Electrolux FGMO205KFA User manual

All About
Servicing
MICROWAVE OVENS
With Electronic Controls
™
Publication #5995557609 Part # 316439603 January 2009
Electrolux Major Appliances; North America
250 Bobby Jones Expwy
Augusta, GA 30907

Section 1 Basic Information
1-1
Safe Servicing Practices
Avoid personal injury and/or property damage by observing important Safe Servicing Practices.
Following are some limited examples of safe practices:
1. DO NOT attempt a product repair if you have any doubts as to your ability to complete the repair in a safe and
satisfactory manner.
2. Always Use The Correct Replacement Parts as indicated in the parts documentation. Substitutions may defeat
compliance with Safety Standards Set For Home Appliances. Do not exceed maximum recommended wattage on
light bulb replacements. Doing so could blow fuses and/or damage transformers.
3. Before servicing or moving an appliance:
• Remove power cord from the electrical outlet, trip circuit breaker to the OFF position, or remove fuse.
4. Never interfere with the proper operation of any safety device.
5. Use ONLY REPLACEMENT PARTS CATALOGED FOR THIS APPLIANCE. Substitutions may defeat compliance with
Safety Standards Set For Home Appliances.
6. GROUNDING: The standard color coding for safety ground wires is GREEN, or GREEN with YELLOW STRIPES.
Ground leads are not to be used as current carrying conductors. It is EXTREMELY important that the service
technician reestablish all safety grounds prior to completion of service. Failure to do so will create a hazard.
7. Prior to returning the product to service, ensure that:
• All electrical connections are correct and secure.
• All electrical leads are properly dressed and secured away from sharp edges, high-temperature components,
and moving parts.
• All non-insulated electrical terminals, connectors, heaters, etc. are adequately spaced away from all metal
parts and panels.
• All safety grounds (both internal and external) are correctly and securely connected.
• All panels are properly and securely reassembled.
© 2010 Electrolux Home Products, Inc.

Section 1 Basic Information
1-2
This Manual has been prepared to provide Electrolux Service Personnel with Operation and Service Information for
Electrolux Microwave Ovens FGMO205KFA, FGMO205KBA, FGMO205KWA and FPMO209KFA.
Table of Contents
Section 1 Basic Information
Safe Servicing Practices ........................................ 1-1
Table of Contents................................................. 1-2
Warnings and Safety Information .......................... 1-3
Precautions To Be Observed Before And During
Servicing To Avoid Possible Exposure To
Excessive Microwave Energy ................................. 1-4
Before Servicing................................................... 1-4
Danger High Voltage ............................................ 1-4
Before Servicing................................................... 1-5
When Testing Is Completed .................................. 1-5
Microwave Measurement Procedure USA................ 1-6
Microwave Measurement Procedure Canada........... 1-7
Product Specification ............................................ 1-8
Grounding Instructions ......................................... 1-9
Electrical Requirements ........................................ 1-9
Oven Diagram...................................................... 1-10
Section 2 Operation
Section 2 Operation
Operating Sequence Description............................ 2-1
Off Condition .................................................... 2-1
Cooking Condition ............................................. 2-1
Oven Schematic-Off Condition............................... 2-2
Oven Schematic-Cooking Condition........................ 2-2
Power Level P-0 To P-90 Cooking .......................... 2-3
Sensor Cooking Condition ..................................... 2-3
Cooking Sequence................................................ 2-4
Component Descriptions ....................................... 2-4
Door Open Mechanism ......................................... 2-4
Door Sensing And Primary Interlock Switch ............ 2-4
Monitor Switch ..................................................... 2-4
Turntable Motor ................................................... 2-5
Cooling Fan Motor ................................................ 2-5
Cavity Temperature Fuse ...................................... 2-5
Monitor Fuse........................................................ 2-5
Magnetron Temperature Fuse ............................... 2-5
Humidity Sensor Circuit......................................... 2-6
Section 3 Troubleshooting and Testing
Warnings and Cautions......................................... 3-1
Troubleshooting Guide Chart................................. 3-2
Test Procedures ................................................... 3-3
Section 4 Component Teardown
Warnings and Cautions......................................... 4-1
Outer Case Removal............................................. 4-2
Power Transformer Removal ................................. 4-2
High Voltage Rectifi er And High Voltage
Capacitor Removal ............................................... 4-3
Magnetron Removal ............................................. 4-3
Oven Lamp And Lamp Socket Removal .................. 4-4
Positive Lock® Connector (No-Case Type)
Removal .............................................................. 4-4
Turntable Motor Removal...................................... 4-4
Servicing The Touch Control Panel ....................... 4-5
Control Panel Assembly Removal........................... 4-6
Cooling Fan Motor Removal .................................. 4-7
AH Sensor Removal.............................................. 4-8
Door Sensing Switch, Primary Interlock
Switch And Monitor Switch Removal ...................... 4-8
Door Sensing Switch, Primary Interlock
Switch, And Monitor Switch Adjustment ................. 4-8
Door Replacement................................................ 4-9
Sealer Film .......................................................... 4-10
Section 5 Wire Diagrams
Wiring Schematic Oven OFF Condition ................... 5-1
Wiring Diagram.................................................... 5-2
Section 6 Parts List
Control Panel And Door Parts ................................ 6-1
Oven And Cabinet Parts List.................................. 6-2
Oven And Cabinet Parts Exploded View.................. 6-3
Packing and Accessories Exploded View ................. 6-4

