Goldstar Gms-7020mw Service Manual

MICROWAVE OVEN

SERVICE MANUAL

MODEL: GMS-7020MW

CAUTION

website: http://www.lgservice.com e-mail: http://www.lgeservice.com/techsup.html

BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.

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

A) Do not operate or allow the oven to be operated with the door open. B) Make the following safety checks on all ovens to be serviced before activating the magnetron or other

microwave source, and make repairs as necessary; (1) interlock operation, (2) proper door closing, (3) seal and sealing surfaces (arcing, wear, and other damage), (4) damage to or loosening of hinges and latches, (5) evidence of dropping or abuse.

C) Before turning on microwave power for any service test or inspection within the microwave generating

compartments, check the magnetron, wave guide or transmission line, and cavity for proper alignment, integrity, and connections.

D) Any defective or misadjusted components in the interlock, monitor, door seal, and microwave generation

and transmission systems shall be repaired, replaced, or adjusted by procedures described in this manual before the oven is released to the owner.

E) A microwave leakage check to verify compliance with the Federal Performance Standard should be

performed on each oven prior to release to the owner.

SAFETY PRECAUTIONS

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SAFETY PRECAUTIONS

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Inside front cover

SPECIFICATIONS

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1-1

CAUTIONS

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2-1

INSTALLATIONS

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3-1

OPERATING INSTRUCTIONS

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4-1

FEATURES

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4-1

CONTROL PANEL

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4-1

OPERATING SEQUENCE

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4-2

SCHEMATIC DIAGRAM

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4-3

CIRCUIT DESCRIPTION

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4-4

SERVICE INFORMATION

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5-1

TOOLS AND MEASURING INSTRUMENTS

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5-1

MICROWAVE LEAKAGE TEST

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5-1

MEASUREMENT OF MICROWAVE POWER OUTPUT

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5-3

DISASSEMBLY AND ADJUSTMENT

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5-3

INTERLOCK CONTINUITY TEST

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5-7

COMPONENT TEST PROCEDURE

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5-8

TROUBLE SHOOTING

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5-11

EXPLODED VIEW

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6-1

REPLACEMENT PARTS LIST

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7-1

CONTENTS

1-1

It is not recommended for commercial purposes.

ITEM

MODEL

Power Requirement

Power Output Microwave Frequency Magnetron Timer Outside Dimensions Cavity Dimensions Net Weight Shipping weight Control Complement

Accessories

DESCRIPTION

GMS-7020MW

120 Volts AC 60 Hz 900 Watts (8.0 A) Single phase, 3-wire grounded 600 Watts full microwave power (IEC60705) 2,450 MHz 2M213 0 ~ 35 min. 17

/16

” (W) x 11

/16

” (H) x 12

/16

” (D)

/16” (W) x 715/16” (H) x 119/16” (D)

24.7 lbs (approx.)

26.9 lbs (approx.) Mechanical Rotary System Power Control Cooking

Owner's manual Glass turntable Rotating ring

SPECIFICATIONS

• DO NOT operate on a 2-wire extension cord during repair and use.

• NEVER TOUCH any oven components or wiring during operation.

• BEFORE TOUCHING any parts of the oven, always remove the power plug from the outlet.

• For about 30 seconds after the oven stops, an electric charge remains in the high voltage capacitor. When replacing or checking, you must discharge the high voltage capacitor by shorting across the two terminals with an insulated screwdriver.

•

Remove your watches whenever working close to or

replacing the Magnetron.

• DO NOT touch any parts of the control panel circuit. A resulting static electric discharge may damage this P.C.B.

• NEVER operate the oven with no load.

• NEVER injure the door seal and front plate of the oven cavity.

• NEVER put iron tools on the magnetron.

• NEVER put anything into the latch hole and the interlock switches area.

• Proper operation of the microwave oven requires that the magnetron be assembled to the waveguide and cavity. Never operate the magnetron unless it is properly installed.

• Be sure that the magnetron gasket is properly installed around the dome of the tube whenever installing the magnetron.

2-1

CAUTIONS

Unlike other appliances, the microwave oven is high-voltage and high-current equipment. Though it is free from danger in ordinary use, extreme care should be taken during repair.

THE OVEN IS TO BE SERVICED ONLY BY PROPERLY QUALIFIED SERVICE PERSONNEL.

MICROWAVE RADIATION

Personnel should not be exposed to the microwave energy which may radiate from the magnetron or other microwave generating device if it is improperly used or connection. All input and output microwave connections, waveguide, flange, and gasket must be secure never operate the device without a microwave energy absorbing load attached. Never look into an open waveguide or antenna while the device is energized.

Gasket

ANTENNA

COOLING FIN

MAGNETRON CHASSIS GROUND

FILAMENT TERMINALS

MAGNETRON

INSTALLATIONS

3-1

INSTALLING

1. Empty the microwave oven and clean inside it with a soft, damp cloth. Check for damage such as misaligned door, damage around the door or dents inside the cavity or on the exterior.

