KitchenAid KHMS105E User manual

LIT4317216Printed in U.S.A.
SERVICE MANUAL
for the
March, 1997
MICROWAVE OVEN
HOOD COMBINATION
( E Model Line)

ii
THIS MANUAL CONTAINS INFORMATION NECES-
SARY FOR SERVICING THE KITCHENAID MICRO-
WAVE OVEN HOOD COMBINATION , MODELS:
KHMS105E
KHMC107E
THE MANUAL IS DESIGNED TO BE USED ONLY BY
QUALIFIED SERVICE PERSONNEL. THE SERVICE
INFORMATION IS ORGANIZED TO HELP YOU EAS-
ILY FIND WHAT YOU NEED.
CHECK YOUR LOCAL BUILDING CODE FOR THE
PROPER MODE OF INSTALLATION. IN THE AB-
SENCE OF LOCAL CODES, THIS UNIT SHOULD BE
INSTALLED IN ACCORDANCE WITH THE NATIONAL
ELECTRICAL CODE, ANSI/NFPA NO. 70 - 1990, OR
LATEST EDITION, OR C22.1 CANADIAN ELECTRI-
CAL CODE, PART 1 .

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Microwave Oven Hood Combo Service Manual — LIT 4317216
TABLE OF CONTENTS Page
Important Safety Information .............................................................................................................. v
Theory Of Operation .........................................................................................................................1-1
Component Access ...........................................................................................................................2-1
Component Sections ...................................................................................................................2-1
General ............................................................................................................................................... 2-2
Removing The Microwave Oven & Cabinet .............................................................................2-2
The Protection Control System ....................................................................................................... 2-4
Removing The Oven Door ..........................................................................................................2-4
Removing The Door Choke ........................................................................................................2-5
Removing The Control Panel .....................................................................................................2-6
Removing The Line Fuse ...........................................................................................................2-7
Removing/Adjusting The Interlock Switches ...........................................................................2-8
Removing The Base Thermal Fuse ....................................................................................... 2-11
Removing The Magnetron Thermal Fuse.............................................................................. 2-12
Removing The Cavity Thermal Fuse ..................................................................................... 2-13
Removing The Convection Thermistor .................................................................................. 2-14
The Operating Control System ..................................................................................................... 2-16
Removing The Oven Light Socket ......................................................................................... 2-16
Removing The Control Circuit Board ..................................................................................... 2-17
Removing The Temperature Probe Socket .......................................................................... 2-18
Removing The Fan Motor ........................................................................................................ 2-19
Removing The Power Cord ..................................................................................................... 2-20
Removing The Blower Motor Capacitor ................................................................................ 2-21
Removing The Convection Heating Element........................................................................ 2-22
Removing The Gas Sensor ..................................................................................................... 2-24
Removing The Synchronous Motor........................................................................................ 2-25
Removing A Cooktop Light Socket ........................................................................................ 2-26
The High Voltage Components .................................................................................................... 2-27
Accessing The High Voltage Components ........................................................................... 2-28
Removing The Magnetron ....................................................................................................... 2-29
Removing The High Voltage Rectifier And The High Voltage Capacitor ......................... 2-30
Removing The High Voltage Transformer ............................................................................ 2-32

iv
Page
Component Description & Testing ..................................................................................................3-1
Important Safety Instructions.....................................................................................................3-1
The Thermal Fuses .....................................................................................................................3-4
The Blower Motor Capacitor ......................................................................................................3-5
The Gas Sensor ...........................................................................................................................3-6
The Convection Thermistor........................................................................................................3-7
The Convection Heating Element .............................................................................................3-8
Motors ...........................................................................................................................................3-9
Programming Checks............................................................................................................... 3-10
Things To Know ........................................................................................................................ 3-11
Charts ......................................................................................................................................... 3-12
Checking The Microwave Power Output ............................................................................... 3-15
Checking For Microwave Energy Leakage ........................................................................... 3-16
Component Testing .................................................................................................................. 3-19
Control Circuit Board Checklist .............................................................................................. 3-24
Primary, Monitor, & Secondary Switch Checkout Procedure............................................. 3-25
Tech Tips ............................................................................................................................................4-1
Wiring Diagrams ..........................................................................................................................4-1
Strip Circuits.................................................................................................................................4-3
Specifications ...............................................................................................................................4-7
Specification Charts ....................................................................................................................4-8
Model & Serial Number Explanation...................................................................................... 4-12
KitchenAid Microwave Hood Warranty .................................................................................. 4-13

