Goldstar Mab745w, Mab745w01, Mab745b01, Mab745b Service Manual

Website http://us.lgservice.com

MICROWAVE OVEN

SERVICE MANUAL

MODEL: MAB745W

CAUTION

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

P/NO : 3828W5S3839

MAB745B

May, 2004

Printed in Korea

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

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.

CAUTION

MICROWAVE RADIATION

DO NOT BECOME EXPOSED TO RADIATION FROM THE MICROWAVE GENERATOR OR OTHER PARTS CONDUCTING MICROWAVE ENERGY.

CONTENTS

(Page)

SAFETY PRECAUTIONS

SPECIFICATIONS

CAUTIONS

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INSTALLATIONS

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OPERATING INSTRUCTIONS

FEATURES

CONTROL PANEL

OPERATING SEQUENCE

SCHEMATIC DIAGRAM (I)

SCHEMATIC DIAGRAM (II)

CIRCUIT DESCRIPTION

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SERVICE INFORMATION

TOOLS AND MEASURING INSTRUMENTS

MICROWAVE LEAKAGE TEST

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Inside front cover

1-1

2-1

3-1

4-1

4-2

4-3

4-4

4-5

5-1

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5-1

MEASUREMENT OF MICROWAVE POWER OUTPUT

DISASSEMBLY AND ADJUSTMENT

INTERLOCK CONTINUITY TEST

COMPONENT TEST PROCEDURE

TROUBLE SHOOTING

EXPLODED VIEW

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REPLACEMENT PARTS LIST

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5-3

5-7

5-8

5-12

6-1

7-1

SPECIFICATIONS

Back side

ITEM

Model

Power Requirement

Power Output

Microwave Frequency

Magnetron

Timer

Outside Dimensions

Cavity Dimensions

Net Weight

Shipping weight

Control Complement

DESCRIPTION

MAB745W / MAB745B

120 Volts AC 60 Hz

950 Watts (9.0A)

Single phase, 3 wire grounded

700 Watts full microwave power (IEC60705)

2450 MHz

2M214-39F

0 ~ 9 min. 99 sec.

17 7/8” (W) x 103/16” (H) x 13” (D)

12 3/8” (W) x 7 15/16” (H) x 11 9/16” (D)

25.4 lbs (approx.)

27.6 lbs (approx.)

Touch Control System

Clock : 1:00 - 12:59

Microwave Power for Variable Cooking

Power level

HIGH --------------------------- Full power throughout the cooking time

9 (Saute)---------approx. 90% of Full power, 8 (Reheat)-------------approx. 80%

7 (Med.-High)---------------------approx. 70%, 6 (Medium)------------approx. 60%

5 (Med.-Low)---------------------approx. 50%, 4 (Defrost)-------------approx. 40%

3 (Low)-----------------------------approx. 30%, 2 (Simmer)------------approx. 20%

1 (Warm)---------------------------approx. 10%

Rating Label Location

Accessories

This microwave oven is designed for household use only.

Owner's manual & cooking guide

Glass turntable

Roller Rest

It is not recommended for commercial purposes.

1-1

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.

• 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 stop, 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.

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.

• 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.

ANTENNA

Gasket

• 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.

COOLING FIN

FILAMENT TERMINALS

MAGNETRON CHASSIS GROUND

MAGNETRON

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

2-1

INSTALLATIONS

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

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).

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.

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

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.

TEMPORARY METHOD

(ADAPTER PLUGS ARE NOT

PERMITTED IN CANADA) ALIGN

LARGE PRONGS/SLOTS

INSURE PROPER GROUND AND

FIRM CONNECTION BEFORE USE

3-1

OPERATING INSTRUCTIONS

Oven Front Plate

Window Door Screen

Door Seal

Display Window

Safety Door Lock System Turntable

Roller rest

Control Panel

FEATURES

CONTROL PANEL

1. INDICATORS

2. ONE TOUCH CONTROL: Used to cook the foods

listed by one touch.

