LG LRM9000 Service Manual

MICROW AVE OVEN

SER VICE MANUAL

MODEL : LTM9000W/LTM9000B

CAUTION

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

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CAUTION

WARNING TO SERVICE TECHNICIANS

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 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 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.

• Proper operation of the microwave ovens requires that the magnetron be assembled to the wave guide 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.

• Routine service safety procedures should be exercised at all times.

• Untrained personnel should not attempt service without a thorough review of the test procedures and safety information contained in this manual.

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FOREWORD

Read this Manual carefully. Failure to adhere to or observe the information in this Manual may result in exposing yourself to the Microwave Energy normally contained within the oven cavity.

MECHANICAL SERVICE INFORMATION

TABLE OF CONTENTS

1. Adjustment Procedures....................................................................................................................................... 3

2. Precautions on Installation .................................................................................................................................. 5

3. General Precautions in Use................................................................................................................................. 5

4. Trial Operation..................................................................................................................................................... 5

5. Features and Specifications................................................................................................................................ 6-7

6. Overall Circuit Diagram ....................................................................................................................................... 8-9

7. Operating Procedures ......................................................................................................................................... 10-11

8. Procedure for Measuring Microwave Energy Leakage........................................................................................ 12-13

9. Disassembly Instructions..................................................................................................................................... 14-17

10. Interlock Continuity Test.................................................................................................................................... 18

11. Test and Checkout Procedures, and Troubleshooting

A. Test Procedures............................................................................................................................................. 19-22

B. Checkout Procedures..................................................................................................................................... 23-25

C. Troubleshooting............................................................................................................................................. 26-31

12. Exploded View................................................................................................................................................... 32-38

13. Replacement Parts List ..................................................................................................................................... 39-42

14. Schematic diagram of P.C.B .............................................................................................................................43

A. Printed circuit board.......................................................................................................................................44-45

15.P.C.B Parts List..................................................................................................................................................46-48

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1. ADJUSTMENT PROCEDURES

To avoid possible exposure to microwave energy leakage, adjust the door latches and interlock switches, using the following procedure.

ONLY AUTHORIZED SERVICE PERSONNEL SHOULD MAKE THIS ADJUSTMENT.

The Interlock Monitor and Primary Interlock Switch acts as the final safety switch protecting the user from microwave energy. The terminals between “COM” and “NC” of the Interlock Monitor must close when the door is opened. After adjusting the Interlock Monitor Switch, make sure that it is correctly connected. See Figures 1-a and 1-b throughout this procedure.

CHECK THE DOOR LATCH AND SWITCH CLOSING.

NOTE: The outer cover of the microwave oven is

removed.

(1) Set the microwave oven on its side so that you can see

the latch board and the switches, as shown in Figure 1-a.

(2) Close the door tightly and check gaps A and B to be

sure they are no more than 1/64” (0.5 mm). See Figure

1-b for close-up view of gaps A and B (door latches). If all gaps are less than 1/64” (0.5 mm), adjustment of the latch board may not be necessary. Go to Steps 5 and 6 to check the sequence of the switches.

NOTE: To correct sequence of the Primary Interlock

Switch, Secondary Interlock Switch and the Interlock Monitor Switch is very important.

If any gap is larger than 1/64” (0.5 mm), you will need to adjust the latch board-U, L. Go to step 3 and follow all steps in order.

ADJUST THE LATCH AND SWITCH CLOSING

(3) Loosen the two screws holding the plastic latch board as

shown.

(4) With the oven door closed tightly, move the latch board

upward toward the top of the oven and/or away from the door latch until the gaps are less than 1/64” (0.5 mm).

Hold the latch board tightly in this position until you check the sequence of the switches in steps 5 and 6.

TEST THE LATCH AND SWITCH SEQUENCE

(5) Open the oven door slowly. Watch the door latch, the

Primary Switch. Release Rod and Lever on the switches to make sure they are zero to the body of the switches in the following sequence:

- Primary Interlock Switch

- Secondary Interlock Switch

- Interlock Monitor Switch

Adjust the latch board until the switches operate in this sequence. See Steps 3 and 4.

(6) Close the oven door slowly and be sure it is tightly

closed. Watch the three switches to make sure they are zero to the body of the switches in the following sequence:

- Interlock Monitor Switch

- Primary Interlock Switch

- Secondary Interlock Switch

NOTE: The Interlock Monitor Switch is an added safety

check on the Primary and Secondary Interlock Switches. If the Primary and Secondary Interlock Switches allow the oven to operate with the door open, the Monitor Switch will blow the fuse.

(7) When you achieve the proper sequence of switches in

Steps 5 and 6, tighten the latch board screws at that point.