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Microwave Oven Hood Combo Service Manual — LIT 4317216
IMPORTANT SAFETY INFORMATION
KITCHENAID ASSUMES NO RESPONSIBILITY
FOR ANY REPAIRS MADE ON OUR PRODUCTS
BY ANYONE OTHER THAN AUTHORIZED
KITCHENAID SERVICE TECHNICIANS.
Fire Hazard
Do not obstruct the flow of ventilation air.
Electrical Shock Hazard
It is the customer’s responsibility to:
• Contact a qualified electrical installer.
• Assure that electrical installation is ad-
equate and in conformance with the Na-
tional Electrical Code, ANSl/NFPA 70—
latest edition*, and all local codes and
ordinances.
Failure to do so could result in fire, electrical
shock, or other personal injury.
Take special care when drilling holes into
the wall for venting or electrical wiring. Elec-
trical wires may be concealed behind the
wall covering.
Failure to do so could result In fire, electri-
cal shock, or other personal injury.
WARNING
• National Fire Protection Association
Batterymarch Park
Quincy, Massachusetts 02269
This service manual is intended for factory-
service technicians only. We recommend that
customers DO NOT service their own units,
because of the complexity and risk of high-
voltage electrical shock.
The following information is used throughout
this manual, and should be read carefully.
NOTE
Helpful information that explains a more
complicated step, prior to carrying it out.
Information that will help you avoid actions
that could cause product damage (scratches,
dents, etc.) and damage to personal prop-
erty.
CAUTION
Information that alerts you to potentially
dangerous conditions. These conditions can
cause serious personal injury (burns, fire
and electrical shock, etc.) if the suggested
procedures are not observed.
WARNING

vi
CAUTION
WARNING TO SERVICE TECHNICIANS
• Proper operation of the microwave ovens
requires that the magnetron be properly
assembled to the waveguide and cavity.
Never operate the magnetron unless it is
properly installed.
• Be sure the “RF” seal is not damaged, and
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 the test
procedures and safety information contained
in this manual.
To avoid possible exposure to microwave ra-
diation or energy, visually check the oven for
damage to the door and door seal before
operating the oven. Use your microwave sur-
vey meter to check the amount of leakage
before servicing. In the event that the R.F.
Ieakage exceeds 4 mw/cm2at 5 cm, appropri-
ate 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. Un-
der no circumstances should you try to oper-
ate the oven with the door open.
PRECAUTIONS TO BE OBSERVED BEFORE AND DUR-
ING SERVICING TO AVOID POSSIBLE EXPOSURE TO
EXCESSIVE MICROWAVE ENERGY.
1. Do not operate or allow the oven to be
operated with the door open.
2. Make the following safety checks on all
ovens to be serviced before activating the
magnetron or other microwave source,
and make repairs as necessary:
a)Interlock Operation.
b)Proper Door Closing.
c) Seal and Sealing Surfaces (Arcing,
Wear, and Other Damage).
d)Damage to or Loosening of Hinges and
Latches.
e)Evidence of Dropping or Abuse.
3. Before turning on microwave power for
any service test or inspection within the
microwave generating compartments,
check the magnetron, wave guide or trans-
mission line, and cavity for proper align-
ment, integrity, and connections.
4. 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.
5. A microwave leakage check to verify com-
pliance with the Federal performance
standard should be performed on each
oven prior to release to the owner.
6. Do not attempt to operate the oven if the
door glass is broken.

