Sub-Zero WOLF MS24-1100 User manual

General Information 2
Troubleshooting Guide 12
Component Access & Removal 24
Wiring Diagrams 30
subzero.com 800.222.7820
MS24-1100
Service Manual

Page 2
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MS24-1100
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 Federal Performance Standard should be performed
on each oven prior to release to the owner.
BEFORE SERVICING
Before servicing an operative unit, perform a microwave emission check as per the Microwave Measure-
ment Procedure outlined in this service manual.
If microwave emissions level is in excess of the specified limit, contact WOLF immediately @
1-800-332-9513.
If the unit operates with the door open, service person should 1) tell the user not to operate the oven
and 2) contact WOLF and Food and Drug Administration's Center for Devices and Radiological Health
immediately.
Service personnel should inform WOLF of any certified unit found with emissions in excess of 4mW/cm2.
The owner of the unit should be instructed not to use the unit until the oven has been brought into com-
pliance.
DANGER CAUTION
HIGH VOLTAGE
Do not energize a microwave oven with the outer case cabinet removed, because a microwave oven
generates High Voltage in the circuit.
If you intend to operate the oven employing the high frequency switching power converter circuit, you should
take special precautions to avoid an electrical shock hazard.
The high voltage transformer, high voltage capacitor and high voltage diode have energized high voltage
potential approx. 8 KV.
The aluminium heat sink is connected to the switching power transistor Collector pole, and has an energized
high voltage potential approx. 650V peak.
DO NOT ACCESS THE HIGH VOLTAGE TRANSFORMER, HIGH VOLTAGE CAPACITOR, HIGH
VOLTAGE DIODE AND HEAT SINK WHEN THE POWER SUPPLY IS CONNECTED TO AN ELECTRICAL
OUTLET.

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MS24-1100
WARNING TO SERVICE PERSONNEL
Microwave ovens contain circuitry capable of pro-
ducing very high voltage and current, contact with
following parts
may result in a severe, possibly
fatal, electrical shock.
(Example)
High Voltage Capacitor, High Voltage Power
Transformer, Magnetron, High Voltage Rectifier
Assembly, High Voltage Harness etc..
Read the Service Manual carefully and follow all
instructions.
Before Servicing
1. Disconnect the power supply cord , and then
remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
WARNING: RISK OF ELECTRIC SHOCK.
DISCHARGE THE HIGH-VOLTAGE
CAPACITOR BEFORE SERVICING.
The high-voltage capacitor remains charged about 60
seconds after the oven has been switched off. Wait for
60 seconds and then short-circuit the connection of the
high-voltage capacitor (that is the connecting lead of the
high-voltage rectifier) against the chassis with the use of
an insulated screwdriver.
Whenever troubleshooting is performed the power supply
must be disconnected.It may in, some cases, be necessary
to connect the power supply after the outer case has been
removed, in this event,
1. Disconnect the power supply cord, and then remove
outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. Disconnect the leads to the primary of the power
transformer.
5. Ensure that the leads remain isolated from other
components and oven chassis by using insulation
tape.
6. After that procedure, reconnect the power supply cord.
When the testing is completed,
1. Disconnect the power supply cord, and then remove
outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. Reconnect the leads to the primary of the power
transformer.
5. Reinstall the outer case (cabinet).
6. Reconnect the power supply cord after the outer case
is installed.
7. Run the oven and check all functions.
After repairing
1. Reconnect all leads removed from components during
testing.
2. Reinstall the outer case (cabinet).
3. Reconnect the power supply cord after the outer case
is installed.
4. Run the oven and check all functions.
Microwave ovens should not be run empty. To test for the
presence of microwave energy within a cavity, place a cup
of cold water on the oven turntable, close the door and set
the power to HIGH and set the microwave timer for two (2)
minutes. When the two minutes has elapsed (timer at zero)
carefully check that the water is now hot.If the water remains
cold carry out Before Servicing procedure and re-examine
the connections to the component being tested.
When all service work is completed and the oven is fully
assembled, the microwave power output should be checked
and a microwave leakage test should be carried out.

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MS24-1100
MICROWAVE MEASUREMENT PROCEDURE
A. Requirements:
1) Microwave leakage limit (Power density limit): The power density of microwave radiation emitted by a microwave
oven should not exceed 1mW/cm2at any point 5cm or more from the external surface of the oven, measured prior to
acquisition by a purchaser, and thereafter (through the useful life of the oven), 5 mW/cm2at any point 5cm or more
from the external surface of the oven.
2) Safety interlock switches:
Primary interlock relay switch shall prevent microwave radiation emission in excess of the requirement as above
mentioned. Secondary interlock relay and door sensing switch shall prevent microwave radiation emission in excess
of 5 mW/cm2 at any point 5cm or more from the external surface of the oven.
B. Preparation for testing:
Before beginning the actual measurement of leakage, proceed as follows:
1) Make sure that the actual instrument is operating normally as specified in its instruction booklet.
Important:
USA Survey instruments that comply with the requirement for instrumentation as prescribed by the Federal Perform-
ance Standard for microwave ovens, 21 CFR 1030.10(c)(3)(i), must be used for testing.
Canadian Survey instruments that comply with the requirement for instrumentation as prescribed by CSA and NHW
performance standard for microwave ovens must be used for testing recommended instruments are , NARDA 8100
and NARDA 8200.
2) Place the load of 275±15 ml (9.8 oz) of tap water initially at 20±5O C (68OF) in the center of the oven cavity.
The water container shall be a low form of 600 ml (20 oz) beaker with an inside diameter of approx. 8.5 cm (3-1/2
in.) and made of an electrically non conductive material such as glass or plastic.
The placing of this standard load in the oven is important not only to protect the oven, but also to insure that any
leakage is measured accurately.
3) Set the cooking control on Full Power Cooking Mode.
4) Close the drawer and select a cook cycle of several minutes.If the water begins to boil before the survey is completed,
replace it with 275 ml of cool water.
C. Leakage test:
Closed-drawer leakage test (microwave measurement):
1) Grasp the probe of the survey instrument and hold it perpendicular to the gap between the drawer and the body of
the oven.
2) Move the probe slowly, not faster than 1 in./sec. (2.5 cm/sec.) along the gap, watching for the maximum indication
on the meter.
3) Check for leakage at the drawer screen, sheet metal seams and other accessible positions where the continuity of
the metal has been breached (eg., around the switches, indicator, and vents).
While testing for leakage around the drawer, pull the drawer away from the front of the oven as far as is permitted
by the closed latch assembly.
4) Measure carefully at the point of highest leakage and make sure that the highest leakage is no greater than
4mW/cm2, and that the primary interlock switch/secondary interlock relay does turn the oven OFF before any door
movement.
NOTE: After servicing, record data on service invoice and microwave leakage report.

