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LG MB-339ME Service Manual

Microwave/grill oven
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MICROWAVE/GRILL OVEN
SERVICE MANUAL
MODEL : MB-339ME/MB
CAUTION
BEFORE SERVICING THE UNIT, READ
THE SAFETY PRECAUTIONS IN THIS MANUAL.

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Summary of Contents for LG MB-339ME

  • Page 1 MICROWAVE/GRILL OVEN SERVICE MANUAL MODEL : MB-339ME/MB 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 MB-339ME/MB MODEL 120 Volts AC 60 Hz Power Requirement MICROWAVE......1,300 Watts (12.0A) GRILL........1,000 Watts (8.5A) Single phase, 3 wire grounded 900 Watts full microwave power (IEC705) Power Output 2,450 MHz Microwave Frequency 2M214-39 Magnetron 0 ~ 99 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 1. Empty the microwave oven and clean inside it with For personal safety, this appliance must be fully a soft, damp cloth. Check for damage such as grounded at all times.

  • 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 Grill Rack Rotating Ring CONTROL PANEL 1. ONE TOUCH COOK: To select the desired auto cook setting 2.

  • Page 8: Operating Sequence

    OPERATING SEQUENCE 7. AUTO WEIGHT DEFROST COOKING The following is a description of component functions during oven operation. AUTO DESCONG NUMBER OF PARAR/BORRAR INICIO POR PESO WEIGHT 1. SETTING THE CLOCK 8. CHILD LOCK PARAR/BORRAR RELOJ NUMBER RELOJ This oven has a CHILD LOCK feature TO SET CHILD LOCK ex.) To set 4:30, touch number key [4],[3], and [0].
  • Page 9 IMPORTANT SAFETY NOTE: THE SHADED AREAS ON THIS SCHEMATIC DIAGRAM INCORPORATE SPECIAL FEATURES IMPORTANT FOR PROTECTION FROM MICROWAVE RADIATION, FIRE, ELECTRICAL SHOCK, AND HAZARDS. WHEN SERVICING IT IS ESSENTIAL THAT ONLY MANUFACTURER'S SPECIFIED PARTS BE USED FOR THE CRITICAL COMPONENTS IN THE SHADED AREAS OF THE SCHEMATIC DIAGRAM. NOTICE: SINCE THIS IS BASIC SCHEMATIC DIAGRAM, THE VALUES OF COMPONENTS AND SOME PARTIAL CONNECTIONS ARE SUBJECT TO CHANGE FOR IMPROVEMENT.

  • 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 transformer which is increased by the action of the high • The low voltage transformer supplies the necessary voltage diode and charging of the high voltage voltage to the micom controller when power cord is capacitor.

  • 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. PCB ASSEMBLY REMOVAL Remove choke cover cap 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 15 F. MAGNETRON REMOVAL G. SUCTION GUIDE MAIN ASSEMBLY 1) Disconnect the leadwire from the magnetron. NOTE: Suction Guide Main ASS’Y consists of Latch 2) Carefully remove the mounting screws holding the Board ASS’Y and Suction Guide ASS’Y. To repair any of magnetron and the waveguide.
  • Page 16 H. LATCH BOARD ASSEMBLY AND J. HIGH VOLTAGE TRANSFORMER REMOVAL SUCTION GUIDE ASSEMBLY NOTE: Suction Guide Main ASS’Y consists of Latch 1) Discharge the high voltage capacitor. Board ASS’Y and Suction Guide ASS’Y. To repair any of 2) Disconnect the leadwire from magnetron, high voltage them, the Suction Guide Main ASS’Y should be removed transformer, and capacitor.
  • Page 17 M. INTERLOCK SYSTEM K. HIGH VOLTAGE CAPACITOR AND DIODE 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 (refer to page 2-1) microwave activity when the door is opened during 2) Disconnect the leadwire from the high voltage cooking and thus to prevent the danger resulting 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 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 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 HEATER ELEMENT Measure the resistance. Normal: (Wire leads removed.) (Multi-meter scale:RX1) Gill heater Approx.55 Ω (at 20-30˚C) Normal: Measure the resistance with 500V-100M more than 0.5M Ω Ohm insulation resistance meter. NOTE: Make sure heater is fully cooled when tested. 0˚C~Approx 180˚C Approx 180˚C MAGNETRON THERMOSTAT...
  • Page 22 COMPONENTS TEST PROCEDURE RESULTS Check for continuity of relay 2 with an RELAY 2 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 23: 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 24 (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 25 (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 26 (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 27 (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 28 (TROUBLE 6) Grill CONDITION CHECK RESULT CAUSE REMEDY 1. Heater is not Malfunction the Heater Abnormal Replace operating heater. Normal Replace or Wire connection No continuity Open or loosen. connect tighty 2. Lower tempera- Malfunction the Heater Abnormal Replace ture in the oven. heater Normal Defective PCB...

  • Page 29: Exploded View

    EXPLODED VIEW INTRODUCTION OVEN CAVITY PARTS INTERIOR PARTS BASE PLATE PARTS DOOR PARTS SUCTION GUIDE MAIN PARTS CONTROL PANEL PARTS...
  • Page 30 DOOR PARTS 15006A 13552A 13536A 13213A 13581A 14026A 14970A 13720D 13352A...
  • Page 31 CONTROL PANEL PARTS WTP028 268771 23572A 26638A 24781M WTP018 24510L 24970A 250201...
  • Page 32 OVEN CAVITY PARTS WTT021 35264A 3112U WTT021 348102 35301A 33550H 948502 35300A WMT002 948504 348101 33052M 340511 WTT010 35026A 34960A 33390G 948503 36549S 35889A WTP013 368771...
  • Page 33 SUCTION GUIDE PARTS 50FZZA 55006F WTT028 568771 56912B 56930V 559001 435001 466002 54974S 466003 WTT037 56549F 435011 466001 WSZ084...
  • Page 34 INTERIOR PARTS WSZ002 WTP028 54826A 56411A WTP006 WTP004 56930G 968101 54810A 56324A WSZ002...
  • Page 35 BASE PLATE PARTS 50CZZH 34810C 56851D WSZ002 633022 56170D 633021 948501 647781 647781 W067 WTT028 W101 633032 633031...

  • Page 36: Schematic Diagram Of P.c.b

    SCHEMATIC DIAGRAM OF P.C.B.

  • Page 37: Printed Circuit Board

    PRINTED CIRCUIT BOARD...
  • Page 38 Jan., 2000 July, 1997 P/NO. 3828W5S1408 Printed in Korea P/NO. 3828W5S0450 Printed in Korea...

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