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Microwave Oven Hood Combo Service Manual —LIT 4317216
CAUTION: BEFORE TOUCHING
ANY OVEN COMPONENTS OR
WIRING, ALWAYS UNPLUG THE
OVEN FROM ITS POWER
SOURCE AND DISCHARGE THE
CAPACITOR BY USING A
20,000-OHM DISCHARGE RESIS-
TOR.
OR
USE AN INSULATED PLASTIC-
HANDLE SCREWDRIVER AND
SHORT ACROSS THE CAPACI-
TOR TERMINALS.
CAUTION
CAUTION: REPLACE BLOWN
FUSE WITH 15 AMPERE CLASS H
FUSE ONLY.
Before replacing the blown oven fuse, test the
upper and lower door interlock switches, cook
relay or latch relay, and interlock monitor switch
(middle switch) for proper operation as de-
scribed in the component test procedures.
DO NOT ATTEMPT TO REPAIR STICKING
CONTACTS OF ANY INTERLOCK SWITCH,
SAFETY SWITCH, OR COOK (LATCH) RE-
LAY (REPLACE SWITCHES).
Any indication of sticking contacts during com-
ponent test requires replacement of that com-
ponent to assure reliability of the safety inter-
lock system.
IF THE FUSE IS BLOWN, THE MONITOR,
PRIMARY INTERLOCK AND SECONDARY
INTERLOCK SWITCHES MUST ALSO BE
REPLACED. BE SURE THEY ARE PROP-
ERLY CONNECTED.
NOTES:
• For proper repair and assembly of the oven
door, refer to page 2-4.
• Interlock switches are not adjustable indi-
vidually.
• For proper repair and adjustment of the
interlock switches, refer to page 2-8.
WARNING
DISCONNECT FROM POWER SUPPLY
BEFORE SERVICING.
CAUTION: HIGH VOLTAGES ARE
PRESENT DURING THE COOK
CYCLE. EXTREME CAUTION
SHOULD BE OBSERVED AT ALL
TIMES.
CAUTION: DO NOT TOUCH
OVEN COMPONENTS OR WIR-
ING DURING OVEN OPERATION.
ATTACH METER LEADS WITH
ALLIGATOR CLIPS WHEN MAK-
ING OPERATIONAL TESTS.
CAUTION: IT IS NEITHER NEC-
ESSARY NOR ADVISABLE TO
ATTEMPT MEASUREMENT OF
HIGH VOLTAGES.
KitchenAid microwave ovens have a monitor-
ing system designed to assure proper opera-
tion of the safety interlock systems.
The interlock monitor switch will immediately
cause the oven fuse to blow if the door is
opened while the following combined failure
exists:
Primary door interlock switch and/or second-
ary interlock switch contacts failed in a closed
position.

viii
R.F. LEAKAGE TEST
When checking for R.F. Ieakage, use an ap-
proved R.F. measuring device to assure less
than 4 mw/cm2emission at 5 cm distance with
a maximum scan rate of 2.5 cm/second, in
compliance with U.S. Government Department
of Health, Education and Welfare 21 CFR1030,
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/cm2to allow for
measurement uncertainty.
NOTE: Enter leakage readings in space BE-
FORE and AFTER on the service document.
All microwave ovens exceeding the emission
level of 4 mw/cm2must 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.
* CDRH: Center for Device and Radiological Health, Food
and Drug Administration.
The interlock monitor switch acts as the final
safety switch protecting the customer from
microwave radiation. If the interlock monitor
switch operated to blow the fuse when the
interlocks failed you must replace all interlock
switches—primary and secondary interlock
switches and the monitor switch with new
ones because the contacts of those interlock
switches may be melted and welded together.
All repairs must be performed in such a man-
ner that microwave energy emissions are mini-
mal.
Address for CDRH is:
Office of Compliance (HFZ-312) Center for
Devices and Radiological Health
1390 Piccard Drive
Rockville, Maryland 20850
CAUTION
EQUIPMENT
• Electromagnetic energy leakage monitor
(NARDA 8100B, HOLADAY H1501).
• 600 ml glass beaker.
• Glass thermometer 100°C or 212°F.
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 250 ML (8.0 oz.) glass of water in
the center of the oven bottom.
3. Select “HIGH” cook power, turn the mi-
crowave oven on, and test for R.F. Ieakage
at the following locations using the pat-
tern shown below:
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.

