Kenmore 721. 62622, 721.62624, 721.80494, 721.80499, 721.62629 Service Manual

BASIC SERVICE MANUAL

MODEL

JUNE, 2002

FOR

MICROWAVE HOOD COMBINATION

TECHNICAL FLASH

R

721. 62622

721. 62624

721. 62629

721. 80492

721. 80494

721. 80499

CAUTION

SAFETY PRECAUTIONS

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 UL(CSA) 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.

TABLE OF CONTENTS

(Page)

SAFETY PRECAUTIONS ......................................................................................................... Inside front page

SPECIFICATIONS.......................................................................................................................................... 1-1

CAUTIONS ..................................................................................................................................................... 2-1

INSTALLATIONS............................................................................................................................................ 3-1

OPERATING INSTRUCTIONS....................................................................................................................... 4-1

CONTROL PANEL ................................................................................................................................. 4-1

CONTROL PANEL INSTRUCTIONS ..................................................................................................... 4-2

OVERALL CIRCUIT DIAGRAM...................................................................................................................... 5-1

SCHEMATIC DIAGRAM......................................................................................................................... 5-1

MATRIX CIRCUIT FOR TOUCH KEY BOARD ...................................................................................... 5-2

GENERAL INFORMATION FOR SERVICE ................................................................................................... 6-1

GENERAL PRECAUTIONS IN USE ...................................................................................................... 6-1

TRIAL OPERATION ............................................................................................................................... 6-1

FEATURES AND SPECIFICATIONS FEATURES................................................................................. 6-1

SERVICE INFORMATION ............................................................................................................................. 7-1

PRECAUTIONS AND REPAIR SERVICE TIPS..................................................................................... 7-1

MICROWAVE LEAKAGE TEST ............................................................................................................. 7-2

POWER OUTPUT MEASUREMENT ..................................................................................................... 7-3

DISASSEMBLY INSTRUCTIONS .......................................................................................................... 7-4

INTERLOCK SYSTEM .......................................................................................................................... 7-12

INTERLOCK CONTINUITY TEST.......................................................................................................... 7-14

TEST AND CHECKOUT PROCEDURES AND TROUBLESHOOTING................................................. 7-15

A. TEST PROCEDURES................................................................................................................ 7-15

B. CHECKOUT PROCEDURES..................................................................................................... 7-18

C. TROUBLESHOOTING............................................................................................................... 7-21

EXPLODED VIEW .......................................................................................................................................... 8-1

1-1

Rated Power Consumption

1,500W maximum (Microwave oven+Cook top lamps+Ventilation fan)

Microwave Output

1000W (IEC 60705)

Adjustable 100W through 1000W, 10 steps
Frequency 2,450 MHz ± 50 MHz
Power Supply 120 VAC, 60 Hz
Rated Current 13 Amp. (Microwave oven+Cook top lamps+Ventilation fan)
Magnetron Cooling Forced Air Cooling
Rectification Rectification Voltage Double Half-Wave
Door Sealing Choke System
Safety Devices Magnetron Thermostat:

Open at 90

°

C±5°C
Fuse(20A)
Primary Interlock Switch
Secondary Interlock Switch
Interlock Monitor Switch

Magnetron 2M214-161GP
High Voltage Capacitor Capacitor: 1.0µF, 2.1 KV AC
High Voltage Diode Diode; 350mA, 9.0 KV
Cook top Lamp 125 V, 30 W
Cavity Lamp 125 V, 30 W or 40 W
Timer Digital, up to 99 min. 99 sec. (in each cooking stage)
Tray Tempered Safety Glass

Overall Dimensions 29

15

/16”(W)x167/16”(H)x153/8”(D)

Oven Cavity Size 21

9

/16”(W)x141/8”(H)x83/4”(D)

Effective Capacity of Oven Cavity 1.6 Cu.ft.
Accessories Owner’s Manual & Cooking Guide, Installation Manual,

Exhaust Adapter, Exhaust Damper, Mounting Kit and Two
Filters, Rotating Ring Assembly.

SPECIFICATIONS

2-1

CAUTIONS

• 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

3-1

INSTALLATIONS

PRECAUTIONS ON INSTALLATION

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

single-phase power source with a capacity of 15A
or 20A.

B. Avoid placing the unit in a location where there is

direct heat or splashing water.
C. Install the unit on the mounting plate firmly.
D. Place the unit as far away as possible from TV,

radio, etc. to prevent interference.

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.

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

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.

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.

Plug with Ground

Prong

Properly Polarized
and Grounded
Outlet

CONTROL PANEL

4-1

OPERATING INSTRUCTIONS

1

2

5
6

8

11

12

14

15

17

20

21

3

4

7

10

13

16

19

22

18

9

CONTROL PANEL INSTRUCTIONS

4-2

1. Display. The display includes a clock and indicators to

tell you time of day, cooking time settings, cook powers,
quantities, weights and cooking functions selected.

2. Hold Warm. Touch this pad to keep hot, cooked foods

safely warm in your oven for up to 99 minutes, 99
seconds. Hold Warm can be used by itself, or it can
automatically follow a cooking cycle.

3. Popcorn. Touch this pad to pop one of 3 bag sizes of

popcorn without entering a cook time or power.

4. Pizza. Touch this pad to reheat one or several slices of

pizza without entering a cook time or power.

5. Frozen Entree. Touch this pad to cook a 10 - to 20 -

ounce (284 to 567 g) frozen entree without entering a
cook time or power.

6. Potato. Touch this pad to cook up to 4 potatoes without

entering a cook time or power.

7. Beverage. Touch this pad to heat up to 2 cups (250 ml)

of beverage without entering a cook time or power.

