCH BOARD PARTS WSZ085 466001 466003 466001 43500A 44510A...
  • Page 33 INTERIOR PARTS WTT021 33808A 56411A WSZ062 56930V WSZ002 34930W WSZ002 50FZZA 56324A 56201A WSZ002 WTT037 56549F 55900A 54974S 56851D WSZ002 50CZZH 56912B WTT028 54810C 568771 55262A 948501...
  • Page 34 BASE PLATE PARTS 56170D 63302A 63303A 65006B WSZ002 WTT021...

  • Page 35: Replacement Parts List

    REPLACEMENT PARTS LIST FOR MODEL : MB-4042G LOC. PART NO. DESCRIPTION ALTER 3828W5A3529 MANUAL,OWNERS 3828W5S3284 MANUAL,SERVICE 3890W3W369B BOX,WHITE 13213A 3213W1A045C DOOR FRAME ASSEMBLY 13536A 3536W3A011Z SEAL TAPE 13552A 3552W1A058A CHOKE COVER 13581A 3581W0A041D DOOR ASSEMBLY 13720D 3720W0D256E PANEL,DOOR 14026A 4026W2A024A...
  • Page 36 LOC. PART NO. DESCRIPTION ALTER WSZ002 1SBF0402418 SCREW TAP TITE(S),BINDING HEAD WSZ062 4000W4A003A SCREW,DRAWING WSZ085 4B70188C SCREW,DRAWING WSZ184 1SZZW2Z001E SCREW,DRAWING WTP013 1TPL0402418 SCREW TAPPING,PAN HEAD WTT010 1TTG0402422 SCREW TAPPING,TRUSS HEAD WTT021 1TTL0402418 SCREW TAPPING,TRUSS HEAD WTT028 1TTL0402818 SCREW TAPPING,TRUSS HEAD WTT037 1TTL0403818 SCREW TAPPING,TRUSS HEAD...

  • Page 37: Schematic Diagram Of P.c.b

    SCHEMATIC DIAGRAM OF P.C.B...

  • Page 38: Printed Circuit Board

    PRINTED CIRCUIT BOARD...

  • Page 39: P.c.b Parts List

    P.C.B PARTS LIST LOC. PART NO DESCRPTION SPECIFICATION ALTER 6908W3YA01B BUZZER TFM-57 CW NINGBO EAST PIEZO 2048HZ 70DB 0CE2276H638 CAPACITOR,FIXED ELECTROLYTIC 220UF SMS,SG 25V 20% FM5 TP 5 0CE4776H618 CAPACITOR,FIXED ELECTROLYTIC 470UF SMS,SG 25V 20% FL TP 5 0CE1076H638 CAPACITOR,FIXED ELECTROLYTIC 100UF SMS,SG 25V 20% FM5 TP 5 0CE1076D638 CAPACITOR,FIXED ELECTROLYTIC...
  • Page 40 RESISTOR,FIXED CARBON FILM 4.7K OHM 1/6 W 5% TA26 6920W2D010A RELAY OJ-SS-112LM OEG 250VAC 3A 12VDC 1A 6920W5A012A RELAY G5G-1A-DT1-LG OMRON 250VAC 16A 12VDC 1A 6920W5A012A RELAY G5G-1A-DT1-LG OMRON 250VAC 16A 12VDC 1A 0IZZW5A213B IC,DRAWING TMP87CH47U 44QFP TRAY MB-3883A EUROPE...
  • Page 41 June, 2003 P/NO : 3828W5S3284 Printed in Korea...

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