Kenmore 721.67903, 721.67902, 721.67909 Service Manual

삼 흥

정 판

MODEL 721.67902

721.67903

721.67909

DIVISION 20

BASIC FIELD MANUAL

FOR

MICROWAVE OVEN

MODEL 721.67902600

721.67903600

721.67909600

JUNE, 2006

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.

CONTENTS

MODEL 721.67902

721.67903

721.67909

(Page)

SAFETY PRECAUTIONS

SPECIFICATIONS

CAUTIONS

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INSTALLATIONS

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OPERATING INSTRUCTIONS

FEATURES

CONTROL PANEL

OPERATING SEQUENCE

SCHEMATIC DIAGRAM

CIRCUIT DESCRIPTION

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SERVICE INFORMATION

TOOLS AND MEASURING INSTRUMENTS

MICROWAVE LEAKAGE TEST

MEASUREMENT OF MICROWAVE POWER OUTPUT

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Inside front cover

1-1

2-1

3-1

4-1

4-2

4-3

4-4

5-1

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5-3

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

5-8

5-9

5-14

6-1

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7-1

SPECIFICATIONS

Rated Power Consumption Output

Microwave

Convection

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

Magnetron High Voltage Capacitor High Voltage Diode Cavity Lamp Tray

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Overall Dimensions

Oven Cavity Size

Effective Capacity of Oven Cavity Accessories

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1500W

1000W (*IEC60705 Rating standard) Adjustable 100W through 1000W, 10 steps 1500W 1500W 2450 MHz 120 V AC, 60 Hz 13 Amp. Forced Air Cooling Turntable Rectification Voltage Doubler Half-Wave Choke Cover and 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 Switch 2M246 Capacitor: 1.0 µF, 2.1 KV AC 350 mA, 9.0 KV 125 V, 20 W Tempered Safety Glass 225/8"(W)x20"(H)x147/8"(D)

/4"(W)x151/4"(H)x107/8"(D)

1.5 Cu.ft. Use and Care Manual, Glass Turntable, Rotating Ring, Metal Rack

SWITCH CHART

PRIMARY

SWITCH MODE

CONDITIONS

DOOR OPEN DOOR CLOSED

NOTE: Use the above switch chart with circuit diagram on page 4-4.

“•” represents the connection of the terminal of each switch.

INTERLOCK

SWITCH

COM

••

1-1

SECONDARY

INTERLOCK

SWITCH

COM

INTERLOCK

MONITOR

SWITCH

COM

•

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 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.

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 connected. All input and output microwave connections, waveguide, flange, and gasket must be secured 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 TECHNICIANS.

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, dents inside the cavity, or on the exterior.

2. Put the oven on a counter, table, or shelf at least

39.4 inches(100cm) from floor 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 2 inches(5 cm) from the wall.

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

ENSURE PROPER GROUND

EXISTS BEFORE USE

7. Place the microwave oven as far away as possible from TV, RADIO, COMPUTER, TELEPHONE, etc., to prevent interference.

5cm

Counter,

100cm

table, shelf

3-1

FEATURES

Metal Rack

Oven Front Plate

Window Door Screen

Door Seal

Safety Interlock System

Control Panel

Display Window

Glass Tray

Rotating Ring

CONTROL PANEL

OPERATING INSTRUCTIONS

1. DISPLAY. The Display includes a clock and indicators to tell you time of day,

cooking time settings and cooking functions selected.

2. MICRO. Touch this pad when setting microwave cooking.

3. CONV. Touch this pad to operate the oven for convection cooking only.

4. COMBI. Touch this pad to program the amount roasting time and heat for a

cooking cycle using both microwave energy and convection energy.

5. CONVECTION AUTO BAKE. Touch this pad to automatically bake frozen pizza,

muffins, biscuits and frozen French fries using both microwave and convection energy alternately.

6. CONVECTION AUTO ROAST. Touch this pad to automatically roast beef, chicken,

turkey breasts and pork using both microwave and convection energy alternately.

