LG MC-7684B Service Manual
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LG MC-7684B Service Manual

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삼
흥
정
판
MICROWAVE OVEN
SERVICE MANUAL
MODEL: MC-7684B
CAUTION
BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
P/NO : MFL37307701
MC-7684BS
Website: http://biz.lgservice.com
November, 2006
Printed in Korea

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  • Page 1 삼 흥 정 판 Website: http://biz.lgservice.com MICROWAVE OVEN SERVICE MANUAL MODEL: MC-7684B MC-7684BS CAUTION BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL. November, 2006 P/NO : MFL37307701 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 MC-7684B / MC-7684BS Power Requirement 230 Volts AC 50 Hz Single phase, 3 wire grounded Microwave 1300W Grill 1150W Combination 2650W Convection 1350W (Max. 2450W) Power Output 900 Watts full microwave power (IEC60705) Microwave Frequency 2450 MHz...

  • 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 Control Panel Safety Door Lock System Turntable Rotating Ring Metal Tray High Rack Low Rack CONTROL PANEL 1. KNOB: Used to select the cooking mode. 2. AUTO COOK: Used to select the auto cook. 3.

  • Page 8: Operating Sequence

    OPERATING SEQUENCE The following is a description of component functions 7. AUTO COOK during oven operation. Auto Weight Stop Start/Quick Start Cook (kg) 1. SETTING THE CLOCK 8. SPECIAL COOK Stop Clock Set the hour Clock Special Weight Stop Start/Quick Start Cook (kg) Set the...

  • Page 9: Schematic Diagram

    SCHEMATIC DIAGRAM...

  • Page 10: Circuit Description

    CIRCUIT DESCRIPTION GENERAL DETAILS WHEN THE DOOR IS OPENED DURING COOKING • The low voltage transformer supplies the necessary voltage to the micom controller when power cord is • Both the primary switch and relay 2 are cut off primary 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...
  • Page 14 D. DOOR 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. REMOVING THE TURNTABLE MOTOR 1) Discharge the high voltage capacitor. 1) Remove the turntable. 2) Disconnect the leadwire from fan motor, noise filter 2) Remove the turntable shaft VERY CAREFULLY and high voltage capacitor. with a slotted screwdriver.
  • Page 16 K. C-MOTOR, THERMISTOR AND SHEATH HEATER REMOVAL 1) Remove the two screws securing the cover assembly to the oven cavity. 2) Disconnect the leadwire from the circulation motor terminal and the sheath heater. 3) Remove the screws of the thermistor, guide assy- chamber and lift up the guide assy-chamber.

  • 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 TYPE NO.

  • 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 OF P.C.B. Relay 3 (Wire leads removed.) Note: Relay Relay 1: Turntable motor Relay 1 Oven lamp Relay 2: Microwave...
  • Page 22 COMPONENTS TEST PROCEDURE RESULTS Normal : COM-230V : Approx. 150 Ω CIRCULATION MOTOR Measure the resistance. COM-24V : Approx. 20 Ω (Wire leads removed) (Multi-meter scale :R x 1) Abnormal : Infinite or several ohm. (BN) 230V(BL) NOTE: (YL) ) = WIRE COLOR Cooking Start RELAY 4, 6 OF P.C.B (Disconnect the 9 pin...

  • 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 Replace primary Malfunction of the Check continuity 1. Fuse blows. Continuity. and monitor monitor switch. of monitor switches.
  • 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 Replace Defective Check continuity 1.Setting time does 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 Disconnect the Defective P.C.B Replace P.C.B No continuity. assembly oscillation. wire leads from assembly relay 2 and check continuity Continuity.
  • Page 28 (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 29: Exploded View

    #EV# EXPLODED VIEW INTRODUCTION MODEL: MC-7684B MC-7684BS OVEN CAVITY PARTS INTERIOR PARTS DOOR PARTS BASE PLATE PARTS LATCH BOARD PARTS CONTROL PANEL PARTS...
  • Page 30 #EV# DOOR PARTS 13581A 15006A 13552A 13213A 14890A 13720D 14026A WTP018 14970A 13650A...
  • Page 31 #EV# CONTROL PANEL PARTS 24781S 268711 WTP004 23572A 25020T 25020G 24940P 25020E 23790D 25020K 25020S 24940D...
  • Page 32 #EV# OVEN CAVITY PARTS WNH001 44360A 34810M 33112U WSZ002 368771 35300A 34810H 33550H WSZ002 34810H WTT011 WTT010 33052M 33390G 33390M 35026G 34370T 34980A 35026C 35889A 36549S WTP013...
  • Page 33 #EV# LATCH BOARD PARTS WSZ085 43500A 466001 43501A 466001 466003 466001 44510A...
  • Page 34 #EV# INTERIOR PARTS WSZ185 WSZ062 568771 Button Head 56411A 33809A (Torx style 2) 535041 WSZ228 36549C 348102 55900N 348103 WTT021 54974A 56322A 55900C 54350S 54810S WWS005 WNH002 535042 55300S WSZ228 56208A 348101 WTT029 50FZZA WSZ002 568772 WTT021 56201A 54974S WTT037 WTP004 56549F WSZ002...
  • Page 35 #EV# BASE PLATE PARTS 56170D 63302A 63303A 647781 WSZ002 WTT030 WTT021...

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