8. Auto Cook. Touch this pad to cook microwavable foods

without entering a cook time or power.

9. Auto Reheat. Touch this pad to reheat microwavable

foods without entering a cook time or power.

10. Clock. Touch this pad to enter the correct time of day.

11. Auto Defrost. Touch this pad followed by number

pads to thaw frozen meat by weight.

12. Express Defrost. Touch this pad to express defrost.

“GROUND BEEF 1.0 LBS TOUCH START” will
appear in the display.

13. Kitchen Timer. Touch this pad to set the kitchen timer.

14. Number Pads. Touch number pads to enter cooking

times, cook powers, quantities, weights, or food
categories.

15. Cook Time. Touch this pad followed by number pads

to set a cooking time.

16. Power. Touch this pad after the cook time has been

set, followed by a Number Pad to set the amount of
microwave energy released to cook the food. The
higher the number, the higher the microwave power or
“cooking speed.”

17. Add minute. Touch this pad to cook for

1 minute at 100% cook power, or to add extra minutes
at the set cook power to your cooking cycle.

18. START. Touch this pad to start a function.

If you open the door after the oven begins to cook,
retouch START.

19. STOP/Clear. Touch this pad to erase an incorrect

command, cancel a program during cooking, or to
clear the Display.

20. Turntable On/Off. Touch this pad to turn off the

turntable. “OFF” will appear in the display.

21. Fan ( ). Touch this pad to turn the fan on or off.

22. Light ( ). Touch this pad to turn the light on high,

night or off.

NOTE: If you try to enter incorrect instructions, you will
not hear any tones. Touch STOP/Clear and re-enter the
instructions.

5-1

SCHEMATIC DIAGRAM

OVERALL CIRCUIT DIAGRAM

5-2

MATRIX CIRCUIT FOR TOUCH KEY BOARD

N.C

Auto

Cook

Popcorn

Cook
Time

50

61

72

83

94

N.C N.CN.C N.CN.C N.C

Reheat

N.C

LIGHT

High/Night/Off

FAN

High/Low/Off

N.C

Express

Defrost

N.C

Clock

STOP

Clear

Frozen

Entree

N.C

Add

Minute

N.C

Auto

Defrost

Potato

Beverage

Pizza

Kitchen

Timer

Power

START

Hold

Warm

Turntable

On/Off

6-1

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 glass turntable 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.

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

and then “0” three times. “1, 0, 0, 0” appears in
the display window.

C. 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.
D. After about 5 minutes, make sure the primary

interlock switch, the secondary interlock switch and

the interlock monitor switch operate properly by

opening and closing the door several times. Touch

the START key each time the door is closed.
E. 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.
F. Confirm the water is hot.
G. Finally, measure the output power according to

“POWER OUTPUT MEASUREMENT” on

page 7-3.

FEATURES AND SPECIFICATIONS
FEATURES

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.

GENERAL INFORMATION FOR SERVICE

PRELIMINARY

A. SINCE NEARLY 2,100 VOLTS EXISTS IN SOME

CIRCUITS OF THIS UNIT REPAIRS SHOULD BE
CARRIED OUT WITH GREAT CARE.

The filament leads of magnetron carry High
Voltage with respect to ground. Extreme caution
must be exercised. Never plug the unit into a
power source to determine which component is
defective in high voltage section.

B. TO AVOID POSSIBLE EXPOSURE TO

MICROWAVE ENERGY LEAKAGE, THE
FOLLOWING PRECAUTIONS MUST BE TAKEN
BEFORE SERVICING.

(1) Before the power is applied:

(a) Make sure the primary interlock switch, the

secondary interlock switch and the interlock
monitor switch operate properly by opening
and closing the door several by opening and
closing the door several times.

(b) Make sure the perforated screen and the

dielectric choke of the door are correctly and
firmly mounted.

(2) After power is applied:

(a) Make sure the interlock switch mechanism

is operating properly by opening and closing
the door.

(b) Check microwave energy leakage must be below

the limit of 5 mW/cm

2

.

(All service adjustments should be made for

minimum microwave energy leakage

readings).

(3) Do not operate the unit until it is completely

repaired, if any of the following conditions exist.

The unit must not be operated.
(a) The door does not close firmly.
(b) The hinge is broken.
(c) The door seal is damaged.
(d) The door is bent or warped, or there is any

other visible damage on the unit that may
cause microwave energy leakage.

NOTE: Always keep the seal clean.
(e) Make sure that there are no defective parts

in the interlock mechanism.

(f) Make sure that there are no detective parts

in the microwave generating and transmission
assembly (especially waveguide).

(4) The following items should be checked after the

unit is repaired:
(a) The interlock monitor switch is connected

correctly and firmly.

(b) The magnetron gasket is properly positioned

and mounted.

(c) The waveguide and the oven cavity are intact.

(no microwave energy leakage)

(d) The door can be properly closed and the

safety switches work properly.

(e) The unit must stop when the door is opened or

the time is up.

The unit must not be operated with any of the above
components removed or by-passed.

7-1

PRECAUTIONS AND REPAIR SERVICE TIPS

SERVICE INFORMATION

7-2

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.

• 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
4 mW/cm2. Always start measuring of an unknown field
to assure safety for operating personnel from radiation
leakage.

EQUIPMENT

• TESTER (VOLTS-DC, AC, Ohmmeter)

• Microwave survey meter

- Holaday HI-1500
HI-1501

- Narda 8100

8200

• 600 cc non conductive material beaker (glass or
plastic), inside diameter: approx. 8.5 cm (3

1

/2 in.)

• Glass thermometer: 100°C or 212°F (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-inch
(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)

MICROWAVE LEAKAGE TEST