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MS24-1100
SERVICE MANUAL
MICROWAVE OVEN
MS24-1100
FOREWORD
This Manual has been prepared to provide WOLF Service Personnel with
operation and service information for the WOLF microwave.
It is recommended that service personnel carefully study the entire text of
this manual so that they will be qualified to render satisfactory customer
service.
Check the interlock switches and the door seal carefully. Special attention-
should be given to avoid electrical shock and microwave radiation hazard.
WARNING
Never operate the oven until the following points are ensured:
(A) The door is tightly closed.
(B) The door brackets and hinges are not defective.
(C) The door packing is not damaged.
(D) The door is not deformed or warped.
(E) There is no other visible damage with the oven.
Servicing and repair work must be carried out only by trained service
personnel.
DANGER
Certain initial parts are intentionally not grounded and present
a risk of electrical shock only during servicing. Service personnel
-
Do not contact the following parts while the appliance is energized;
HighVoltage Capacitor, PowerTransformer, Magnetron, HighVolt-
age Rectifier Assembly, High Voltage Harness;
If provided, Vent Hood, Fan assembly, Cooling Fan Motor.
All the parts marked “*” on parts list are used at voltages more than 250V.
Removal of the outer wrap gives access to voltage above 250V.
Allthepartsmarked“∆”onpartslistmaycauseunduemicrowaveexpo--
sure,bythemselves,orwhentheyaredamaged,loosened orremoved.
Wolf Appliance, Inc.
P.O. Box 44988
Madison, WI 53744-4988
Customer Care: 800.332.9513

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MS24-1100
ITEM DESCRIPTION
Power Requirements 120 Volts / 13.0 Amperes/1500Watts
60 Hertz
Single phase, 3 wire grounded
Power Output 1100 watts (IEC-705 TEST PROCEDURE)
Operating frequency of 2450MHz
Case Dimensions Width 24"
Height 13-3/8"
Depth 19-1/8"
Cooking Cavity Dimensions Width 17-3/8"
2.0 Cubic Feet Height 10-1/2"
Depth 18-5/8"
Tray Size 15"
Control Complement Touch Control with Touch Glass
Clock ( 1:00 - 12:59 )
Timer (0 - 99 min. 99 seconds)
Microwave Power for Variable Cooking
Repetition Rate;
P-HI .................................................. Full power throughout the cooking time
P-90..................................................................... approx. 90% of Full Power
P-80..................................................................... approx. 80% of Full Power
P-70..................................................................... approx. 70% of Full Power
P-60..................................................................... approx. 60% of Full Power
P-50..................................................................... approx. 50% of Full Power
P-40..................................................................... approx. 40% of Full Power
P-30 .................................................................... approx. 30% of Full Power
P-20..................................................................... approx. 20% of Full Power
P-10..................................................................... approx. 10% of Full Power
P-0..................................................... No power throughout the cooking time
Cavity Light Yes
Safety Standard UL and CUL Listed FCC Authorized
DHHS Rules, CFR, Title 21, Chapter 1, Subchapter J and Canadian Standards
Association. Health CANADA.
SPECIFICATION
GENERAL INFORMATION
GROUNDING INSTRUCTIONS
This oven is equipped with a three prong grounding plug. It must be plugged into a wall receptacle that is properly installed
and grounded in accordance with the National Electrical Code and local codes and ordinances.
In the event of an electrical short circuit, grounding reduces the risk of electric shock by providing an escape wire for the
electric current.
WARNING: Improper use of the grounding plug can result in a risk of electric shock.
Electrical Requirements: The electrical requirements are a 120 volt 60 Hz, AC only, 15 or 20 amp. fused electrical supply.
It is recommended that a separate circuit serving only this appliance be provided. When installing this appliance, observe
all applicable codes and ordinances.
A short power-supply cord is provided to reduce risks of becoming entangled in or tripping over a longer cord.
Where a two-pronged wall-receptacle is encountered, it is the personal responsibility and obligation of the customer to con-
tact a qualified electrician and have it replaced with a properly grounded three-pronged wall receptacle or have a grounding
adapter properly grounded and polarized. If the extension cord must be used, it should be a 3-wire, 15 amp. or higher rated
cord. Do not drape over a countertop or table where it can be pulled on by children or tripped over accidentally.
Popcorn, Beverage, Baked Potatoe, Frozen Entree, Bacon, Frozen
Vegetables, Soften, Reheat, Melt, Auto Defrost, WOLF Gourmet,
manual Defrost, Keep Warm, Settings, Add Minute, Clock, Start/
Quick On, Numbers, Timer, Stop/Clear.
TOUCH CONTROL

