LG MS3846VRL Service Manual

MICROWAVE OVEN

SERVICE MANUAL

MODEL: MS3846VRL

CAUTION

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

Website http://biz.lgservice.com

P/NO : MFL31039026

January, 2011

Printed in Korea

삼 흥

정 판

Internal Use Only

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.

Only for training and service purposes

CONTENTS

(Page)

SAFETY PRECAUTIONS

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Inside front cover

SPECIFICATIONS

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1-1

CAUTIONS

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2-1

INSTALLATION

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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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4-4

CIRCUIT DESCRIPTION

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4-5

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

Only for training and service purposes

SPECIFICATIONS

1-1

This microwave oven is designed for household use only.

It is not recommended for commercial purposes.

DESCRIPTION

MS3846VRL

230/240 V~ 50 Hz 1600 watt Single phase, 3 wire grounded

1100 watt full microwave power (IEC60705)

2450 MHz

2M289-M47J1

0 ~ 99 min. 99 sec.

556mm (W) x 320mm (H) x 435mm (D)

398mm (W) x 265mm (H) x 402mm (D)

17.5 kg (approx.)

19.5 kg (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%

Owner's manual & cooking guide

Glass turntable

Rotating Ring

Keep Moisture

ITEM

MODEL

Power Requiremen

Power Output

Microwave Frequency

Magnetron

Timer

Outside Dimensions

Cavity Dimensions

Net Weight

Shipping weight

Control Complement

Rating Label

Location

Accessories

Only for training and service purposes

CAUTIONS

2-1

• 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.

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

Only for training and service purposes

INSTALLATION

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.

EARTHING INSTRUCTIONS

This microwave oven is designed to be used in a fully earthed condition. It is imperative, therefore, to make sure it is properly earthed before servicing

WARNINGTHIS APPLIANCE MUST BE EARTHED

IMPORTANT

As the colors of the wires in the mains lead of this appliance may not correspond with the colored markings identifying the terminals in your plug, proceed as follows.

The wire which is colored green-and-yellow must be connected to the terminal in the plug which is marked with the letter E or by the earth symbol ( ) or colored green or green-and-yellow.

The wire which is colored blue must be connected to the terminal in the plug which is marked with the letter N or colored black.

The wire which is colored brown must be connected to the terminal in the plug which is marked with the letter L or colored red.

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

10cm

The wires in this mains lead are colored in accordance with the following code:

Green-and-yellow: Earth Blue: Neutral Brown: Live

Only for training and service purposes

OPERATING INSTRUCTIONS

4-1

FEATURES

CONTROL PANEL

1. DISPLAY. The Display includes a clock and indicators

that tell you time of day, cooking time settings, and cooking functions selected.

2. ONE TOUCH AUTO MENU.

3. AUTO COOK: Used to select the auto cook.

4. BREAKFAST MENU.

5. CHICKEN CHOICES.

6. AUTO REHEAT: Used to select the auto reheat.

7. AUTO DEFROST: This feature provides you with the

best defrosting method for frozen foods.

8. QUICK DEFROST: You can thaw specific foods and

weight very quickly.

9. MELT.

10. SOFTEN.

11. CLOCK: It is used to set the time of day.

12. TIMER

13. MORE/LESS: Used to change the cooking time &

desired weight.

14. NUMBER: These used to set for time of day, cooking

time, power level, or defrost weight.

15. TIME: Touch this pad to set a cook time.

16. POWER: You can select power level for cooking.

17. ADD MINUTE

18. STOP/CLEAR: It used to stop oven and clear all

entries except time of day.

19. START/Q-START: To quickly set the cooking time

directly.

Keep Moisture

4 5

Only for training and service purposes

4-2

OPERATING SEQUENCE

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

1. CANCEL FUNCTION

Touch the STOP/CLEAR 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.

2. AUTO TOUCH

NOTE: • Heat only 1 package at a time

• Then the oven will start automatically.

3. TIME COOKING

4. MULTI-STAGE COOKING

You can program your oven to switch from one power level to another for up to 3 stages. To set a 2-stage cook cycle.

■ 1ST STAGE

■ 2ND STAGE

5. AUTO DEFROST COOKING

6. CHILD LOCK

This oven has a CHILD LOCK feature TO SET CHILD LOCK

• Touch STOP/CLEAR pad

• Touch and hold STOP/CLEAR pad LOCKED

appears on the display.

TO CANCEL CHILD LOCK

• Touch and hold STOP/CLEAR pad LOCKED

disappears.

7. MORE / LESS

The cook time is adjustable by MORE pad or LESS pad

8. AUTO REHEAT

NOTE: Then the oven will start automatically.

9. Q UICK DEFROST

10. AUTO COOK

NOTE: Then the oven will start automatically.

11. BREAKFAST MENU

STOP/CLEAR

POPCORN NUMBER OF TABLE

STOP/CLEAR

TIME

NUMBER

POWERNUMBER

START

STOP/CLEAR

TIME

NUMBER

POWERNUMBER

TIME

NUMBER

POWERNUMBER

START

STOP/CLEAR

STOP/CLEAR COOKING MORE/LESS

STOP/CLEAR

AUTO

REHEAT

NUMBER OF TABLE

STOP/CLEAR QUICK DEFROST

AUTO

DEFROST

NUMBER

NUMBER OF

WEIGHT

START

STOP/CLEAR AUTO COOK

NUMBER OF TABLE

STOP/CLEAR

BREAKFAST

NUMBER OF TABLE

Only for training and service purposes

SCHEMATIC DIAGRAM

4-3

Only for training and service purposes

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.

• 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.

• 3.3 volts AC is generated from the filament winding of

the high voltage transformer. This 3.3 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 4000 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 cut off the 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 fail to open, the fuse opens due to the large current surge caused by the monitor switch activation, which in turn stops magnetron oscillation.

4-4

CIRCUIT DESCRIPTION

FUSE

H.V.

TRANS-

FORMER

RELAY 2

MICOM CONTROLLER

SECONDARY SWITCH

PRIMARY SWITCH

MONITOR

SWITCH

FUSE

PRIMARY SWITCH

H.V.

TRANS-

FORMER

RELAY 2

MICOM CONTROLLER

SECONDARY SWITCH

MONITOR

SWITCH

Only for training and service purposes

+ 23 hidden pages

LG MS3846VRL Service Manual

Specifications and Main Features

Frequently Asked Questions

User Manual