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:
Inverter unit, that includes high voltage capacitor, high voltage power transformer, high voltage
rectifier, heat sink, etc., magnetron, high voltage harness etc.; If provided, fan assembly, cooling fan
motor.
All the parts marked “*” on parts list are used at voltages more than 250v.
Removal of the outer wrapper gives access to voltage above 250v.
All the parts marked “ä” on parts list may cause undue microwave exposure, by themselves, or when
they are damaged, loosened or removed.
Section 1 Basic Information
1-3
WARNING
This service manual is intended for use by persons having electrical and mechanical training and a
level of knowledge of these subjects generally considered acceptable in the appliance repair trade.
Electrolux home products cannot be responsible, nor assume any liability, for injury or damage of
any kind arising from the use of this manual.
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.
WARNING

Section 1 Basic Information
1-4
Precautions To Be Observed Before And During 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 micro
wave 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.
3. 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.
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 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 Measurement
Procedure outlined in this service manual.
If microwave emissions level is in excess of the specified limit, contact ELECTROLUX HOME PRODUCTS, INC.
immediately.
If the unit operates with the door open, service person should:
1. Tell the user not to operate the oven.
2. Contact Electrolux HOME PRODUCTS, INC. and Food and Drug Administration’s Center for Devices and
Radiological Health immediately.
Service personnel should inform ELECTROLUX HOME PRODUCTS, INC. 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 compliance.
Danger 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
of approximately 8KV.
The aluminium heat sink is connected to the switching power transistor collector pole, and has an energized high
voltage potential of approximately 650V peak.
DO NOT ACCESS THE HIGH VOLTAGE TRANSFORMER, HIGH VOLTAGE CAPACITOR, HIGH VOLTAGE DI-
ODE AND HEAT SINK WHEN THE POWER SUPPLY IS CONNECTED TO AN ELECTRICAL OUTLET.

Microwave ovens contain circuitry capable of producing
very high voltage and current. Contact with the
following parts may result in a severe, possibly fatal,
electrical shock.
Inverter unit, that includes High Voltage Capacitor,
High Voltage Power Transformer, High Voltage Rectifier,
Heat sink etc., and Magnetron, High Voltage Harness etc..
Read the Service Manual carefully and follow all
instructions.
WARNING
Section 1 Basic Information
1-5
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.
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 oven power supply cord and then
remove the outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4. Disconnect leads to the primary of the inverter unit.
5. Ensure that these leads remain isolated from other
components and oven chassis by using insulation
tape.
6. After that procedure, reconnect the power supply
cord.
When 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 leads to the primary of the inverter unit.
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 then
set the microwave timer for two (2) minutes. When
the two minutes has elapsed (timer at zero) care-
fully 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.
Don't Touch!
Danger High
Voltage
To discharge the high voltage capacitor, 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.
NOTE
To discharge the high voltage capacitor, 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.
NOTE