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MS24-1100
CAUTION: DO NOT UNDER ANY CIRCUMSTANCES CUT OR
REMOVE THE ROUND GROUNDING PRONG FROM
THIS PLUG.
OVEN DIAGRAM
NOTE:
Some one-touch cooking features such as "EXTRA MINUTE" are disabled
after three minutes when the oven is not used. These features are automati-
cally enabled when the door is opened and closed or the STOP/ CLEAR pad
is pressed.
TOUCH CONTROL
3-Pronged
Plug
Grounded
Receptacle Box
Grounding Pin
3-Pronged Receptacle
One touch
door open pad
Oven door
with see-through
window
Interactive display
Safety door
latches
Rating plate
Door hinges
Door seals and
sealing surfaces
Turntable
Ventilation
openings (rear)
Oven light
Waveguide cover
Touch Glass
Control Panel
Menu label
Turntable support
Power supply cord
Ventilation openings

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MS24-1100
OPERATION
DESCRIPTION OF OPERATING SEQUENCE
The following is a description of component functions dur-
ing oven operation.
OFF CONDITION
Closing the door activates the door sensing switch and
secondary interlock switch. (In this condition, the monitor
switch contacts are opened.)
When oven is plugged in, 120 volts A.C. is supplied to the
control unit. (Figure O-1).
1. The display will show flashing"WELCOME TOUCH
CLEAR AND TOUCH CLOCK TO SET TIME"
To set any program or set the clock, you must first touch
the STOP/CLEAR pad. The display will clear, and " : "
will appear.
COOKING CONDITION
First program the power level by touching the POWER
LEVEL pad then a number pad. (Touch POWER LEVEL
pad twice to choose high.) Then you can enter the cooking
time by touching the number pads.
When the START pad is touched, the following operations
occur:
1. The contacts of relays are closed and components
connected to the relays are turned on as follows.
(For details, refer to Figure O-2)
RELAY CONNECTED COMPONENTS
RY-1 oven lamp/turntable motor/fan motor
RY-2 power transformer
2. 120 volts A.C. is supplied to the primary winding of the
power transformer and is converted to about 3.3 volts
A.C. output on the filament winding, and approximately
2370 volts A.C. on the high voltage winding.
3. The filament winding voltage heats the magnetron
filament and the H.V. winding voltage is sent to a voltage
doubler circuit.
4. The microwave energy produced by the magnetron is
channelled through the waveguide into the cavity feed-
box, and then into the cavity where the food is placed
to be cooked.
5. Upon completion of the cooking time, the power
transformer, oven lamp, etc. are turned off, and the
generation of microwave energy is stopped. The oven
will revert to the OFF condition.
6. When the door is opened during a cook cycle, the
monitor switch, door sensing switch, third door switch,
primary switch relay (RY1) and secondary interlock relay
are activated with the following results. The circuits to
the turntable motor, the cooling fan motor, and the high
voltage components are de-energized, the oven lamp
remains on, and the digital read-out displays the time still
remaining in the cook cycle when the door was opened.
7. The monitor switch electrically monitors the operation of
the primary and third door switch and is mechanically
associated with the door so that it will function in the
following sequence.
(1) When the door opens from the closed position, the
secondary interlock relay (RY2) secondary switch open
their contacts. And contacts of the relay (RY1) remains
closed. Then the monitor switch contacts close.
(2) When the door is closed from the open position, the
monitor switch contacts open first. Then the contacts of
the primary switch, third door switch and door sensing
switch close. And contacts of the relay (RY1) open.
If the primary interlock switch and secondary interlock relay
(RY2) fail with the contacts closed when the door is opened,
the closing of the monitor switch contacts will form a short
circuit through the C/T fuse, primary interlock switch, relay
(RY1) and secondary interlock relay (RY2), causing the
C/T fuse to blow.
POWER LEVEL P-0 TO P-90 COOKING
When Variable Cooking Power is programmed, the 120
volts A.C. is supplied to the power transformer intermittently
through the contacts of relay (RY-2) which is operated by
the control unit within a 32 second time base. Microwave
power operation is as follows:
VARI-MODE ON TIME OFF TIME
Power 10(P-HI) 32 sec. 0 sec.
(100% power)
Power 9(P-90) 30 sec. 2 sec.
(approx. 90% power)
Power 8(P-80) 26 sec. 6 sec.
(approx. 80% power)
Power 7(P-70) 24 sec. 8 sec.
(approx. 70% power)
Power 6(P-60) 22 sec. 10 sec.
(approx. 60% power)
Power 5(P-50) 18 sec. 14 sec.
(approx. 50% power)
Power 4(P-40) 16 sec. 16 sec.
(approx. 40% power)
Power 3(P-30) 12 sec. 20 sec.
(approx. 30% power)
Power 2(P-20) 8 sec. 24 sec.
(approx. 20% power)
Power 1(P-10) 6 sec. 26 sec.
(approx. 10% power)
Power 0(P-0) 0 sec. 32 sec.
(0% power)
Note: The ON/OFF time ratio does not correspond with the
percentage of microwave power, because approx. 2
seconds are needed for heating of the magnetron
filament.

