LG LRMM1430 Service Manual

MICROW AVE OVEN

SER VICE MANUAL

MODEL : LRMM1430SW

LRMM1430SB

CAUTION

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

website http://www.lgservice.com

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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.

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....................................................................................................................................... 3-4

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

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

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

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

6. Overall Circuit Diagram ....................................................................................................................................... 7-8

7. Operating Procedures ......................................................................................................................................... 9-11

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

9. Disassembly Instructions..................................................................................................................................... 14-18

10. Interlock Continuity Test.................................................................................................................................... 19

11. Test and Checkout Procedures, and Troubleshooting

A. Test Procedures............................................................................................................................................. 20-22

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

C. Troubleshooting............................................................................................................................................. 26-30

12. Exploded View................................................................................................................................................... 31-37

13. Replacement Parts List ..................................................................................................................................... 38-41

14. Schematic diagram of P.C.B ............................................................................................................................. 42

A. Printed circuit board....................................................................................................................................... 43

15.P.C.B Parts List.................................................................................................................................................. 44-46

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MODEL LRMM1430SW

LRMM1430SB

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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 CLOSINGS.

NOTE: The out case 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 CLOSINGS

(3) Loosen the screw 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 BOARD

PRIMARY INTERLOCK SWITCH

LATCH

LATCH BOARD

(A)

(B)

0-1/64"

DOOR LATCH

SECONDARY INTERLOCK SWITCH

MONITOR 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 38 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.

CAUTION

3. GENERAL PRECAUTIONS IN USE

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.

4. TRIAL OPERATION

After installation, the following sequences and results should be checked carefully. 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. “0”

appears in the display window.

C. Set cooking time for 10 minutes by touching “1” and

then “0” three times. “10:00” 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. Two short and a 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.

5. FEATURES AND SPECIFICATIONS

A. The safety systems incorporated in this model 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 0W to 1200W

can be selected by the touch control and electronic

computer system. C. Cooking time can be displayed on the digital readout. D. Three different cooking stages (Include Defrost) 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.

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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

Properly Polarized and Grounded Outlet

Figure 2

SPECIFICATIONS

Rated Power Consumption 1250W maximum Output

1200W maximum (*IEC 60705 Rating standard) Adjustable 0W through 1200W, 10 steps

Frequency 2,450 MHz

50 MHz

Power Supply 120V 12V AC, 60Hz Rated Current 11 Amp. Magnetron Cooling Forced Air Cooling Microwave Stirring Turntable Rectification Rectification Voltage Doubler Half-Wave (Inverter type) Door Sealing Choke System Safety Devices Thermostat:

Open at 90 ˚C 5 ˚C

Close at 75 ˚C 5 ˚C Fuse(20A) Primary Interlock Switch Secondary Interlock Switch Interlock Monitor

Magnetron 2M261 Cavity Lamp 125V, 20W Timer Digital, up to 99 mm. 99 sec. (in each cooking stage) Tray Tempered Safety Glass Overall Dimensions 20

/4”(W) x 151/4”(D) x 191/4”(H)

Oven Cavity Size 17

/4”(W) x 9”(D) x 163/4”(H)

Effective Capacity of Oven Cavity 1.4 Cu.ft. Accessories Owner’s Manual & Cooking Guide ,Turntable, Rotating Ring Assembly.

SWITCH CHART

NOTE: Use the above switch chart with circuit diagram on page 7.

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PRIMARY SECONDARY INTERLOCK INTERLOCK INTERLOCK MONITOR SWITCH SWITCH SWITCH

COM COM COM

NO NO NC

SWITCH MODE

CONDITIONS DOOR OPEN

DOOR CLOSED

∞

6. OVERALL CIRCUIT DIAGRAM A. SCHEMATIC DIAGRAM

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Figure 3

B. MATRIX CIRCUIT FOR TOUCH KEY BOARD

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Figure 4

7. OPERATING PROCEDURES A. CONTROL PANEL

Figure 5.

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

2. Sensor Touch. This pad allows you to cook most of your favorite foods without having to select cooking times and power levels.

3. Homemade Bakery. Homemade bakery has 3 food categories of preset cooking time and power level.

4. Chicken Choices. Chicken Choices has 4 food categories of preset cooking time and power level.

5. Soften. Touch this pad to soften ice cream, cream cheese, butter or frozen juice.

6. Children’s Lunch. Children’s Lunch has 3 food categories of preset cooking time and power level.

7. Fast Breakfast. Fast Breakfast has 3 food categories of preset cooking time and power level.

8. Melt. Touch this pad to melt chocolate, cheese, butter or marshmallows.

9. Auto Defrost. This pad is an accurate defrosting method for meat, poultry, fish and bread.

10. Q-Defrost. Touch this pad to defrost foods quickly.

11. More / Less. Touch these pads to adjust cooking

time in 10 second increments.

