Kenmore 721.62253, 721.62252, 721.62253201, 721.62259 Service Manual

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MODEL 721.62252

721.62259

721.62253

721.63263

DIVISION 20

BASIC FIELD MANUAL

FOR

MICROWAVE OVEN

MODEL 721.62252200 / 721.62252201

721.62259200 / 721.62259201

721.62253200 / 721.62253201

721.63263300 / 721.63263301

May, 2005

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.

-1-

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.

MODEL 721.62252

721.62259

721.62253

721.63263

MECHANICAL SERVICE INFORMATION

TABLE OF CONTENTS

1. Adjustment Procedures

2. Precautions on Installation

3. General Precautions in Use

4. Trial Operation

5. Specifications

6. Overall Circuit Diagram

7. Operating Procedures

8. Procedure for Measuring Microwave Energy Leakage

9. Disassembly Instructions

10. Interlock Continuity Test

11. Test and Checkout Procedures, and Troubleshooting

A. Test Procedures

B. Checkout Procedures

C. Troubleshooting

12. Exploded View

13. Part Reference list

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7-9

10-11

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12-13

14-18

20-22

23-25

26-30

31-41

42-49

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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.

ADJUST THE LATCH AND SWITCH CLOSINGS

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

shown.

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 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.

(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.

-3-

LATCH BOARD

MONITOR INTERLOCK SWITCH

PRIMARY INTERLOCK SWITCH

SECONDARY INTERLOCK SWITCH

LATCH

LATCH BOARD

0-1/64"

DOOR LATCH

Figure 1-a

Figure 1-b

-4-

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 15 amperes.

B. Since the unit weights about 26 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

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.

Properly Polarized and Grounded Outlet

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. 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.

Three-Pronged(Grounding) Plug

Figure 2

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.

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) Magnetron thermostat

(6) 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

1000W 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 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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SPECIFICATIONS

Rated Power Consumption Output

Frequency Power Supply Rated Current Magnetron Cooling Microwave Stirring Rectification Door Sealing Safety Devices

Magnetron High Voltage Capacitor High Voltage Diode Cavity Lamp Timer Tray Overall Dimensions

Oven Cavity Size

Effective Capacity of Oven Cavity Accessories

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1450W maximum 1100W maximum (*IEC60705 Rating standard) Adjustable 110W through 1100W, 10 steps 2450 MHz ± 50 MHz 120V AC, 60Hz

12.5 Amp. Forced Air Cooling Turntable Rectification Voltage Doubler Half-Wave Choke System Thermostat:

Open at 90°C ± 5°C

Close at 75°C ± 5°C Fuse(20A) Primary Interlock Switch Secondary Interlock Switch Interlock Monitor 2M282J Capacitor: 1.05µF, 2.1 KV Ac 350mA, 9.0 KV 125 V, 20 W Digital, up to 99 mim. 99 sec. (in each cooking stage) Tempered Safety Glass 203/19"(W) x 1117/20"(H) x 1621/46"(D)

1413/75"(W) x 910/27"(H) x 15"(D)

1.2 Cu.ft. Use and Care Manual ,Turntable, Rotating Ring Assembly.

SWITCH CHART

PRIMARY SECONDARY INTERLOCK

SWITCH MODE

CONDITIONS

DOOR OPEN

DOOR CLOSED

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

INTERLOCK INTERLOCK MONITOR

SWITCH SWITCH SWITCH

COM COM COM

NO NO NC

∞∞0

00∞

-6-

6. OVERALL CIRCUIT DIAGRAM

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.

SYMBOL

NOTE:

1. DOOR IS OPEN.

2.RS: SENSING ELEMENT RC: COMPENSATING ELEMENT

3. WIRE COLOR.

COLOR WHITE BLACK

YELLOW PINK

BLUE

GREEN BROWN

YL PK

RED

GN BN

WH RD

RC RS

HUMIDITY

SENSOR

321

A (I). SCHEMATIC DIAGRAM *Check the Model No.

-7-

A (II). SCHEMATIC DIAGRAM *Check the Model No. (ADD Noise filter)

-8-

B. MATRIX CIRCUIT FOR TOUCH KEY BOARD

Figure 4

-9-

7. OPERATING PROCEDURES

Figure 5

A. OVEN 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. QUICK TOUCH SENSOR. This pad allows you to cook most of your favorite foods without having to select cooking times and power levels.

3. AUTO DEFROST. This pad is an accurate defrosting method for frozen meat, poultry and fish up to 6.0 lbs or 4.0 kgs.

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

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

6. STOP/CLEAR. Touch this pad to stop the oven or

clear entries.

7. EXPRESS DEFROST. This pad provides you with the quick defrosting method for 1.0 pound frozen foods.

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

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

10. CLOCK. Touch this pad to enter the time of day.

11. OPTION. Touch this pad to change the oven's default

settings for sound, clock, scroll speed and Lbs/Kg.

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

13. ADD MINUTE. Touch this pad to cook at 100% cook

power for 1 minute to 99 minute 59 seconds.

14. START. Touch this pad to start all entries (except the

Quick Touch Sensor, Express Defrost, Auto Cook and Add Minute function which start automatically) and to turn Child Lock on or off.

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

a setting.

-10-

B. EASY USE TABLE

(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) QUICK TOUCH SENSOR

1. Touch STOP/CLEAR.

2. Touch QUICK TOUCH SENSOR Category.

(4) ADD MINUTE

1. Touch STOP/CLEAR.

2. Touch ADD MINUTE.

(5) OPTION

1. Touch STOP/CLEAR.

2. Touch OPTION.

3. Touch number from 1 to 4 Touch 1: SOUND ON/OFF Touch 2: CLOCK ON/OFF Touch 3: SCROLL SPEED Touch 4: LBS/KG

(8) TIMED 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. Touch START.

(9) 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.

(6) EXPRESS DEFROST

1. Touch STOP/CLEAR.

2. Touch EXPRESS DEFROST.

(7) 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.

-11-

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 2450 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)

Move probe along shaded area.

Probe scanning speed less than 2.5 cm/sec.

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

Figure 6

WARNING: AVOID CONTACTING ANY HIGH VOLTAGE

PARTS.

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