TEST THE MICROWAVE ENERGY LEAKAGE

(8) Using a survey meter, make sure the microwave energy

is below 5 mW/cm.sq.

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LATCH

LATCH BOARD

0-1/64"

Latch Board

Secondary Interlock Switch

Interlock Monitor Switch

Primary Interlock Switch

Figure 1-a

Figure 1-b

2. PRECAUTIONS ON INSTALLATION

(Figure 2)

A. Plug the power supply cord into a 120 V AC, 60 Hz,

single-phase power source with a capacity of at least 20 amperes.

B. Since the unit weights about 34 lbs, be sure to place it

on a sturdy and flat surface.

C. Avoid placing the unit in a location where there is direct

heat or splashing water.

D. Place the unit as far away as possible from TV, radio,

etc. to prevent interference. And do not place on or near a hot gas or electric burner or in a heated oven.

CAUTION

3. GENERAL PRECAUTIONS IN USE Microwave Oven

A. Never operate the unit when it is empty. Operating the

oven with no load may shorten the life of the magnetron. Whenever cooking dry foods (dried fish, bread, etc.) or a small amount of food, be sure to put a glass of water into the cooking compartment. The turntable tray may become hot after operating, be careful when touching it.

B. Aluminum foil should be avoided because it will disrupt

cooking and may cause arcing. However, small pieces may be used to cover some parts of food to slow the cooking. Any aluminum foil used should never be closer than 2.5 cm to any side wall of the oven.

Toaster

A. Never operate the toaster when it is empty. Operating

the toaster with no load may overheat this appliance.

B. Oversized food, metal foil packages or utensils must not

be inserted in this toaster, as they may create a fire or electrical hazards.

4. TRIAL OPERATION

After installation, the following sequences and results should be checked carefully.

Microwave Oven

A. Put a container filled with water (about 1 liter) into the

oven, and close the door tightly. B. Touch the STOP/CLEAR and the COOK TIME keys. C. Set cooking time for 10 minutes by touching “1”

and then “0” three times. “1000” appears in the

display window. D. Touch the START key.

Make sure the cavity light comes on. The unit will begin

cooking and the display window will show the time

counting down by seconds. E. After about 5 minutes, make sure the primary interlock

switch, the secondary interlock switch and the interlock

monitor and oven lamp switch operate properly by

opening and closing the door several times. Touch the

START key each time the door is closed. F. Continue operating the unit. Four long beep sound

signal is heard when the time is up. The unit will shut off

automatically. G. Confirm the water is hot. H. Finally, measure the output power according to

“POWER OUTPUT MEASUREMENT” on page 13.

Toaster

A. Make sure the crumb tray is pushed all the way in place

plugging in.

B. Remove all protective wrappings from food before

placing into toasting slots. Then place bread into slots

and close the door. C. Select one mode(Toast/Bagel). D. Press the Darkness Control to the desired setting. E. Press the Start button. Make sure indicator light comes

on. The unit will begin cooking and the display will show

the browning level you selected. F. After 1 minute, make sure the toaster door switch and

indicator light operate properly by opening and closing the door several times (In normal state, indicator light blinks when door is opened).

G. Continue operating the unit by pressing the Start button.

Beep sound signal is heard when the time is up. The unit will shut off automatically and fan will blow for 1 minute to cool this toaster.

H. Confirm the bread is cooked.

NOTE : If you operate this toaster for the first time, you will

notice an odor, that is a characteristic of burning off residues on the new heating elements. This is normal.

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This unit is equipped with a 3-prong plug for your safety. If the wall outlet is a grounded 3-hole type, the unit will be grounded automatically.

Three-Pronged(Grounding) Plug

Figure 2

Properly Polarized and Grounded Outlet

5. FEATURES AND SPECIFICATIONS

Microwave Oven

A. The safety systems incorporated in this oven are:

(1) Primary interlock switch (2) Secondary interlock switch (3) Interlock monitor switch (4) Choke system (5) Oven cavity thermostat

(Note: This thermostat located on the oven cavity will open and stop the unit from operation only if a high temperature is reached, such as, a fire created by overcooking food.)

B. Any one of 10 power output levels ranging 100W to

900W can be selected by the touch control and electronic computer system.

C. Cooking time can be displayed on the digital readout.

And MWO mode and Toaster mode can be displayed to avoid confusion.

D. Three different cooking stages can be set. The oven

remembers three cooking stages and changes from one cooking stage to another. This is made possible with the memory function of the microprocessor.

Toaster

A. The safety systems incorporated in this toaster are:

(1) Toaster door switch (2) Toaster thermostat

(Note : This thermostat located on the air tunnel will

open and stop the unit from operation only if a high temperature is reached, such as, a fire created by overcooking food.)