12. Cook time. Touch this pad to set a cooking time.

13. Power. Touch this pad to set a cooking power.

14. Clock. Touch this pad to enter the time of day.

15. Kitchen Timer. Touch this pad to use your

microwave oven as a kitchen timer.

16. Number pads. Touch Number pads to enter cooking time, Power level, quantities, or weights.

17. Stop/Clear. Touch this pad to stop the oven or clear entries. Also used to turn Child Lock on and off.

18. Ez-ON. You can extend cooking time in multiples of 30 seconds by repeatedly touching this pad during cooking.

19. Start. Touch this pad to start the oven.

12 3 4 5 9 12 14 16 17

6 7 8 10 13 15 18 1911

B. PANEL INSTRUCTIONS (Figure 5)

The entire operation is done by simple touch control pads.

(1) Display Window

Numbers and letters explained in Figure 5 are shown in the display window (Vacuum Fluorescent Tube).

(a) The Time in four digits (12-hour indication): 00 Hour

00 Minute.

(b) Cooking Time of Day in four digits 00 Minutes 00

Seconds. (c) Power Control Level in three digits: P-000 (d) Each Indicator Light shows which function is set and

involved in the course of cooking by turning itself on.

Indicator Lights automatically go out upon completion

of cooking.

(2) SENSOR COOK key

Use humidity sensor for certain food item.

(3) HOMEMADE BAKERY key

3 food categories of preset cooking time and power level. (Roll/Muffin, Pancake & French Toast)

(4) CHICKEN CHOICES key

4 food categories of preset cooking time and power level. (Chicken Wings, Chicken Nuggets, Spicy Chicken & Mexican Chicken )

(5) CHILDREN’S LUNCH key

3 food categories of preset cooking time and power level. (Hot Dog Buns, Frozen Pizza & Canned Pasta)

(6) FAST BREAKFAST key

3 food categories of preset cooking time and power level. (Oatmeal, Bacon & Scrambled Eggs)

(7) CLOCK Key

Used in setting Time of Day.

(8) COOK TIME Key

The TIME key is used to set the cooking time. Touch the TIME key and then the number keys that correspond to the desired cooking time. The remaining time is continuously displayed during cooking.

(9) STOP/CLEAR Key

Used to stop the oven or clear all entries except CLOCK.

(10) AUTO DEFROST key (DEFROST MEAT, POULTRY,

FISH & BREAD)

Used in setting AUTO DEFROST.

(11) Q DEFROST key

Used in setting QUICK DEFROST.

(12) KITCHEN TIMER Key

Used as a kitchen timer.

(13) POWER Key

Used to select cooking power level.

(14) Ez-ON Key

It will add 30 seconds up to 3 minutes 30 seconds: after 3 minutes 30 seconds, every touch will add 1 minute up to 99 minutes 59 seconds.

(15) START Key

Touch the START key after setting the desired cooking times etc. Also touch the START key to resume cooking after the cooking is temporarily stopped by opening the door. The key will not function unless the door is closed.

(16) Soften

Used to soften ice cream, cream cheese, butter or frozen juice.

(17) Melt

Used to melt chocolate, cheese, butter or marshmallows.

(18) More/Less

Used to adjust cooking time in 10 second increments.

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C. EASY USE CHART

(1) CLOCK

1. Touch STOP/CLEAR.

2. Touch CLOCK.

3. Touch numbers for correct time of day.

4. Touch CLOCK.

(2) “HI-POWER” COOKING

1. Touch STOP/CLEAR.

2. Touch COOK TIME.

3. Touch numbers for desired cooking time.

4. Touch START.

(3) “MULTI-STAGE” COOKING

1. Touch STOP/CLEAR.

2. Touch COOK TIME.

3. Touch numbers 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.

(4) CHILD LOCK

To set:

1. Touch STOP/CLEAR.

2. Hold STOP/CLEAR more than 2 seconds. To cancel:

1. Touch STOP/CLEAR.

2. Hold STOP/CLEAR more than 2 seconds.

(5) SOFTEN

1. Touch STOP/CLEAR.

2. Touch SOFTEN. Four different soften menus are provided.

3. Select Menu 1 to 4- See cooking guide.

4. Enter the amount of the Category.

(6) MELT

1. Touch STOP/CLEAR.

2. Touch MELT. Four different melt menus are provided.

3. Select Menu 1 to 4- See cooking guide.

4. Enter the amount of the Category.

(7) AUTO DEFROST

1. Touch STOP/CLEAR.

2. Touch AUTO DEFROST. Three different defrosting category are provided. (MEAT, POULTRY, FISH, BREAD)

3. Enter the weight of your food.

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.

