KitchenAid KOMS155MBL User manual

TECHNICAL EDUCATION
KAC-36
JOB AID 4317340
OVER-THE-COUNTER
MICROWAVE OVEN
Model KOMS155MBL

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Copyright © 2003, Whirlpool Corporation, Benton Harbor, MI 49022
FORWARD
This KitchenAid Job Aid, “Over-The-Counter Microwave Oven,” (Part No. 3173 0), provides the
technician with information on the installation, operation, and service of the Over-The-Counter
Microwave Oven. It is to be used as a training Job Aid and Service Manual. For specific information
on the model being serviced, refer to the “Use and Care Guide,” or “Wiring Diagram” provided with
the microwave oven.
The Wiring Diagrams used in this Job Aid are typical and should be used for training purposes only.
Always use the Wiring Diagram supplied with the product when servicing the unit.
GOALS AND OBJECTIVES
The goal of this Job Aid is to provide detailed information that will enable the service technician to
properly diagnose malfunctions and repair the KitchenAid Over-The-Counter Microwave Oven.
The objectives of this Job Aid are to:
• Understand and follow proper safety precautions.
• Successfully troubleshoot and diagnose malfunctions.
• Successfully perform necessary repairs.
• Successfully return the microwave to its proper operational status.
WHIRLPOOL CORPORATION assumes no responsibility for any repairs made
on our products by anyone other than Authorized Service Technicians.

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TABLE OF CONTENTS
P ge
GENERAL............................................................................................................................... 1-1
Safety First......................................................................................................................... 1-1
Warning To Service Technicians ....................................................................................... 1-
Precautions To Be Observed Before And During Servicing
To Avoid Possible Exposure To Excessive Microwave Energy ...................................... 1-5
R.F. Leakage Test ............................................................................................................. 1-6
Precautions To Be Observed When Troubleshooting ....................................................... 1-7
KitchenAid Model & Serial Number Designations.............................................................. 1-8
Model & Serial Number Label And Wiring Diagram Locations .......................................... 1-9
Specifications................................................................................................................... 1-10
KitchenAid Microwave Oven Warranty ............................................................................ 1-12
INSTALLATION INFORMATION ........................................................................................... 2-1
Removing The Microwave Oven........................................................................................ 2-1
THEORY OF OPERATION ..................................................................................................... 3-1
Microwave Operating Sequence........................................................................................ 3-1
The Absolute Humidity (AH) Sensor Circuit....................................................................... 3-
COMPONENT ACCESS ......................................................................................................... -1
Component Locations ........................................................................................................ -1
Removing The Cabinet ...................................................................................................... -2
Removing The Control Board ............................................................................................ -3
Removing The Door Interlock Switch Assembly ................................................................ -
Removing The Line Fuse And Oven Lamp........................................................................ -6
Removing An Accent Or Task Lampholder And The Turntable Motor .............................. -7
Removing The Humidity Sensor & Cavity Temperature Fuse ........................................... -8
Removing The Magnetron Temperature Fuse And The Magnetron ................................ -10
Removing The High Voltage Capacitor & Diode, And The Cooling Fan Motor ............... -12
Removing The High Voltage Transformer ....................................................................... -15
Removing The Oven Door Assembly .............................................................................. -16
Removing The Oven Door & Control Panel And The Display Assembly ......................... -18

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COMPONENT TESTING ........................................................................................................ 5-1
Door Switches.................................................................................................................... 5-1
Turntable Motor ................................................................................................................. 5-2
HV Capacitor ..................................................................................................................... 5-2
Humidity Sensor ................................................................................................................ 5-3
Cavity & Magnetron Temperature Fuses ........................................................................... 5-3
Line Fuse ........................................................................................................................... 5-
Cooling Fan Motor ............................................................................................................. 5-
High Voltage Transformer.................................................................................................. 5-5
High Voltage Diode ............................................................................................................ 5-5
Magnetron.......................................................................................................................... 5-6
DIAGNOSIS & TROUBLESHOOTING ................................................................................... 6-1
Troubleshooting ................................................................................................................. 6-1
Touch Control Panel Assembly Test ................................................................................. 6-2
Key Unit Test ..................................................................................................................... 6-3
Relay Test.......................................................................................................................... 6-
Defrost Center Test ........................................................................................................... 6-5
Absolute Humidity (AH) Sensor ......................................................................................... 6-6
WIRING DIAGRAMS .............................................................................................................. 7-1
Schematic Diagram ........................................................................................................... 7-1
Wiring Diagram .................................................................................................................. 7-2
P ge