Section 1 Basic Information
1-6
Microwave Measurement Procedure (USA)
A. Requirements:
1) Microwave leakage limit (Power density limit): The power density of microwave radiation emitted by a
microwave oven should not exceed 1 mW/cm2at any point 5 cm 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 5 cm or more from the external surface of the oven.
2) Safety interlock switches: Primary interlock switch shall prevent microwave radiation emission in excess of the
requirement as above mentioned, secondary interlock switch shall prevent microwave radiation emission in
excess of 5 mW/cm2at any point 5 cm 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:
Survey instruments that comply with the requirement for instrumentation as prescribed by the performance
standard for microwave ovens, 21 CFR 1030.10(c)(3)(i), must be used for testing.
2) Place the oven tray in the oven cavity.
3) Place the load of 275±15 ml (9.8 oz) of tap water initially at 20°±5°C (68°F) 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 nonconductive 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.
4) Set the cooking control on Full Power Cooking Mode.
5) Close the door 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-door leakage test (microwave measurement)
1) Grasp the probe of the survey instrument and hold it perpendicular to the gap between the door 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 door 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 door pull the door 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
4 mW/cm2, and that the primary interlock switch and secondary interlock switch do turn the oven OFF before
any door movement.
NOTE: After servicing, record data on service invoice and microwave leakage report.

Section 1 Basic Information
1-7
Microwave Measurement Procedure (Canada)
After adjustment of the door switches are completed individually or collectively, switch test and microwave leakage test
must be performed with survey instrument and test result must be confirmed to meet the requirement of the
performance standard for microwave ovens as under mentioned.
A. Requirements:
Every microwave oven shall function in such a manner that when the oven is fully assembled and operating with
its service controls and user controls adjusted to yield the maximum output, the leakage radiation, at all points at
least 5 cm. from the external surface of the oven, does not exceed:
1) 1.0 mW/cm2with the test load of 275 ± 15 ml of water at an initial temperature 20 ±5°C.
2) 5.0 mW/cm2when the outer enclosure is removed with a test load of 275 ± 15 ml of water at an initial
temperature 20±5°C.
3) 5.0 mW/cm2without a test load.
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.
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 oven tray in the oven cavity.
3) Place the load of 275±15 ml (9.8 oz) of tap water initially at 20°±5°C (68°F) in the center of oven cavity.
The water container shall be a low form of a 600 ml (20 oz) beaker with an inside diameter of approx. 8.5 cm
(3-1/2 in.) and made of an electrically nonconductive 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.
4) Set the cooking control on Full Power Cooking Mode.
5) Close the door 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 with enclosure installed:
1) Grasp probe of survey instrument and hold it perpendicular to gap between door and the body of the oven.
2) Move the probe slowly, not faster than 2.5 cm/sec. along the gap, watching for maximum indication on meter.
3) Check for leakage at the door screen, sheet metal seams and other accessible positions where continuity
of the metal has been breached (eg., around the switches, indicator, and vents). While testing for leakage
around door, pull door 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 4 mW/cm2, and that the primary interlock switch and secondary interlock switch do turn the oven
OFF before any door movement.
D. Leakage test without enclosure:
1) Remove the enclosure (cabinet).
2) Grasp the probe of the survey instrument and hold it perpendicular to all mechanical and electric parts of the
oven that is accessible to the user of the oven including, but not limited to, the waveguide, cavity seams,
magnetron gap between the door and the body of the oven.
3) Move probe slowly, not faster than 2.5 cm/sec. along the gap, watching for the maximum indication on meter.
4) Measure carefully at the point of highest leakage and make sure that the highest leakage is under 5 mW/cm2.
CAUTION: Special attention should be given to avoid electrical shock because HIGH VOLTAGE is
generated during this test.
E. No Load test
1) Operate the oven without a load and measure the leakage by the same method as the above test procedure
“ Leakage test with enclosure installed”
2) Make sure that the highest leakage should not exceed 5 mW/cm2.
NOTE: After servicing, record data on service invoice and microwave leakage report.