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MS24-1100
SENSOR COOKING CONDITION
Using the SENSOR function, food is cooked without figur-
ing time, power level or quantity. When the oven senses
enough steam from the food, it relays the information to its
microprocessor which will calculate the remaining cooking
time and power level needed for best results. When the food
is cooked, water vapor is developed. the sensor "senses"
the vapor and its resistance increase gradually. When the
resistance reaches the value set according to the menu,
supplementary cooking is started.
The time of supplementary cooking is determined by experi-
ment with each food category and inputted into the LSI. An
example of how sensor works: (Potatoes)
1. Potatoes at room temperature. Vapor is emitted very
slowly.
MICROWAVE
2.Heat Potatoes. Moisture and humidity is emitted very
rapidly. You can smell the aroma as it cooks.
MICROWAVE
AH SENSOR
3.Sensor detects moisture and humidity and calculates
cooking time and variable power.
Cooking Sequence.
1. Touch one of the SENSOR pads (example REHEAT).
NOTE: The oven should not be operated on sensor
immediately after plugging in the unit. Wait two
minutes before cooking on SENSOR.
2. The coil of shut-off relay (RY-1) is energized, the turntable
motor are turned on, but the power transformer is not
turned on.
3. After about 16 seconds, the cook relay (RY-2) is
energized. The power transformer is turned on,
microwave energy is produced and first stage is started.
The 16 seconds is the cooling time required to remove
any vapor from the oven cavity and sensor.
NOTE: During this first stage, do not open the door or touch
STOP/CLEAR pad.
4. When the sensor detects the vapor emitted from the
food, the display switches over to the remaining cooking
time and the timer counts down to zero.
At this time, the door may be opened to stir, turn or
season food.
5. When the timer reaches zero, an audible signal sounds.
The shut-off relay and cook relay are de-energized and
the power transformer, oven lamp, etc. are turned off.
6. Opening the door or touching the STOP/CLEAR pad,
the time of the day will reappear on the display and the
oven will revert to an OFF condition. When the timer
reaches zero, an audible signal sounds.

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MS24-1100
Figure O-1 Oven Schematic - Off Condition
SCHEMATIC
NOTE: CONDITION OF OVEN
1. DOOR CLOSED
2. CLOCK APPEARS ON DISPLAY
SCHEMATIC
3. VARIABLE COOKING CONTROL "HIGH"
2. COOKING TIME PROGRAMMED
1. DOOR CLOSED
NOTE: CONDITION OF OVEN
4. "START" PAD TOUCHED
Figure O-2 Oven Schematic - Cooking Condition
VOLTAGE
HIGH
CAPACITOR
60Hz
BLK
N.C.
COM
COM.N.O.
C/T
FUSE COM
ORG
INTERLOCK
MAGNETRON
HIGH
VOLTAGE
RECTIFIER
MONITOR
SWITCH
GRYYLW
BRN
TRANSFORMER
POWER
B1
SECONDARY
RELAY
N.O.
N
H
F1
F2
F3
COM.
120VAC
GRN
GND
CONTROL UNIT
LAMP
OVEN
WHT
SWITCH
INTERLOCK
PRIMARY
GRY
TABLE
TURN
MOTOR
WHT
FAN
MOTOR
TTM FM
OL
ORG
TEMPCAVITY
FUSE
(RY1)
(RY2)
N.O.
B2
DOOR
SENSING
SWITCH
HUMIDITY
SENSOR
OVEN
RELAY
LAMP
RED
BLK
GRY
WHT
BRN
SWITCH
DOOR
THIRD
COM. N.O.
NOISE FILTER
LC1
C3
C2
GND
WHT
RED
WHT
WHT
BLU
BLK
RED
WHT
WHT
GRY
VOLTAGE
HIGH
CAPACITOR
60Hz
BLK
N.C.
COM
COM.N.O.
C/T
FUSE COM
ORG
INTERLOCK
MAGNETRON
HIGH
VOLTAGE
RECTIFIER
MONITOR
SWITCH
GRYYLW
BRN
TRANSFORMER
POWER
B1
SECONDARY
RELAY
N.O.
N
H
F1
F2
F3
COM.
120VAC
GRN
GND
CONTROL UNIT
LAMP
OVEN
WHT
SWITCH
INTERLOCK
PRIMARY
GRY
TABLE
TURN
MOTOR
WHT
FAN
MOTOR
TTM FM
OL
ORG
TEMPCAVITY
FUSE
(RY1)
(RY2)
N.O.
B2
DOOR
SENSING
SWITCH
HUMIDITY
SENSOR
OVEN
RELAY
LAMP
RED
BLK
GRY
WHT
BRN
SWITCH
DOOR
THIRD
COM. N.O.
NOISE FILTER
LC1
C3
C2
GND
WHT
RED
WHT
WHT
BLU
BLK
RED
WHT
WHT
GRY