(8) Q DEFROST

1. Touch STOP/CLEAR.

2. Touch Q DEFROST.

(9) KITCHEN TIMER

1. Touch STOP/CLEAR.

2. Touch KITCHEN TIMER.

3. Touch correct numbers for time.

4. Touch START.

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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 1000C

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

(5 cm) 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 7)

C. MEASUREMENT WITH THE OUT 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 7

Figure 6

D. MEASUREMENT WITH A FULLY ASSEMBLED OVEN

(1) After all components, including the outer panels, are

fully assembled, measure for microwave energy leakage around the door viewing window, the exhaust opening and air inlet openings.

(2) Microwave energy leakage must not exceed the values

prescribed below.

NOTES:

Leakage with the outer panels removed - less than 5mW/cm.sq. Leakage for a fully assembled oven (Before the latch switch (primary) is interrupted) with the door in a slightly opened position - less than 1 mW/cm .sq.

E. NOTE WHEN MEASURING

(1) Do not exceed meter full scale deflection. (2) The test probe must be removed no faster than 1

inch/sec (2.5cm/sec) along the shaded area, otherwise a false reading may result.

(3) The test probe must be held with the grip portion of the

handle. A false reading may result if the operator’s hand is between the handle and the probe.

(4) When testing near a corner of the door, keep the probe

perpendicular to the surface making sure the probe horizontally along the oven surface, this may possibly cause probe damage.

F. RECORD KEEPING AND NOTIFICATION AFTER

MEASUREMENT

(1) After adjustment and repair of any microwave energy

interruption or microwave energy blocking device, record the measured values for future reference. Also enter the information on the service invoice.

(2) Should the microwave energy leakage not be more

than 1mW/cm.sq. after determining that all parts are in good condition, functioning properly and genuine replacement parts which are listed in this manual have been used.

(3) At least once a year, have the electromagnetic energy

leakage monitor checked for calibration by its manufacturer.

G. POWER OUTPUT MEASUREMENT

Be sure oven cavity is clean and cool . (not used recently)

(1) Fill the test beaker with 59 ˚F(15 ˚C) ~ 75 ˚F(24 ˚C) 1 liter tap

water.

(2) Stir the water in the beaker with thermometer (˚F or ˚C) and

measure temperature as T1. (3) Place the beaker on the center of turntable. (4) Set for one (1) minute. (5) When the heating is finished, stir the water again with

thermometer and measure the temperature of water as T2. (6) Subtract T1 from T2, this will give you the temperature rise. (7) The microwave power output is within specification, if the

temperature rise is as shown below:

(8) Power output will be influenced by line voltage of power

supply. Consequently, correct power output must be

measured within 120V AC 1 Volt while unit is operating.

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SPECIAL TIP

• This oven used the button head screws.

• When you remove the screws, using the tamper-resistant Torx driver have a pin-in-head.

Voltage Temperature Rise

(VAC under load) °C °F

120V 13 - 15 23.4 - 27 108V 11.5 - 13.5 20.7 - 24.3

Button Head

(Torx style 2)

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9. DISASSEMBLY INSTRUCTIONS

IMPORTANT NOTES:

UNIT MUST BE DISCONNECTED FROM ELECTRICAL OUTLET WHEN MAKING REPAIRS, RE-PLACEMENTS, ADJUSTMENTS AND CONTINUITY CHECKS. WAIT AT LEAST ONE MINUTE, UNTIL THE HIGH VOLTAGE CAPACITOR IN THE HIGH VOLTAGE POWER SUPPLY HAS FULLY DISCHARGED. THE CAPACITOR SHOULD BE DISCHARGED BY USING INSULATED WIRE - I.E. TEST PROBE CONNECTED TO 10K-OHM RESISTOR IN SERIES TO GROUND. WHEN RECONNECTING THE WIRE LEADS TO ANY PART, MAKE SURE THE WIRING CONNECTIONS AND LEAD COLORS ARE CORRECTLY MATCHED ACCORDING TO THE OVERALL CIRCUIT DIAGRAM. (ESPECIALLY SWITCHES AND HIGH VOLTAGE CIRCUIT.)

A. REMOVING OUT CASE (Figure 8)

(1) Unfasten five screws from the rear section. (2) Unfasten two screws from the side section. (3) Push the out case back about 1 inch (3cm). (4) Lift the case from the set.

B. DOOR ASSEMBLY REMOVAL (

Figure 9)

(1) Remove out case. (2) Unfasten two screws for removing deco front. (3) Disconnect the lead wires from main board and pull that out

from the cavity.

(4) Remove the choke cap very carefully with a flat-blade screw

driver.

(5) Lift up and pull out Door assembly carefully from the cavity.

CAUTION: Be careful not to damage door seal plate with

the screw driver.

Figure 8

Remove choke cap

Disconnect the lead wires

Remove deco front

Remove door

Figure 9

Choke Cap

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