B. Cooking mode (Toast/Bagel) and browning level can be

displayed on the digital readout.

C. Thermister controls the toasting time by detecting the

internal temperature. This makes it possible to cook bread evenly.

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SPECIFICATIONS

Rated Power Consumption..........................................1350W

Output

Microwave oven ......................................................900W (

IEC 60705 Rating standard)

Adjustable 100W through 900W, 10 steps

Toaster.....................................................................800W

Frequency....................................................................2,450 MHz ± 50 MHz

Power Supply...............................................................120V ±12V AC, 60Hz

Rated Current...............................................................11.5 Amp.

Magnetron & Heater Cooling........................................Forced Air Cooling

Microwave Stirring........................................................Turntable

Rectification..................................................................Rectification Voltage Doubler Half-Wave

Door Sealing ................................................................Choke System

Safety Devices

Microwave oven ......................................................Thermostat : Open at 110°C ± 5°C, Close at 60°C ± 5°C

Fuse(15A) Primary Interlock Switch Secondary Interlock Switch Interlock Monitor

Toaster.....................................................................Toaster Door Switch

Thermostat : Open at 145°C ± 5°C, Close at 60°C ± 5°C

Magnetron....................................................................2M214

High Voltage Capacitor................................................Capacitor: 0.95µF, 2.1KV Ac

High Voltage Diode......................................................350mA, 9.0KV

Cavity Lamp.................................................................125V, 20W

Timer............................................................................Digital, up to 99 mm. 99 sec. (in each cooking stage)

Tray..............................................................................Tempered Safety Glass

Thermistor, NTC...........................................................150°C ± 3%

Crumb Tray..................................................................Crumbs of bread lay on it

Overall Dimensions......................................................21

/16”(W) x 123/16”(H) x 169/16”(D)

Oven Cavity Size..........................................................13

/2”(W) x 811/16”(H) x 143/16”(D)

Effective Capacity of Oven Cavity................................0.9 Cu.ft.

Accessories..................................................................Use and Care Manual ,Turntable,

Rotating Ring Assembly.

SWITCH TABLE

NOTE: Use the above switch table with circuit diagram on page 8.

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PRIMARY SECONDARY INTERLOCK TOASTER

INTERLOCK INTERLOCK MONITOR DOOR

SWITCH SWITCH SWITCH SWITCH

COM COM COM COM

NO NO NC NO

SWITCH MODE

CONDITIONS

DOOR OPEN

DOOR CLOSED

∞∞∞0

∞

6. OVERALL CIRCUIT DIAGRAM A. SCHEMATIC DIAGRAM

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

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

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 BASIC SCHEMATIC DIAGRAM, THE VALUES OF COMPONENTS AND

SOME PARTIAL CONNECTIONS ARE SUBJECT TO CHANGE FOR IMPROVEMENT.

Figure 3

B. MATRIX CIRCUIT FOR TOUCH KEY BOARD

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Figure 4

STOP/

CLEAR

START CLOCK Ez-ON

KITCHEN

TIMER

AUTO

DEFROST

DINNER

PLATE

POPCORN

POTATO

DARKER

LIGHTER

2345 6

890

STOP/

CLEAR

TOAST BAGEL START

COOK

TIME

POWER

: Toaster Key

BEVERAGE

FRESH

VEGETABLE

FROZEN ENTREE

7. OPERATING PROCEDURES A. OVEN CONTROL PANEL

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NOTE: A “beep” sounds when you touch a “key” on the control panel, to indicate that you have entered

a setting.

1. Toast. Toast bread

2. Bagel. Toasts Bagels

3. Stop/Clear. Touch this pad to stop the toaster or clear entries.

4. Start. Touch this pad to start the toasting process.

5. Darkness Control. Adjust darkness control to desired setting before cooking foods.

(Default : 5, "1" is the lightest and "9" is the darkest)

6. Indicator Light. When operating toaster with door closed, this will be illuminated. If you open the door during toasting, this will blink.

TOASTER CONTROL AREA

5 42

1 35

1. DISPLAY. The Display includes a clock and indicators that tell you time of day, cooking time settings, and cooking functions selected.

2. STOP/CLEAR. Touch this pad to stop the oven or clear entries.

3. START. Touch this pad to start all entries (except the Auto Cook and Add Minute function which start

automatically) and to turn Child Lock on or off.