Section 1 Basic Information
1-8
Product Specification
Item Description
Power Requirements (USA)120 Volts / 14.2 Amperes, 1700 Watts
60 Hertz
Single phase, 3 wire grounded
Power Output 1200 watts (IEC 705 Test Procedure)
Operating frequency of 2450MHz
Case Dimensions (excluding handle) Width 24” Height 13-3/8” Depth 19-1/8”
Cooking Cavity Dimensions Width 17-3/8”
(1.8 Cubic Feet ) Height 10-1/2”
Depth 18-5/8”
Oven Cavity Light Yes
Control Complement Touch Control System
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
Add 30 sec pad, Sensor cooking pads, Number selection pads,
Power Level pad, Timer on/off pad, stop/off pad, Start/enter pad,
User pref pad, Popcorn pad, Chicken nuggets pad, Baked potatoe pad,
Melt soften pad, Snack menu pad, Veggies pad, Sensor reheat pad,
Keep warm pad, Auto reheat pad, Auto defrost pad and Auto cook pad.
Safety Standard UL Listed FCC Authorized
DHHS Rules, CFR, Title 21, Chapter 1, Subchapter J
Canadian Standards Association
Health CANADA, Industry Canada

Section 1 Basic Information
1-9
3-Pronged Plug Grounded
Receptacle Box
Grounding Pin
3-Pronged Receptacle
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, 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.
Electrical Requirements
The oven is equipped with a 3-prong grounding plug.
DO NOT UNDER ANY CIRCUMSTANCES CUT OR
REMOVE THE GROUNDING PIN FROM THE PLUG.
The power supply cord and plug must be connected to a
separate 120 Volt AC, 60 Hz, 15 Amp. or more dedicated
line, using a grounded receptacle. 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 contact 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 an extension cord must be used, it should be a 3-wire,
15 amp. or more cord. Do not drape over a countertop
or table where it can be pulled on by children or tripped
over accidentally.
Improper use of the grounding plug can result in
a risk of electric shock.
WARNING

Section 1 Basic Information
1-10
1. One touch door open button. Push to open door.
2. Microwave oven door with see-through window.
3. Safety door latches. The Microwave Oven will not
operate unless the door is securely closed.
4. Door hinges
5. Door seals and sealing surfaces
6. Turntable motor shaft
7. Removable turntable support
Carefully place the turntable support in the
center of the Microwave Oven floor.
8. Removable turntable
Place the turntable on the turntable support
securely. The turntable will rotate clockwise or
counterclockwise. Only remove for cleaning.
9. Ventilation openings (rear).
10. Microwave oven light. It will light when microwave
oven is operating or door is open.
11. Waveguide cover: DO NOT REMOVE.
12. Auto-Touch control panel
13. Time display: 99 minutes, 99 seconds
14. Serial plate
15. Menu Label
Oven Diagram
173
10
9
8
2
5
4
12
13
14
15
11 6
6
The Popcorn, Sensor Reheat & add 30 sec features
are disabled after three minutes when the oven
is not in use. These features are automatically
enabled when the door is opened and closed or
the STOP/ CLEAR pad is pressed.
NOTE

Section 2 Operation
2-1
The following is a description of component functions
during 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 AC is supplied to the control unit.
(Figure 2-1).
1. The display will show “ENJOY YOUR OVEN PRESS
CLEAR AND PRESS CLOCK”. To set any program or
set the clock, you must first touch the STOP/CLEAR
button. The display will clear, and “ : “ appears.
COOKING CONDITION
Program desired cooking time by touching the NUMBER
pads. Program the power level by touching the POWER
LEVEL pad and then a NUMBER pad. 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 2-2)
RELAY CONNECTED COMPONENTS
RY1 Oven Lamp / Turntable Motor / Fan motor
RY2 Power Transformer
2. 120 volts AC is supplied to the primary winding of
the power transformer and is converted to about
3.3 volts AC output on the filament winding, and
approximately 2370 volts AC 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 channeled through the waveguide into the cavity
feedbox, 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, primary
interlock 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 interlock switch and
secondary interlock relay 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) and primary
interlock switch open their contacts, and the
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 interlock switch and
door sensing switch close, and the 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 monitor fuse, primary
interlock switch, relay (RY1) and secondary interlock
relay (RY2), causing the monitor fuse to blow.
Operating Sequence Description

Section 2 Operation
2-2
Figure 2-1. Oven Off Condition
Figure 2-2. Oven ON (Cooking) Condition