Microwave Oven Hood Combo Service Manual — LIT 4317216 Page 1-1
1-1
Original 03/97
THEORY OF OPERATION
The microwave oven is powered by the 120-
volt line. Whenever the door is closed and a
cooking function is programmed through the
control panel’s keypad, relay contacts on the
control board close, and complete a circuit
from the L1 side to the neutral side of the line.
The control board uses six relays to operate
the various functions of the microwave oven
(shown below). The relays are controlled by
the microcomputer on the control board, and
perform the functions shown below.
Relay 4 controls the speed of the blower motor
through the control panel. The base thermal
fuse will also turn the blower motor on to its
low speed if the temperature reaches 133˚F.
The schematic configuration for relay 4 is
shown in the following diagram. The relay is
explained in further detail on the following
page.
Relay 1 ........................................................ Oven Light/Fan & Turntable Motors
Relay 2 ........................................................ High Voltage Section
Relay 3 ........................................................ Low-Speed Blower Motor
Relay 4 (N.C. Contacts) ........................... Auto Low-Speed Blower Motor
Relay 4 (N.O. Contacts) ........................... High-Speed Blower Motor
Relay 5 ........................................................ Cooktop Lights
Relay 6 ........................................................ Night Lights
RELAY 4
BASE
THERMAL
FUSE
(LOW)
(HI)
(C)
(C)
(NC) (NO)
BLOWER
MOTOR
L1
1
2
1
CN3
RELAY RY2
MICROCOMPUTER
RELAY RY4
RELAY RY3
RELAY RY1
RELAY RY5
RELAY RY6
CONTROL
CIRCUIT
BOARD

1-2
The normally-closed (N.C.) contacts of relay 4 provide a potential circuit for the Base Thermal
Fuse (see the following strip circuit). If the base of the oven exceeds 133˚F, the thermal fuse
contacts close, and a circuit for the low-speed side of the blower motor is completed, which turns
the motor on. The low-speed blower will operate until the base temperature drops below 104˚F
and opens the thermal fuse contacts, and turns off.
N
L1
15A LINE
FUSE
CAVITY
THERMAL
FUSE
MAGNETRON
THERMAL
FUSE
BK
BK
BK BK
RELAY #4
BASE
THERMAL
FUSE
W
BL
YL
LOW-VOLTAGE
TRANSFORMER
W
BLOWER
MOTOR
LOW
RD
MICROCOMPUTER
BOARD
4 1
7
CAPACITOR
Y
R
When the low-speed fan is selected by the user at the control panel, relay 3 and the normally-
closed (N.C.) contacts of relay 4, complete the circuit to the low-speed windings of the blower
motor and turn it on.
N
L1
15A LINE
FUSE
CAVITY
THERMAL
FUSE
MAGNETRON
THERMAL
FUSE
BK
BK
BK BK
RELAY #4
W
BL
BR
LOW-VOLTAGE
TRANSFORMER
W
BLOWER
MOTOR
LOW
RD
RELAY #3
MICROCOMPUTER
BOARD
4 1
6
CAPACITOR
Y
R
When the high-speed fan is selected by the user at the control panel, the normally-open (N.O.)
contacts of relay 4 complete the circuit to the high-speed windings of the blower motor and turn
it on.
N
L1
15A LINE
FUSE
CAVITY
THERMAL
FUSE
MAGNETRON
THERMAL
FUSE
BK
BK
BK BK
RELAY #4
W
BL
BK
LOW-VOLTAGE
TRANSFORMER
BLOWER
MOTOR
HIGH
RD
MICROCOMPUTER
BOARD
4 1
8
CAPACITOR
Y
R