Page 11
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MS24-1100
DESCRIPTION AND FUNCTION OF COMPONENTS
DOOR OPEN MECHANISM
The door is opened by pushing the open button on the con-
trol panel, refer to the Figure D-1. When the open button is
pushed, the open button pushes up the switch lever, and
then the switch lever pushes up the latch head. The latch
heads are moved upward and released from latch hook.
Now the door will open.
Figure D-1. Door Open Mechanism
PRIMARY SWITCH,THIRD DOOR SWITCH & DOOR
SENSING SWITCH
The primary switch and third door switch mounted parrallel
to each other horizontally in the lower positions of the latch
hook, the door sensing switch is mounted horizontally in
the upper position of the latch hook. They are activated by
the latch head on the door. When the door is opened, the
switches interrupt the power to all high voltage components,
except the oven lamp . A cook cycle cannot take place un-
til the door is firmly closed thereby activating all interlock
switches. The secondary interlock system consists of the
door sensing switch and the secondary interlock relay located
on the control circuit board.
MONITOR SWITCH
The monitor switch is activated (the contacts opened) by the
latch head on the door while the door is closed. The switch
is intended to render the oven inoperative, by means of
blowing the C/T fuse, when the contacts of the secondary
interlock relay (RY2) and primary interlock switch fail to open
when the door is opened.
Functions:
1. When the door is opened, the monitor switch contact close
(to the ON condition) due to their being normally closed.
At this time the secondary interlock relay, primary switch
and third door switch are in the OFF condition (contacts
open) due to their being normally open contact switches.
2. As the door goes to a closed position, the monitor switch
contacts are first opened and then the door sensing
switch, primary switch and third door switch contacts
close. (On opening the door, each of these switches
operate inversely.)
3. If the door is opened, and the secondary interlock relay
(RY2) and primary interlock switch contacts fail to open,
the C/T fuse blows simultaneously with closing of the
monitor switch contacts.
CAUTION: BEFORE REPLACING A BLOWN C/T FUSE
TEST THE DOOR SENSING SWITCH, SEC-
ONDARY INTERLOCK RELAY (RY2), RELAY
(RY1), PRIMARY/THIRD DOOR INTERLOCK
SWITCH AND MONITOR SWITCH FOR PROP-
ER OPERATION.(REFERTO CHAPTER "TEST
PROCEDURE").
NOTE: C/T FUSE AND MONITOR SWITCH ARE
REPLACED AS AN ASSEMBLY.
TURNTABLE MOTOR
The turntable motor rotates the turntable located on the
bottom of the oven cavity, so that the foods on the turntable
cook evenly during cooking.The turntable may turn in either
direction.
COOLING FAN MOTOR
The cooling fan motor drives a blade which draws external
cool air. This cool air is directed through the air vanes sur-
rounding the magnetron and cools the magnetron. This air
is channelled through the oven cavity to remove steam and
vapors given off from the heating foods. It is then exhausted
through the exhausting air vents at the oven cavity.
MONITOR FUSE
1. The monitor fuse blows when the contacts (COM-NO)
of the primary switch remain closed with the oven door
open and when the monitor switch closes.
2. If the wire harness or electrical components are short-
circuited, this monitor fuse blows to prevent an electric
shock or fire hazard.
CAVITY TEMPERATURE FUSE
The cavity temperature fuse located on the top of the oven
cavity, is designed to prevent damage to the oven by fire. If
the food load is overcooked, by either error in cook time or
defect in the control unit, the cavity temperature fuse will open.
Under normal operation, the cavity temperature fuse remains
closed. However, when abnormally high temperatures are
reached within the oven cavity, the cavity temperature fuse
will open at 302oF(150oC) causing the oven to shut down.
NOTE: This is fuse. It does not reset.
C/T TEMPERATURE FUSE
The C/T fuse located near the magnetron is designed to
prevent damage to the magnetron if an over heated condition
develops in the tube due to cooling fan failure, obstructed
air guide, dirty or blocked air intake, etc.
Under normal operation, the C/T fuse remains closed.
However, when abnormally high temperatures are reached
within the magnetron, the C/T fuse will open at 302OF(150OC)
causing the oven to shut down.
1. The C/T fuse blows when the contacts (COM-NO) of the
secondary interlock relay (RY2) and primary interlock
switch remain closed with the oven door open and when
the monitor switch closes.
2. If the wire harness or electrical components are short-
circuited, this monitor fuse blows to prevent an electric
shock or fire hazard.
NOTE: This is fuse. It does not reset
Door Sensing
Switch
Monitor Switch
Switch Lever Third Door
Switch
Latch Heads
Door
Primary
Switch

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MS24-1100
TROUBLESHOOTING GUIDE
Never touch any part in the circuit with your hand or an uninsulated tool while the power supply is connected.
When troubleshooting the microwave oven, it is helpful to follow the Sequence of Operation in performing the checks. Many
of the possible causes of trouble will require that a specific test be performed. These tests are given a procedure letter
which will be found in the "Test Procedure "section.
MPORTANT: If the oven becomes inoperative because of a blown C/T fuse, check the monitor switch, relay (RY1) sec-
ondary interlock relay (RY2), door sensing switch and primary interlock switch before replacing the C/T
fuse. If the C/T fuse is replaced, the monitor switch must also be replaced. Use part FFS-BA019/KIT as an
assembly.
IMPORTANT: Whenever troubleshooting is performed with the power supply cord disconnected. It may in, some cases,
be necessary to connect the power supply cord after the outer case has been removed, in this event:
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. Disconnect the leads to the primary of the power transformer.
5. Ensure that the leads remain isolated from other components and oven chassis by using insulation tape.
6. After that procedure, reconnect the power supply cord.
When the testing is completed
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. Reconnect the leads to the primary of the power transformer.
5. Reinstall the outer case (cabinet).
6. Reconnect the power supply cord after the outer case is installed.
7. Run the oven and check all functions.

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MS24-1100
Home fuse or circuit breaker blows
when power cord is plugged into
wall receptacle
Monitor fuse blows when power
cord is plugged into wall receptacle.
All letters and indicators do not
appear in display when power cord
is first plugged into wall outlet.
Display does not operate properly
when STOP/CLEAR key is touched.
(Buzzer should sound and":"ortime
of day should appear in display.)
Oven lamp does not light when
door is opened.
Oven lamp does not go out when
door is closed.
Oven lamp lights but fan motor
and turntable motor do not operate.
Oven does not go into cook cycle
when START pad is touched
Oven seems to be operating but
little or no heat is produced in oven
load. (Food incompletely cooked or
not cooked at all at end of cook cycle.)
Oven goes into a cook cycle but
extremely uneven heating is
produced in oven load (food).
Oven does not cook properly when
programmed for Cooking Power 5
mode. (Operates properly on Cook-
ing Power 10 (HIGH) mode.)
Oven goes into COMPU DEFROST-
but food is not defrosted well.
AH sensor does not end during sen-
sor cooking condition. (Oven does
not shut off after a cup of water is
boiling by sensor cooking)
Oven stops at 16 sec. after starting
OFF
CONDITION
PROBLEM
CONDITION
SHORT IN POWER CORD SHORT OR OPENED WIRING MAGNETRON POWER TRANSFORMER H.V. RECTIFIER ASSEMBLY HIGH VOLTAGE CAPACITOR CAVITY TEMPERATURE FUSE C/T FUSE PRIMARY OR DOOR SENSING SWITCH SECONDARY INTERLOCK SYSTEM MONITOR SWITCH MONITOR FUSE OVEN LAMP OR SOCKET COOLING FAN MOTOR TURNTABLE MOTOR TOUCH CONTROL PANEL WRONG OPERATION LOW VOLTAGE DIRTY OVEN CAVITY KEY UNIT RELAY (RY1) AH SENSOR NOISE FILTER
POSSIBLE CAUSE
AND
DEFECTIVE PARTS
TEST PROCEDURE
RE RE A B C D E E F F G H RE RE CK I CK CKCK J K L M N
COOKING
CONDITION
CK = Check / RE = Replace
COOKING
CONDITION
SENSOR