2. Put the oven on a counter, table, or shelf that is strong enough to hold the oven and the food and utensils you put in it. (The control panel side of the oven is the heavy side. Use care when handling.)

3. Do not block the vent and the air intake openings. Blocking vent or air intake openings can cause damage to the oven and poor cooking results. Make sure the microwave oven legs are in place to ensure proper air flow.

4. The oven should not be installed in any area where heat and steam are generated, because they may damage the electronic or mechanical parts of the unit. Do not install the oven next to a conventional surface unit or above a conventional wall oven.

5. Use microwave oven in an ambient temperature less than 104°F(40°C).

6. Place the microwave oven on a sturdy and flat surface at least 10 cm(4 inches) from the wall.

7. Place the microwave oven as far away as possible from TV, RADIO, COMPUTER, etc., to prevent interference.

GROUNDING INSTRUCTIONS

For personal safety, this appliance must be fully grounded at all times.

In the event of an electrical short circuit, grounding reduces the risk of electrical shock. The plug must be plugged into an outlet that is properly installed and grounded.

BEFORE YOU BEGIN, READ THE FOLLOWING INSTRUCTIONS COMPLETELY AND CAREFULLY.

WARNING

Improper use of the grounding plug can result in a risk of electric shock. Do not, under any circumstances, cut or remove the third ground prong from the power cord plug.

PREFERRED METHOD

INSURE PROPER GROUND

EXISTS BEFORE USE

10cm

TEMPORARY METHOD

(ADAPTER PLUGS ARE NOT

PERMITTED IN CANADA)

ALIGN LARGE PRONGS/SLOTS

INSURE PROPER GROUND AND

FIRM CONNECTION BEFORE USE

4-1

OPERATING INSTRUCTIONS

FEATURES

Timer Knob

Power Knob

Oven Front Plate

Window Door Screen

Door Seal

Safety Door Lock System Turntable

Rotating Ring

The microwave oven is designed to be simple and easy to operate. Please follow these instructions carefully.

1. Place the food in a suitable cooking utensil. Open the microwave oven door and place the utensil in the center of the oven on the glass tray.

2. Close the oven door.

3. Turn the TIMER KNOB clockwise to set the cooking time.

4. When the TIMER reaches OFF, the signal sounds and the oven will automatically shut off.

5. Open the door and remove the food from the oven.

6. To stop cooking before the timer reaches OFF, either open the door or simply turn the timer to OFF.

NOTE :

1. The oven starts as soon as the KNOB is turned. We recommend turning the KNOB past the time you want and then turn back to the desired setting.

2. The door can be opened during the cooking process by pushing the Door Open Button. The timer will stop and the microwave activity will cease. When the door is closed, cooking will resume until the full cooking time has elapsed. After cooking is finished, the Timer will be at OFF.

After unpacking this appliance, examine the new oven for evidence of shipping damage. This is most important since a damaged oven may allow the escape of microwave energy. Make sure you remove all packing from the microwave cavity. Check the oven operation when unpacking the unit and any time the oven is not working properly.

1. Plug the power cord into an earthed electrical socket.

2. Place the glass tray inside the oven cavity.

3. Place a cup of water (at room temperature) inside the oven, on the glass tray.

4. Close the door securely.

5. Set the Timer for 3 to 4 minutes (note : microwave activity starts).

6. When the cooking time has elapsed, the signal will sound (note: all microwave activity stops).

7. If the oven is operating normally, the water will be hot.

OPERATION CHECK

OPERATING PROCEDURE

SCHEMATIC DIAGRAM

4-2

** NOTE : DOOR IS OPENED.

BK : BLACK BL : BLUE BN : BROWN

RD : RED WH : WHITE GN: GREEN

OVEN

THERMOSTAT

SECONDARY

SWITCH

MONITOR

SWITCH

OVEN

LAMP

FAN

MOTOR

TURN

TABLE

MOTOR

TIMER

MOTOR

BK BK

RDRD

T.MF.M T.T.MO.L

H.V DIODE

MAGNETRON

CHOKE FILTER(optional)

FUSE

15A

PRIMARY

SWITCH

TIMER

SWITCH

H.V

TRANSFORMER

H.V

CAPACITOR

AC 120V

60Hz

IMPORTANT SAFETY NOTE: THE COMPONENTS IN SHADED AREAS ON THIS SCHEMATIC DIAGRAM INCORPORATE SPECIAL FEATURES

IMPORTANT FOR PROTECTION FROM MICROWAVE RADIATION, FIRE, ELECTRICAL SHOCK, AND OTHER

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 A BASIC SCHEMATIC DIAGRAM, THE VALUES OF COMPONENTS AND

SOME PARTIAL CONNECTIONS ARE SUBJECT TO CHANGE FOR IMPROVEMENT.