7. SENSOR COOK. Touch this pad to cook 10 types of foods. The oven's sensor

will tell the oven how long to cook depending on the amount of humidity coming from the food.

8. SENSOR POPCORN. Touch this pad when popping commercially packaged

popcorn in your microwave oven. The oven's sensor will tell the oven how long to cook depending on the amount of humidity it detects from the popcorn.

9. SENSOR REHEAT. Touch this pad to reheat precooked, room-temperature or

refrigerated foods. The oven's sensor will tell the oven how long to cook depending on the amount of humidity coming from the food.

10. AUTO DEFROST. Touch this pad once to automatically defrost Meat, Poultry,

Fish or Bread according to weight. Touch this pad twice to defrost most other frozen foods by time.

11. EXPRESS DEFROST. Touch this pad for rapid defrosting of one pound of

frozen food.

12. WARM HOLD. Touch this pad to keep hot, cooked foods warm in your

microwave oven.

13. MORE. Touch this pad to add 10 seconds of cooking time each time it is pressed.

14. LESS. Touch this pad to subtract ten seconds of cooking time each time it is

pressed.

15. NUMBER. Touch number pads to enter cooking times, cook powers, quantities,

weights, or food categories.

16. ADD MINUTE. Touch this pad to set and start cooking at 100% power.

17. POWER. Touch this pad to select a cooking power level.

18. STOP/CLEAR. Touch this pad to cancel a currently running program or erase a

cooking cycle being programmed.

19. START/PAUSE. Touch this pad to start a program or to pause the oven during

cooking or defrosting.

20. OPTION. Touch this pad to change the oven's default settings for volume, clock,

scroll speed, units of weight and language.

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

22. KITCHEN TIMER. Touch this pad to set the kitchen timer.

4-1

OPERATING SEQUENCE

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

1. SETTING THE CLOCK

Stop/ Clear

START/PAUSE and CANCEL FUNCTION

1) Touch Start/Pause pad to start oven or pause the oven temporarily during cooking.

2) Touch Clear pad to cancel a program during cooking or Erase during programming.

Clock

Enter time

of day

Start/Pause

3. KITCHEN TIMER.

Stop/Clear Kitchen Timer

Enter time

Start/Pause

4. CHILD LOCK

TO SET CHILD LOCK

• Touch and hold START/PAUSE pad

• Touch and hold START/PAUSE pad LOCKED appear on the display.

TO CANCEL CHILD LOCK

• Touch and hold START/PAUSE pad LOCKED disappear in the display.

5. WARM HOLD

Stop/ Clear

Warm Hold

Start/Pause

6. MORE / LESS

• The More and Less functions will adjust the cook time of many oven functions.

• More/Less will add/subtract 10 seconds to the cook time each time you press it.

NOTE:

• For convection cooking, More and Less are used as temperature selection pads.

7. MICRO COOKING

Micro

Power

Level

Cooking time

Start/Pause

Power

8. MULTI-STAGE COOKING

1ST STAGE

Micro Power

2ND STAGE

Micro Power

Power Level

Cooking

Enter

time

Cooking

time

Start/Pause

Enter Power

Level

To keep hot, cooked food warm.

4-2

OPERATING SEQUENCE

9. SENSOR TOUCH COOKING

• Sensor cook and reheat

Stop/

Clear

• Sensor Popcorn

Stop/

Clear

Sensor Cook

Sensor Reheat

Popcorn

Select Sensor

10. AUTO DEFROST

Stop/

Clear

Stop/

Clear

Auto

Defrost

Enter the

Weight

Auto

Defrost

Select Food

Category

Food Category

Start/Pause

Select

Temperature

Start/Pause

TO COOK(After preheating)

Cooking Time

Start/Pause

14. COMBINATION

Stop/ Clear

Combi

Start/Pause

Cooking Time

4-3

SCHEMATIC DIAGRAM

NOTE:

1. DOOR IS OPENED.

2. WIRE COLOR.

BN WH

BK BL YL

PK RD GN

COLOR

BROWN WHITE BLACK BLUE YELLOW PINK RED GREEN

SYMBOL

4-4

CIRCUIT DESCRIPTION

FUSE

H.V.