3. AUTO DEFROST: Used to select the desired auto weight defrost programmed with weight pad.

4. NUMBER: Used to set for time of day, cooking time, power level or defrost weight.

5. STOP/CLEAR: Used to stop oven and clear all entries except time of day.

6. CLOCK: Used to set the time of day.

7. TIME: Used to cook food for a desired time.

8. POWER: Used to select power level for cooking.

9. Ez On: Allows you to cook for 30 seconds at 100%

power by simply touching this pad.

10. START: One tap allows over to begin functioning.

11. TIMER

12. Q DEFROST

4-1

OPERATING SEQUENCE

The following is a description of component functions during oven operation.

1. SETTING THE CLOCK

STOP/CLEAR

ex.) To set 4:30,touch number key [4 ],[3 ], and [0 ].

NOTE: 1) This is a 12 hour clock.

2) Clock will operate as long as power is applied to the oven.

CLOCK CLOCKNUMBER

2. CANCEL FUNCTION

Touch the pad whenever you need to

cancel an entry or a function currently in use.

The display will return either to the last item entered

or to the clock.

STOP/CLEAR

3. Ez On

6.MULTI-STAGE COOKING

1ST STAGE

STOP/CLEAR

2ND STAGE

1ST STAGE

TIME

NUMBER

TIME

NUMBER

START

7.AUTO DEFROST COOKING

POWER

STOP/CLEAR

Ez On

4. ONE TOUCH COOKING

STOP/CLEAR

NOTE: Heat only 1 package at a time

POPCORN

5.TIME COOKING

STOP/CLEAR

TIME POWERNUMBER

NUMBER START

STOP/CLEAR

AUTO

DEFROST

NUMBER OF

WEIGHT

8. CHILD LOCK

This oven has a CHILD LOCK feature

TO SET CHILD LOCK

• Touch the pad

• Touch and hold 0 pad L appear on

the display.

TO CANCEL CHILD LOCK

• Touch the pad

• Touch and hold 0 pad L disappear.

START

4-2

SCHEMATIC DIAGRAM (I)

*Check the Rating Model No.

4-3

SCHEMATIC DIAGRAM (II)

*Check the Rating Model No. (ADD Noise filter)

4-4

CIRCUIT DESCRIPTION

FUSE

H.V.

TRANS-

FORMER

RELAY 2

MICOM CONTROLLER

SECONDARY SWITCH

MONITOR

SWITCH

PRIMARY

SWITCH

GENERAL DETAILS

• The low voltage transformer supplies the necessary voltage to the micom controller when power cord is plugged in.

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

WHEN SELECTING COOKING POWER LEVEL AND TIME

•

The micom controller memorizes the function you set.

•

The time you set appears in the display window.

• Each indicator light turns on to indicate that the stage has been set.

WHEN TOUCHING THE START PAD

• The coil of the relay is energized by the micom controller.

• Power input is supplied to the high voltage transformer through the fuse to the primary switch and relay 2.

• Turntable rotates.

• 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 OVEN IS SET AT ANY LEVEL EXCEPT MAXIMUM.

• The micom controller controls the ON-OFF time of relay 2 by the applied signal to vary the average output power of microwave oven as POWER LEVEL.

(refer to page 1-1)

• One complete cycle of relay 2 is 22 seconds.

WHEN THE DOOR IS OPENED DURING COOKING

• Both the primary switch and relay 2 are cut off primary winding voltage of the high voltage transformer.

• ON-OFF of relay 2 is coupled electrically with opening and closing of the secondary switch.

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

• The cooking time stops counting down.

• Relay stops functioning.

• As the door is opened, if the contact of primary switch

and relay 2 and/or secondary switch fails to open, the fuse opens due to the large current surge caused by the monitor switch activation, which in turn stops magnetron oscillation.

• The fan motor rotates and cools the magnetron by blowing the 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.

4-5

FUSE

PRIMARY

SWITCH

MONITOR

SWITCH

RELAY 2

MICOM CONTROLLER

H.V.

TRANS-

FORMER

SECONDARY SWITCH

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