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MS24-1100
A MAGNETRON ASSEMBLY TEST
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
B POWER TRANSFORMER TEST
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. Disconnect the primary input terminals and measure the resistance of the transformer with an
ohmmeter. Check for continuity of the coils with an ohmmeter. On the R x 1 scale, the resistance
of the primary coil should be less than 1 ohm and the resistance of the high voltage coil should be
approximately 90 ohms; the resistance of the filament coil should be less than 1 ohm.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
(HIGH VOLTAGES ARE PRESENT AT THE HIGH VOLTAGE TERMINAL, SO DO NOT ATTEMPT TO
MEASURE THE FILAMENT AND HIGH VOLTAGE.)
4. To test for an open filament, isolate the magnetron from the high voltage circuit. A continuity check
across the magnetron filament leads should indicate less than 1 ohm.
5. To test for a shorted magnetron, connect the ohmmeter leads between the magnetron filament leads
and chassis ground. This test should indicate an infinite resistance. If there is little or no resistance
the magnetron is grounded and must be replaced.
6. Reconnect all leads removed from components during testing.
7. Reinstall the outer case (cabinet).
8. Reconnect the power supply cord after the outer case is installed.
9. Run the oven and check all functions.
MICROWAVE OUTPUT POWER
The following test procedure should be carried out with the microwave oven in a fully assembled condi-
tion (outer case fitted).
HIGH VOLTAGES ARE PRESENT DURING THE COOK CYCLE, SO EXTREME CAUTION SHOULD
BE OBSERVED.
Power output of the magnetron can be measured by performing a water temperature rise test. This
test should only be used if above tests do not indicate a faulty magnetron and there is no defect in the
following components or wiring: silicon rectifier, high voltage capacitor and power transformer. This test
will require a 16 ounce (453cc) measuring cup and an accurate mercury thermometer or thermocouple
type temperature tester. For accurate results, the following procedure must be followed carefully:
1. Fill the measuring cup with 16 oz. (453cc) of tap water and measure the temperature of the water
with a thermometer or thermocouple temperature tester. Stir the thermometer or thermocouple
through the water until the temperature stabilizes. Record the temperature of the water.
2. Place the cup of water in the oven. Operate oven at POWER 10(HIGH) selecting more than 60
seconds cook time. Allow the water to heat for 60 seconds, measuring with a stop watch, second
hand of a watch or the digital read-out countdown.
3. Remove the cup from the oven and again measure the temperature, making sure to stir the
thermometer or thermocouple through the water until the maximum temperature is recorded.
4. Subtract the cold water temperature from the hot water temperature. The normal result should be
38 to 78oF(21 to 42.6oC) rise in temperature. If the water temperatures are accurately measured
and tested for the required time period the test results will indicate if the magnetron tube has low
power output (low rise in water temperature) which would extend cooking time or high power output
(high rise in water temperature) which would reduce cooking time. Because cooking time can be
adjusted to compensate for power output, the magnetron tube assembly should be replaced only if
the water temperature rise test indicates a power output well beyond the normal limits. The test is
only accurate if the power supply line voltage is 120 volts and the oven cavity is clean.

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MS24-1100
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. If the capacitor is open, no high voltage will be available to the magnetron. Disconnect input leads
and check for short or open between the terminals using an ohmmeter.
Checking with a high ohm scale, if the high voltage capacitor is normal, the meter will indicate
continuity for a short time and should indicate an open circuit once the capacitor is charged. If the
above is not the case, check the capacitor with an ohmmeter to see if it is shorted between either
of the terminals and case. If it is shorted, replace the capacitor.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
D HIGH VOLTAGE CAPACITOR TEST
E CAVITY TEMPERATURE FUSE TEST
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. A continuity check across the cavity temperature fuse terminals should indicate a closed circuit
unless the temperature of the cavity temperature fuse reaches approximately 302oF(150oC). An
open cavity temperature fuse indicates overheating of the oven, exchange the cavity temperature
fuse and check inside of oven cavity and for improper setting of cooking time or operation of control
unit. Check for restricted air flow through the vent holes of the oven cavity, especially the cooling
fan and air guide.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
C/T FUSE TEST
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. A continuity check across the C/T fuse terminals should indicate a closed circuit unless the temperature
of the C/T fuse reaches approximately 302OF(150OC). An open C/T fuse indicates overheating of
the magnetron. Check for restricted air flow to the magnetron, especially the cooling fan air guide.
CAUTION: IF THE TEMPERATURE FUSE INDICATES AN OPEN CIRCUIT AT ROOM
TEMPERATURE, REPLACE TEMPERATURE FUSE.
C HIGH VOLTAGE RECTIFIER TEST
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. Isolate the rectifier from the circuit. Using the highest ohm scale of the meter, read the resistance
across the terminals and observe, reverse the leads to the rectifier terminals and observe meter
reading. If a short is indicated in both directions, or if an infinite resistance is read in both directions,
the rectifier is probably defective and should be replaced.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
NOTE: Be sure to use an ohmmeter that will supply a forward bias voltage of more than 6.3 volts.