TRANS-

FORMER

RELAY 2

MICOM CONTROLLER

SECONDARY SWITCH

PRIMARY

SWITCH

MONITOR

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.

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.

H.V.

TRANS-

FORME

SECONDARY SWITCH

FUSE

PRIMARY

SWITCH

RELAY 2

MONITOR

SWITCH

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

• The air is also directed into the oven to exhaust the vapor in the oven through the upper plate.

• Cooking time starts counting down.

• 3.15 volts AC is generated from the filament winding of the high voltage transformer. This 3.15 volts is applied to the magnetron to heat the magnetron filament through two noise-preventing choke coils.

• A high voltage of approximately 2,210 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.

MICOM CONTROLLER

WHEN TOUCHING THE START KEY WITH THE CONVECTION COOKING.

• The contacts of the primary switch and the secondary switch close the circuit.

• Damper close.

• Turntable rotates.

• Fan Motor, Circulation Motor rotate.

RELAY 4

G-Y

4-5

CONVECTION

HEATER

SERVICE INFORMATION

TOOLS AND MEASURING INSTRUMENTS

NECESSARY TOOLS

Tools normally used for TV servicing are sufficient. Tools needed for service are listed below.

• Diagonal pliers

• Long nose pliers

• Phillips screwdriver

• Flat blade screwdriver

• Wrench (size 2 inches(5mm))

• Nutdriver (size 2 inches(5mm))

• Adjustable wrench

• Soldering iron

• Solder

• Vinyl insulation tape

• Polishing cloth

MICROWAVE LEAKAGE TEST

CAUTIONS

• Be sure to check microwave leakage prior to servicing the oven if the oven is operative prior to servicing.

• The service personnel should inform the manufacture importer, or assembler of any certified oven unit found to have a microwave emission level in excess of 5 mW/cm2and 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.

• If the oven operates with the door open, the service personnel should:

- Tell the user not to operate the oven.

- Contact the manufacturer.

• The service personnel should check all surface and vent openings for microwave leakage.

• Check for microwave leakage after every servicing. The power density of the microwave radiation leakage emitted by the microwave oven should not exceed 5 mW/cm2. Always start measuring of an unknown field to assure safety for operating personnel from radiation leakage.

NECESSARY MEASURING INSTRUMENTS

• TESTER (VOLTS-DC, AC, Ohm meter)

• Microwave survey meter

- Holaday HI-1500 HI-1501

- Narda 8100

8200

• Inch scale

• 600 cups (cc) non conductive material beaker (glass or plastic), inside diameter: approx. 31/2inches (8.5 cm)

• Cylindrical and made of borosilicate glass vessel. max. thickness: 0.12 inches (3mm) outside diameter: approx. 7.5 inches (190mm) height: approx. 3.5 inches (90mm)

• Glass thermometer: 212°F (100°C) (1 deg scale)

MEASURING MICROWAVE ENERGY LEAKAGE

• Pour 275±15cc of 20±5°C(68±9°F) water in a beaker which is graduated to 600 cc, and place the beaker on the center of the turntable.

• Set the energy leakage monitor to 2,450 MHz and use it following the manufacturer's recommended test procedure to assure correct result.

• When measuring the leakage, always use the 2 inches (5cm) spacer supplied with the probe.

• Operate the oven at its maximum output.

• Measure the microwave radiation using and electromagnetic radiation monitor by holding the probe perpendicular to the surface being measured

Move probe along shaded area

Probe scanning speed Less than 2.5 cm/sec (1 in/sec)

5-1

+ 27 hidden pages

Kenmore 721.67903, 721.67902, 721.67909 Service Manual

Specifications and Main Features

Frequently Asked Questions

User Manual