4-3

CIRCUIT DESCRIPTION

GENERAL DETAILS

• When the door is closed, the primary switch is ON, the secondary switch is ON, and the monitor switch opens (contact COM and NO).

• The latches are secured by the latch board, the oven light turns on while the oven is operation.

WHEN THE TIMER KNOB IS ROTATED

• When the timer knob is rotated, the contacts of timer switch close.

• The contact of the secondary switch close the circuit.

• Power input is supplied to the high voltage transformer through the fuse to the primary timer and secondary switches.

• Turntable rotates

• The fan motor rotates and cools the magnetron by blowing air (coming from the intake on the baseplate).

• The air is also directed into the oven to exhaust the vapor in the oven through the upper plate.

• Cooking time starts counting down.

• 3.2 volts AC is generated from the filament winding of the high voltage transformer. This 3.2 volts is applied to the magnetron to heat the magnetron filament through two noise-preventing choke coils.

• A high voltage of approximately 2100 volts AC is generated in the secondary of the high voltage transformer which is increased by the action of the high voltage diode and charging of the high voltage capacitor.

• The negative 4,000 Volts DC is applied to the filament of the magnetron.

WHEN THE DOOR IS OPENED DURING COOKING

• Both the primary and timer switches are cut off primary winding voltage of the high voltage transformer.

• When the door is opened, the secondary switch is opened and when the door is closed, the secondary switch is closed.

• The timer, turntable and fan motor stop.

• As the door is opened, if the contact of primary switch fail to open, the fuse opens due to the large current surge caused by the monitor switch activation, which, in turn, stops magnetron oscillation.

FUSE

P/S

P/S : Primary Switch T/S : Tiemr Switch S/S : Secondary Switch

T/S S/S

H.V.

TRANS-

FORMER

FUSE

P/S

T/S S/S

M/S

P/S : Primary Switch T/S : Tiemr Switch M/S : Monitor Switch S/S : Secondary Switch

H.V.

TRANS-

FORMER

5-1

CAUTIONS

• Be sure to check microwave leakage prior to servicing the oven if the oven is operative prior to servicing.

• The service personnel should inform the manufacturer, importer, or assembler of any certified oven unit found to have a microwave emission level in excess of 5 mW/cm2and should

repair any unit found to have excessive emission levels at no cost to the owner and should ascertain the cause of the excessive leakage. The service personnel should instruct the owner not to use the unit until the oven has been brought into compliance.

• If the oven operates with the door open, the service personnel should:

- Tell the user not to operate the oven.

- Contact the manufacturer and CDRH (Center for Devices and Radiological Health)

immediately.

NOTE: Address on CDRH

Office of Compliance(HFZ-312) Center for Devices and Radiological Healthe 1390, Piccard Drive, Rockville. MD 20850

• The service personnel should check all surface and vent openings for microwave leakage.

• Check for microwave leakage after every servicing. The power density of the microwave radiation leakage emitted by the microwave oven should not exceed 4 mW/cm2. Always start measuring of an unknown field to assure safety for operating personnel from radiation leakage.

MEASURING MICROWAVE ENERGY LEAKAGE

• Pour 275±15cc of 20±5°C (68±9°F) water in a beaker which is graduated to 600 cc, and place the beaker on the center of the turntable.

• Set the energy leakage monitor to 2,450 MHz and use it following the manufacturer's recommended test procedure to assure correct result.

• When measuring the leakage, always use the 2inch (5 cm) spacer supplied with the probe.

• Operate the oven at its maximum output.

• Measure the microwave radiation using and electromagnetic radiation monitor by holding the probe perpendicular to the surface being measured

Move probe along shaded area

Probe scanning speed Less than 2.5 cm/sec (1 in/sec)

SERVICE INFORMATION

TOOLS AND MEASURING INSTRUMENTS

MICROWAVE LEAKAGE TEST

NECESSARY TOOLS

Tools normally used for TV servicing are sufficient. Standard tools are listed below.

• Diagonal pliers

• Long nose pliers

• Phillips screwdriver

• Flat blade screwdriver

• Wrench (size 5mm)

• Nutdriver (size 5mm)

• Adjustable wrench

• Soldering iron

• Solder

• Vinyl insulation tape

• Polishing cloth

NECESSARY MEASURING INSTRUMENTS

• TESTER (VOLTS-DC, AC, Ohmmeter)

• Microwave survey meter

- Holaday HI-1500 HI-1501

- Narda 8100

8200

• Inch scale

• 600 cc non conductive material beaker (glass or plastic), inside diameter: approx. 8.5 cm (3

in.)

• Cylindrical and made of borosilicate glass vessel. max. thickness: 3 mm outside diameter: approx. 190mm height: approx. 90mm

• Glass thermometer: 100°C or 212°F (1 deg scale)

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