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MS24-1100
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. Isolate the switch and connect the ohmmeter to the common (COM.) and normally open (NO)
terminal of the switch. The meter should indicate an open circuit with the door open and a closed
circuit with the door closed. If improper operation is indicated, replace the third door interlock switch.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
SECONDARY INTERLOCK SYSTEM TEST
DOOR SENSING SWITCH
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. Isolate the switch and connect the ohmmeter to the common (COM.) and normally open (NO)
terminal of the switch. The meter should indicate an open circuit with the door open and a closed
circuit with the door closed. If improper operation is indicated, replace the door sensing switch.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
NOTE: If the door sensing switch contacts fail in the open position and the door is closed, the cooling
fan, turntable and oven light will be activated by RY1.
SECONDARY INTERLOCK RELAY (RY2)
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. Disconnect two (2) wire leads from the male tab terminals of the Secondary Interlock Relay. Check
the state of the relay contacts using a ohmmeter. The relay contacts should be open. If the relay
contacts are closed, replace the circuit board entirely or the relay itself.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
F PRIMARY AND THIRD DOOR SWITCH TEST
G MONITOR SWITCH TEST
5. If the C/T fuse is blown when the door is opened, check the secondary interlock relay, primary
interlock switch and monitor switch according to the "TEST PROCEDURE" for those switches before
replacing the blown monitor fuse.
CAUTION: BEFORE REPLACING A BLOWN C/T FUSE,TESTTHE SECONDARY INTERLOCK RELAY,
PRIMARY INTERLOCK SWITCH, DOOR SENSING SWITCH AND MONITOR SWITCH
FOR PROPER OPERATION.
If the C/T fuse is blown by improper switch operation, the C/T fuse and monitor switch must be
replaced with "C/T fuse and monitor switch assembly" part number FFS-BA019/KIT, even if the
monitor switch operates normally. The C/T fuse and monitor switch assembly is comprised of a 20
ampere fuse and switch.
6. Reconnect all leads removed from components during testing.
7. Reinstall the outer case (cabinet).
8. Reconnect the power supply cord after the outer case is installed.
9. Run the oven and check all functions.

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MS24-1100
H BLOWN MONITOR FUSE TEST
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. If the monitor fuse is blown when the door is opened, check the primary switch and monitor switch
according to the "TEST PROCEDURE" for those switches before replacing the blown monitor fuse.
CAUTION: BEFORE REPLACING A BLOWN MONITOR FUSE, TEST THE PRIMARY SWITCH AND
MONITOR SWITCH FOR PROPER OPERATION.
If the monitor fuse is blown by improper switch operation, the monitor fuse and monitor switch must
be replaced with "monitor fuse and monitor switch assembly" part number FFS-BA016/KIT, even if
the monitor switch operates normally. The monitor fuse and monitor switch assembly is comprised
of a 20 ampere fuse and switch.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
1. Key Unit.
Please note that key unit is projected capacitive touch technology. Touching the keyglass
surface changes a key pad sensor's local electric field to activate a key action. The amount
of finger flesh's needed to trigger key activation is ~10mm diameter surface contact to the
glass surface. You should not press hard to active a key; only a light touch is needed to
change the pad's local electric field.
a) Run the oven and check all functions.
The following symptoms indicate a defective key unit.
b) When lightly touching a fingertip to any pad and one or more keys do not respond.
c) When lightly touching a fingertip to any pad and only nearby keys respond.
d) When any pad only responds when touch with excessive flesh like a large thumb (more than
20mm diameter of surface contact to the glass surface).
2. Control Unit
The following symptoms indicate a defective control unit.
2-1 In connection with pads.
a) when touch any keypad and there is no key response. Check if key cable is unplugged
between control unit and key unit. Check if key cable end is fully seating into the key unit's
connector.
I TOUCH CONTROL/TOUCH GLASS TEST
3. Discharge high voltage capacitor.
4. Before performing this test, make sure that the primary switch is operating properly, according to the
above Switch Test Procedure. Disconnect the wire lead from the monitor switch (COM) terminal. Check
the monitor switch operation by using the ohmmeter as follows. When the door is open, the meter should
indicate a closed circuit. When the monitor switch actuator is pushed by a screw driver through the lower
latch hole on the front plate of the oven cavity with the door opened (in this condition the plunger of the
monitor switch is pushed in), the meter should indicate an open circuit. If improper operation is indicated,
the switch may be defective. After testing the monitor switch, reconnect the wire lead to the monitor switch
(COM) terminal and check the continuity of the monitor circuit.
5. Reconnect all leads removed from
components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord
after the outer case is installed.
8. Run the oven and check all
functions.
Monitor
Switch
Primary Interlock Switch
Screw Driver
Ohmmeter
RED WHT/WHT
Secondary Interlock Switch

Page 18
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MS24-1100
2-2 In connection with indicators
a) At a certain digit, all or some segments do not light up.
b) At a certain digit, brightness is low.
c) Only one indicator does not light.
d) The corresponding segments of all digits do not light up; or they continue to light up.
e) Wrong figure appears.
f) A certain group of indicators do not light up.
g) The figure of all digits flicker.
2-3 Other possible problems caused by defective control unit.
a) Buzzer does not sound or continues to sound.
b) Clock does not operate properly.
c) Cooking is not possible.
3. If the Key unit or the Control unit is defective.
1) Disconnect the power supply cord, and then remove outer case.
2) Open the door and block it open.
3) Discharge high voltage capacitor.
4) Replace the Control unit assembly.
5) Reconnect all leads removed from components during testing.
6) Re-install the outer case (cabinet).
7) Reconnect the power supply cord after the outer case is installed.
8) Run the oven and check all functions.
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST

Page 19
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MS24-1100
COMPU DEFROST TEST
WARNING : The oven should be fully assembled before following procedure.
(1) Place one cup of water in the center of the turntable tray in the oven cavity.
(2) Close the door, touch the Steaks/chops (for 0.5lbs) and two seconds later the compu defrost
starts.
(3) The oven is in Compu Defrost cooking condition.
(4) The oven will operate as follows
1ST STAGE 2ND STAGE
WEIGHT LEVEL TIME LEVEL TIME
0.5lb 70% 30sec. 40% 15sec.
(5) If improper operation is indicated, the control unit is probably defective and should be checked.
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. Disconnect the leads to the primary of the power transformer.
5. Ensure that these leads remain isolated from other components and oven chassis by using insulation
tape.
6. After that procedure, re-connect the power supply cord.
7. Remove the outer case and check voltage between Pin No. 1 of the 2 pin connector (A) and the
common terminal of the relay RY1 on the control unit with an A.C. voltmeter.
The meter should indicate 120 volts, if not check oven circuit.
RY1 and RY2 Relay Test
These relays are operated by D.C. voltage
Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation.
DC. voltage indicated ............. Defective relay.
DC. voltage not indicated ........ Check diode which is connected to the relay coil. If diode is good,
control unit is defective.
RELAY SYMBOL OPERATIONAL VOLTAGE CONNECTED COMPONENTS
RY1 Approx. 24.0V D.C. Oven lamp / Turntable motor / Cooling fan motor
RY2 Approx. 23.0V D.C. Power transformer
8. Disconnect the power supply cord, and then remove outer case.
9. Open the door and block it open.
10. Discharge high voltage capacitor.
11. Reconnect all leads removed from components during testing.
12. Re-install the outer case (cabinet).
13. Reconnect the power supply cord after the outer case is installed.
14. Run the oven and check all functions.
K
J RELAY TEST
1. Disconnect the power supply cord, and then remove outer case.

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MS24-1100
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
Checking the initial sensor cooking condition
Warning: The oven should be fully assembled before following procedure.
1) The oven should be plugged in at least two minutes before sensor cooking.
2) Room temperature should not exceed 95oF(35oC).
3) The unit should not be installed in any area where heat and steam are generated. The unit should
not be installed for example, next to conventional surface unit. Refer to the "INSTALLATION
INSTRUCTIONS" of the operational manual.
(4) Exhaust vents are provided on the back of the unit for proper cooling and air flow in the cavity. To
permit adequate ventilation, be sure to install so as not to block these vents. There should be some
space for air circulation.
(5) Be sure the exterior of the cooking container and the interior of the oven are dry. Wipe off any
moisture with dry cloth or paper towel.
(6) The Sensor works with food at normal storage temperature. For example, chicken pieces would be
at refrigerator temperature and canned soup at room temperature.
(7) Avoid using aerosol sprays or cleaning solvents near the oven while using Sensor settings. The
sensor will detect the vapor given of by the spray and turn off before food is properly cooked.
(8) If the sensor has not detected the vapor of the food, ERROR will apear and the oven will shut off.
Water load cooking test
Warning: The oven should be fully assembled before following procedure.
Make sure the oven the oven has been plugged in at least two minutes before checking sensor cook
operation . the cabinet should be installed and screws tightened.
(1) The oven should be plugged in at least two minutes before sensor cooking
(2) Fill approximately 200 milliliters (7.2 oz) of tap water in 1000 milliliters measuring cup.
(3) Place the container on the center of tray in the oven cavity.
(4) Close the door.
(5) Touch the STOP/CLEAR pad once, clock pad once, power level pad twice, start pad once, "1' pad
once and "3" pad once. Now, the oven is in the sensor cooking condition and "TEST", "SENSOR" and
"COOK" will appear in the display.
(6) The oven will operate for the first 16 seconds, without generating microwave energy.
NOTE: ERROR will appear if the door is opened or STOP/CLEAR pad is touched during the first
stage of sensor cooking.
(7) After approximately 16 seconds, microwave energy is produced.
If ERROR is displayed, replace the AH sensor or check the control unit, refer to explaination below. If
the oven stops after 5 minutes and ERROR is displayed, check the parts except for the AH sensor.
TESTING METHOD FOR AH SENSOR AND /OR CONTROL UNIT
To determine if the sensor is defective, the simplest method is to replace it with a new replacement sen-
sor.
(1) Disconnect the power supply cord, and then remove outer case.
(2) Open the door and block it open.
(3) Discharge high voltage capacitor.
(4)Remove the AH sensor.
(5)Install the new AH sensor.
(6)Reconnect all leads removed from components during testing.
(7)Re-install the outer case (cabinet)
(8) Reconnect the power supply cord after the outer case is installed.
(9)Reconnect the oven to the power supply and check the sensor cook operation as follows:
9-1. Fill approximately 200 milliliters (7.2 oz) of tap water in a 1000 milliliter measuring cup.
9-2. Place the container on the center of tray in the oven cavity.
9-3. Close the door.
9-4.Touch the clock pad once, power level pad twice, start pad once, "1' pad once and "3" pad once.
9-5. The control panel is in automatic sensor operation.
9-6.The display will start to count down the remaining cooking time, and the oven will turn off automatically
after the water is boiling (bubbling).
If new sensor does not operate properly, the problem is with the control unit, and refer to explanation
L AH SENSOR TEST