1-1
GENERAL
Electrical Shock Hazard
Plug into a grounded 3-prong outlet.
Do not re ove ground prong.
Do not use an adapter.
Do not use an extension cord.
Failure to follow these instructions can
result in death, fire, or electrical shock.
Electrical Shock Hazard
Disconnect power before servicing.
Replace all parts and panels before
operating.
Failure to do so can result in death or
electrical shock.
SAFETY FIRST
Your safety and the safety of others is very i portant.
We have provided many important safety messages in this Job Aid and on the appliance. Always
read and obey all safety messages.
This is the safety alert symbol.
This symbol alerts you to hazards that can kill or hurt you and others.
All safety messages will follow the safety alert symbol and either the word
“DA GER” or “WAR I G.” These words mean:
All safety messages will tell you what the potential hazard is, tell you how to reduce the
chance of injury, and tell you what can happen if the instructions are not followed.
You can be killed or seriously injured if you don’t
i ediately follow instructions.
You can be killed or seriously injured if you don’t
follow instructions.
ELECTRICAL POWER SUPPLY &
GROUNDING REQUIREMENTS

1-2
Electrical Shock Hazard
Connect green ground wire to ground
screw.
Failure to do so can result in death or
electrical shock.
Electrical Shock Hazard
I proper use of the grounding plug can
result in a risk of electrical shock.
Before touching any oven component or wir-
ing, always unplug the oven from its power
source and discharge the high voltage capaci-
tor (see page 4-12).
Check that the unit is grounded before trouble-
shooting. Be careful of the high voltage circuits.
Discharge any static charge from your body by
touching ground before handling any part of
the circuitry on the control board. Electrostatic
discharge may damage the control circuit.
Do not touch oven components or wiring during
operation. Attach meter leads with alligator
clips when making operational tests.
For continued protection against radiation
emission, replace only with these types of
switches: Primary (Interlock) Switch: SZM-V16-
FA-63 or VP-533A-OF; Secondary (Interlock)
Switch: SZM-V01-FA-32; Interlock (Monitor)
Switch: SZM-VI6-FA-62 or VP-532A-OF; Oven
Lamp Switch: SZM-V6-FA-31 or VP-331 A-OD.
It is neither necessary nor advisable to attempt
measurement of high voltage.
Attaching the adaptor ground terminal to the
wall receptacle cover screw does not ground
the appliance unless the cover screw is metal
and not insulated and the wall receptacle is
grounded through the house wiring.
The microwave oven must be grounded. In the
event of an electrical short circuit, grounding
reduces the risk of electrical shock by providing
an escape wire for the electrical current. The
microwave oven is equipped with a cord having
a grounding wire with a grounding plug. The
plug must be plugged into an outlet that is
properly installed and grounded.
Consult a qualified electrician or serviceman if
the grounding instructions are not completely
understood, or if doubt exists as to whether the
microwave oven is properly grounded. Do not
use an extension cord. If the power supply cord
is too short, have a qualified electrician or
serviceman install an outlet near the micro-
wave oven.

1-3
ELECTROSTATIC DISCHARGE
(ESD) SENSITIVE ELECTRONICS
ESD problems are present everywhere. ESD
may damage or weaken the electronic control
assembly. The new control assembly may ap-
pear to work well after repair is finished, but
failure may occur at a later date due to ESD
stress.
• Use an antistatic wrist strap. Connect the
wrist strap to a green ground connection
point or unpainted metal in the appliance; or
touch your finger repeatedly to a green ground
connection point or unpainted metal in the
appliance.
• Before removing the part from its package,
touch the antistatic bag to a green ground
connection point or unpainted metal in the
appliance.
• Avoid touching electronic parts or terminal
contacts. Handle the electronic control as-
sembly by the edges only.
• When repackaging the failed electronic con-
trol assembly in an antistatic bag, observe
the above instructions.