Section 2 Operation
2-3
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 (RY2) 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 (High) (100% Power) 29 sec. 0 sec.
Power 9 (P-90) (Approx. 90%) 26 sec. 3 sec.
Power 8 (P-80) (Approx. 80%) 23 sec. 6 sec.
Power 7 (P-70) (Approx. 70%) 20 sec. 9 sec.
Power 6 (P-60) (Approx. 60%) 17 sec. 12 sec.
Power 5 (P-50) (Approx. 50%) 14 sec. 15 sec.
Power 4 (P-40) (Approx. 40%) 11 sec. 18 sec.
Power 3 (P-30) (Approx. 30%) 8 sec. 21 sec.
Power 2 (P-20) (Approx. 20%) 5 sec. 24 sec.
Power 1 (P-10) (Approx. 10%) 3 sec. 26 sec.
Power 0 (P-0) (0% power) 0 sec. 29 sec.
SENSOR COOKING CONDITION
Using the SENSOR function, the foods are cooked
without figuring 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 food is cooked, water vapor is developed. The
sensor “senses” the vapor and its resistance increases
gradually. When the resistance reaches the value set
according to the menu, supplementary cooking is started.
The time of supplementary cooking is determined by
experiments with each food category and inputted into
the LSI.
The ON/OFF time ratio does not correspond with
the percentage of microwave power, because
approximately 2 seconds are needed for heating of
the magnetron filament.
NOTE
2. Heat Potatoes. Moisture and humidity is emitted
rapidly. You can smell the aroma as it cooks.
3. Sensor detects moisture and humidity and
calculates cooking time and variable power.
An example of how the sensor works:
(BAKED POTATOES)
1. Potatoes at room temperature. Vapor is emitted
very slowly.

Section 2 Operation
2-4
DOOR OPEN MECHANISM
The door is opened by pulling the door handle, refer to
the Figure 2-3.
DOOR SENSING AND PRIMARY INTERLOCK
SWITCH
The primary interlock switch is mounted in the lower
position of the latch hook and the door sensing switch
in the secondary interlock system is mounted in the
upper position of the latch hook. They are activated by
the latch heads on the door. When the door is opened,
the switches interrupt the power to all high voltage
components. A cook cycle cannot take place until the
door is firmly closed thereby activating both interlock
switches. The secondary interlock system consists of
the door sensing switch and 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 monitor fuse, when the contacts of
the secondary interlock relay (RY2) and primary interlock
switch fail to open when the door is opened.
Continued on next page.
Figure 2-3. Door Open Mechanism
Component Descriptions
Door Sensing
Switch
Monitor Switch
Switch Lever
Primary Interlock
Switch
Latch Heads
Door
COOKING SEQUENCE
1. Operate the oven in sensor cooking mode by
referring to the operation manual.
2. The coil of shut-off relays (RY1 and RY3) are
energized, the oven lamp, turntable motor and
cooling fan motor are turned on, but the power
transformer is not turned on.
3. After about 32 seconds, the relay (RY2) is energized.
The power transformer is turned on, microwave
energy is produced and first stage is started.
The 32 seconds is the cooling time required to
remove any vapor from the oven cavity and sensor.
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 food,
turn it or season, etc.
5. When the timer reaches zero, an audible signal
sounds. The shutoff relay (RY1 and RY3) and relay
(RY2) are generalized and the power transformer,
oven lamp, etc. are turned off.
6. Opening the door or touching the STOP CLEAR pad,
the time of day will reappear on the display and the
oven will revert to an OFF condition.
The oven should not be operated on Sensor Cooking
immediately after plugging in the unit. Wait two
minutes before cooking on Sensor Cooking.
NOTE
During this first stage, do not open the door or touch
Clear/Off pad.
NOTE