4. AUTO COOK. Touch this pad to select programming food items.

5. Ez-ON. Touch this pad to cook at 100% cook power for 1 minute to 99 minutes 59 seconds.

6. AUTO DEFROST. This pad is an accurate defrosting method for frozen meat, poultry and fish up to 6.0 lbs.

7. COOK TIME. Touch this pad to set a cooking time.

8. POWER. Touch this pad to set a cooking power.

9. CLOCK. Touch this pad to set the time of day.

10. KITCHEN TIMER. Touch this pad to use your microwave oven as a kitchen timer.

11. NUMBER PADS. Touch Number Pads to enter cooking time, power level, quantities, or weights.

MICROWAVE CONTROL AREA

10 7 8 3

6 5 24

B. EASY USE TABLE

MICROWAVE OVEN

(1) KITCHEN TIMER

1. Touch STOP/CLEAR.

2. Touch KITCHEN TIMER.

3. Touch correct number for time.

4. Touch START.

(2) CHILD LOCK

To set:

1. Touch STOP/CLEAR.

2. Touch “START” more than 4 seconds. To cancel:

1. Touch STOP/CLEAR.

2. Touch “START” more than 4 seconds.

(3) AUTO COOK

1. Touch STOP/CLEAR.

2. Touch AUTO COOK Category.

3. Touch START. (Although you don’t touch start, it will start after

4 seconds automatically)

(4) Ez-ON

1. Touch STOP/CLEAR.

2. Touch Ez-ON.

(5) AUTO DEFROST

1. Touch STOP/CLEAR.

2. Touch AUTO DEFROST. Three different defrosting levels are provided. (Touch 1 : Meat

Touch 2 : Poultry Touch 3 : Fish)

3. Enter the weight of your food in decimal increments from 0.1 to 6.0 pounds.

4. Touch START

5. At beeping, turn food over by following the instructions in the manual.

6. After turning food over, touch START to resume defrosting.

(6) TIMED COOKING

1. Touch STOP/CLEAR.

2. Touch COOK TIME.

3. Touch number for cooking time.

4. Touch POWER.

5. Touch number for cooking power level.

6. Touch START.

(7) MULTI-STAGE COOKING

1. Touch STOP/CLEAR.

2. Touch COOK TIME.

3. Touch number for cooking time.

4. Touch POWER.

5. Touch number for cooking power level.

6. Repeat steps 2-5 to set 2nd cooking stage.

7. Touch START.

TOASTER

(1) TOAST

1. Touch STOP/CLEAR.

2. Touch TOAST.

3. Touch Darkness Control (1~9 step)

4. Touch START.

(2) BAGEL

1. Touch STOP/CLEAR.

2. Touch BAGEL.

3. Touch Darkness Control (1~9 step)

4. Touch START.

(3) DARKNESS SETTINGS

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Degree of darkness Select darkness level

Light 1~3

Medium 4~6

Dark 7~9

8. PROCEDURE FOR MEASURING MICROWAVE ENERGY LEAKAGE

A. CAUTIONS

(1) Be sure to check a microwave emission prior to servicing

the oven if the oven is operative prior to servicing.

(2) 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 5mW/cm.sq. and 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.

(3) 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 Health 1390 Piccard Drive Rockville, Maryland 20850

(4) The service personnel should check all surface and vent

openings for microwave emission testing.

(5) Check for microwave energy leakage after every

servicing. The power density of the microwave radiation leakage emitted by the microwave oven should not exceed 1mW/cm.sq. And always start measuring of an unknown field to assure safety for operating personnel from radiation leakage. NOTE: The standard is 5mW/cm.sq. while in the customer’s home. 1mW/cm.sq. stated here is manufacturer’s own voluntary standard for units in customer’s home.

EQUIPMENT

• Electromagnetic energy leakage monitor (NARDA 8100B, HOLADAY HI 1501)

• 600cc glass beaker

• Glass thermometer 100°C

B. MEASURING MICROWAVE ENERGY LEAKAGE

(1) Pour 275±15cc of 20±5°C water in a beaker which is

graduated to 600 cc, and place the beaker in the center of the oven.

(2) Set the energy leakage monitor to 2,450 MHz and use it

following the manufacturer’s recommended test procedure to assure correct result.

(3) When measuring the leakage, always use the 2 inch

(5cm) spacer supplied with the probe. (4) Operate the oven at its maximum output. (5) Measure the microwave radiation using and

electromagnetic radiation monitor by holding the probe

perpendicular to the surface being measured. (See

Figure 6)

C. MEASUREMENT WITH THE OUTER CASE REMOVED

(1) When you replace the magnetron, measure for

microwave energy leakage before the outer case is

installed and after all necessary components are

replaced or adjusted. Special care should be taken in

measuring the following parts.

- Around the magnetron

- The waveguide

WARNING: AVOID CONTACTING ANY HIGH VOLTAGE

PARTS.

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Move probe along shaded area.

Probe scanning speed less than 2.5 cm/sec.

Figure 6

Figure 5

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