1-4
To avoid possible exposure to microwave ra-
diation or energy, visually check the oven for
damage to the door and door seal before
operating any oven. Use a microwave survey
meter to check the amount of leakage before
servicing. In the event the R.F. Ieakage ex-
ceeds 4 mw/cm2 at 5 cm, appropriate repair
must be made before continuing to service the
unit. Check interlock function by operating the
door latch. The oven cook cycle should cut off
before the door can be opened.
The door and latching assembly contains the
radio frequency energy within the oven. The
door is protected by three safety interlock
switches. Do not attempt to defeat them.
Under no circu stances should you try to
operate the oven with the door open.
• Proper operation of microwave ovens re-
quires that the magnetron be properly
assembled to the waveguide and cavity.
ever operate the magnetron unless it is
properly installed.
• Be sure the “RF” seal is not damaged and
is assembled around the magnetron dome
properly when installing the magnetron.
• Routine service safety procedures should
be exercised at all times.
• Untrained personnel should not attempt
service without a thorough review of test
procedures and safety information con-
tained in this Job Aid.
WARNING TO SERVICE TECHNICIANS
KitchenAid microwave ovens have a monitor-
ing system designed to assure proper opera-
tion of the safety interlock systems.
The monitor switch will immediately cause the
oven fuse to blow if the door is opened and the
primary door interlock switch and/or the sec-
ondary interlock switch contacts fail in a closed
position.
CAUTION: Replace a blown fuse with a 20
a pere class H fuse only.
Test the upper and lower door interlock
switches, cook relay, and monitor switch (middle
switch) for proper operation as described in the
component test procedures, before replacing
the blown oven fuse.
Do not atte pt to repair sticking contacts
of any interlock switch, safety switch, or
Cook (Latch) relay. The co ponents ust
be replaced.
Any indication of sticking contacts during com-
ponent tests requires replacement of that com-
ponent to assure reliability of the safety inter-
lock system.
If the fuse is blown, the Monitor switch, and
the Pri ary, and Secondary interlock
switches ust be replaced. Be sure they
are properly connected.

1-5
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 the microwave power
for any service test or inspection within the
microwave generating components, check
the magnetron, wave guide or transmis-
sion 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, using procedures described in
this Job Aid, before the oven is released to
the owner.
E. A microwave leakage check to verify com-
pliance with the Federal Performance Stan-
dard should be performed on each oven
prior to release to the owner.
F. Do not attempt to operate the oven if the
door glass is broken.

1-6
R.F. LEAKAGE TEST
EQUIPMENT
• Electromagnetic energy leakage monitor
( ARDA 8100B, HOLADAY H 1501 ).
• 275 ±15 ML glass beaker.
TEST
On every service call, checks for microwave
energy emission must be made according to
the following manner.
1. Remove the cooking rack from the oven
cavity, if the microwave oven is so
equipped.
2. Place a 275 ±15 ML (9.3 oz.) glass of
water in the center of the oven bottom.
3. Select "HIGH" cook power, turn the micro-
wave oven on, and test for R.F. Ieakage at
the following locations:
a)Around the cabinet at the front.
b)Around the door.
c) Across the console panel.
d)Horizontally across the door.
e)Vertically across the door.
f) Diagonally across the door.
g)Across the air vents.
h)Across the rear air vent.
i) All lockseams.
j) Weld at bottom.
k) Bottom plate.
I) Oven feet.
4. The scan speed is one inch per second.
When checking for R.F. Ieakage, use an ap-
proved R.F. measuring device to assure less
than 4 mw/cm2 emission at 5 cm distance with
a maximum scan rate of 2.54 cm/second, in
compliance with U.S. Government Department
of Health, Education and Welfare 21CFR1030,
Performance Standard for Microwave Ovens.
A properly operating door and seal assembly
will normally register small emissions, but they
must be no greater than 4 mw/cm2 to allow for
measurement uncertainty.
OTE: Enter leakage readings in space BE-
FORE and AFTER on the service document.
All microwave ovens exceeding the emission
level of 4 mw/cm2 must be reported to Dept. of
Service for Microwave Ovens immediately and
the owner should be told not to use the micro-
wave oven until it has been repaired com-
pletely.
If a microwave oven is found to operate with the
door open, report to Dept. of Service, the
manufacturer and CDRH* immediately. Also
tell the owner not to use the oven.
The monitor switch acts as the final safety
switch protecting the customer from micro-
wave radiation. If the monitor switch operated
to blow the fuse when the interlocks failed, you
must replace all interlock switches with new
ones, because the contacts of those interlock
switches may be melted and welded together.
If safety interlock/monitor switch replacement,
or adjustment, is required, you must reconnect
the circuit, and perform a continuity check on
the monitor circuit.
All repairs must be performed in such a manner
that microwave energy emissions are minimal.
Address for CDRH is:
Office of Co pliance (HFZ-312) Center for
Devices and Radiological Health
1390 Piccard Drive
Rockville, MD 20850
* CDRH: Center for Devices and Radiological Health,
Food and Drug Administration.