Section 2 Operation
2-5
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 302°F(150°C)
causing the oven to shut down.
MONITOR FUSE
1. The monitor fuse blows when the contacts (COM-
NO) of the primary interlock relay (RY2) and
secondary 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.
MAGNETRON TEMPERATURE FUSE
The magnetron temperature 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
magnetron temperature fuse remains closed. However,
when abnormally high temperatures are reached within
the magnetron, the temperature fuse will open at 257°F
(125°C) causing the oven to shut down. The magnetron
temperature fuse is not reset at room temperature.
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 (RY2), and primary interlock switch
are in the OFF condition (contacts open) due to their
being normally open contact switches. The contacts
of relay (RY1) are in the ON condition (contacts
close).
2. As the door goes to a closed position, the monitor
switch contacts are first opened and then the door
sensing switch and the primary interlock 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 monitor fuse blows simultaneously with
closing of the monitor switch contacts.
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 surrounding the magnetron and cools the
magnetron. This air is channeled 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.
Before replacing a blown monitor fuse test the
door sensing switch, secondary interlock relay
(RY2), relay (RY1), primary interlock switch and
monitor switch for proper operation. (Refer to
“Test Procedure”).
CAUTION
Monitor fuse and switch are replaced as an assembly.
NOTE
The cavity temperature fuse does not reset.
NOTE

Section 2 Operation
2-6
Humidity Sensor Circuit
1. Structure of Absolute Humidity Sensor:
The absolute humidity sensor includes two
thermistors as shown in the illustration below. One
thermistor is housed in the closed vessel filled with
dry air while another in is the open vessel. Each
sensor is provided with the protective cover made of
metal mesh to be protected from the external
airflow.
2. Operational Principle of Absolute Humidity Sensor:
The figure below shows the basic structure of an
absolute humidity sensor. A bridge circuit is formed
by two thermistors and two resistors (R1 and R2).
The output of the bridge circuit is to be amplified by
the operational amplifier. Each thermistor is
supplied with a current to keep it heated at about
150°C (302°F), the resultant heat is dissipated in the
air and if the two thermistors are placed in different
humidity conditions they show different degrees of
heat conductivity leading to a potential difference
between them, causing an output voltage from the
bridge circuit, the intensity of which is increased as
the absolute humidity of the air increases. Since the
output is very minute, it is amplified by the
operational amplifier.
Figure 2-5. Humidity Sensor Operation
Figure 2-4. Humidity Sensor Diagram
(3) Detector Circuit of Absolute Humidity Sensor Circuit:
This detector circuit is used to detect the output
voltage of the absolute humidity circuit to allow the
LSI to control sensor cooking of the unit. When
the unit is set in sensor cooking mode, 16 seconds
clearing cycle occurs, then the detector circuit starts
to function and the LSI observes the initial voltage
available at its AN1 terminal.
With this voltage given, switches SW1 to SW5 in the
LSI are turned on in such a way as to change the
resistance values in parallel with R98-R102.
Changing the resistance values results in that there
is the same potential at both F-3 terminal of the
absolute humidity sensor and AN0 terminal of the
LSI. The voltage of AN1 terminal will indicate about
-2.5V. This initial balancing is set up about 16
seconds after the unit is put in the Sensor Cooking
mode. As the sensor cooking proceeds, the food is
heated to generate moisture by which the resistance
balance of the bridge circuit is deviated to increase
the voltage available at AN1 terminal of the LSI.
Then the LSI observes that voltage at AN1 terminal
and compares it with its initial value, and when the
comparison rate reaches the preset value (fixed for
each menu to be cooked), the LSI causes the unit to
stop sensor cooking; thereafter, the unit goes in the
next operation automatically.
When the LSI starts to detect the initial voltage at
AN1 terminal 16 seconds after the unit has been put
in the Sensor Cooking mode, if it is not possible to
balance the bridge circuit due to disconnection of
the absolute humidity sensor, ERROR will appear on
the display and the cooking is stopped.
Humidity sensor circuit:

Section 3 Troubleshooting and Testing
3-1
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 then 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.
Troubleshooting Guide
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.
If the oven becomes inoperative because of a blown monitor fuse, check the monitor switch, relay
(RY1) secondary interlock relay (RY2), door sensing switch and primary interlock switch before
replacing the monitor fuse. If the monitor fuse is replaced, the monitor switch must also be replaced.
CAUTION
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. To discharge high voltage capacitor, 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.
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.
WARNING
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. To discharge high voltage capacitor, 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.
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.
WARNING

Section 3 Troubleshooting and Testing
3-2