LG GoldStar GMS-7020UW Service Manual
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LG GoldStar GMS-7020UW Service Manual

LG GoldStar GMS-7020UW Service Manual

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Website: http://us.lgservice.com
MICROWAVE OVEN
SERVICE MANUAL
MODEL : GMS-7020UW
CAUTION
BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
July, 2002
P/NO : 3828W5S2322
Printed in Korea

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  • Page 1 Website: http://us.lgservice.com MICROWAVE OVEN SERVICE MANUAL MODEL : GMS-7020UW CAUTION BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL. July, 2002 P/NO : 3828W5S2322 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 GMS-7020UW MODEL 120 Volts AC 60 Hz Power Requirement 1,000 Watts (8.5 A) Single phase, 3 wire grounded 700 Watts full microwave power (IEC60705) Power Output 2,450 MHz Microwave Frequency 2M213 Magnetron 0 ~ 99 min. 99 sec. Timer ”...

  • 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 Safety Door Lock System Turntable Rotating Ring CONTROL PANEL 1. DISPLAY WINDOW 2. ONE TOUCH CONTROL: Touch this pad to select programming food items. 3. AUTO DEFROST: This feature provides you with the best defrosting method for frozen foods.

  • Page 8: Operating Sequence

    OPERATING SEQUENCE The following is a description of component functions during oven operation. 1. SETTING THE CLOCK 7. AUTO DEFROST COOKING AUTO NUMBER STOP/CLEAR CLOCK NUMBER CLOCK START/PAUSE START DEFROST OF WEIGHT ex.) To set 4:30, touch number key [4],[3], and [0]. 8.

  • 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 E. HIGH VOLTAGE TRANSFORMER 1) Open the door. REMOVAL 2) Remove the choke cover very carefully with a 1) Discharge the high voltage capacitor. flat-blade screwdriver. 2) Disconnect the leadwire from magnetron, high voltage CAUTION : Be careful not to damage door seal plate transformer, and capacitor.
  • Page 15 H. AIR DUCT ASSEMBLY REMOVAL J. REMOVING THE TURNTABLE MOTOR 1) Disconnect the leadwire from lamp. 1) Remove the turntable. 2) Remove the turntable shaft VERY CAREFULLY 2) Remove the mounting screw to Latch Board. with a slotted screwdriver. 3) Lay the unit down on its back. I.
  • 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 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.

  • 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 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 Relay 1 10 sec 12 sec 12 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 Replace fuse, Malfunction of the Check continuity 1. Fuse blows. Continuity. primary, monitor, monitor switch. of monitor secondary 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: Exploded View

    #EV# EXPLODED VIEW INTRODUCTION...
  • Page 27 #EV# DOOR PARTS 13552A 13581A 13213A 13536A 13352A 14026A 14970A 13720D...
  • Page 28 #EV# CONTROLLER PARTS 24781M 268711 23572A 23506A WTP028...
  • Page 29 #EV# OVEN CAVITY PARTS 35006U WTT021 33112U 34810A WTT010 33390G 33052A 35889A 36549S WTP013...
  • Page 30 #EV# LATCH BOARD PARTS 466001 466003 466001 43500A WSZ085 44510A...
  • Page 31 #EV# INTERIOR PARTS 56201B 56411A 56930V WSZ002 WSZ002 50FZZA 56324A 56201A WSZ002 WTT037 56549F 55900A 54974S 56912B 568771 55262A...
  • Page 32 #EV# BASE PLATE PARTS WTT028 56170D 54810C 63303A 50CZZH 56851D 63302A 65006B WTT021 WSZ002...

  • Page 33: Schematic Diagram Of P.c.b

    SCHEMATIC DIAGRAM OF P.C.B.

  • Page 34: Printed Circuit Board

    PRINTED CIRCUIT BOARD...

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