Electrolux MCC4060E User manual

SOI 12.06 FV 599 37 42-75
SERVICE MANUAL
MICROWAVE OVENS
©ELECTROLUX HOME PRODUCTS
Corso Lino Zanussi,30
Publication No.
I - 33080 PORCIA /PN (ITALY) 599 37 42-75
Tel [phone]
Fax [phone]
SOI
Edition: 12.2006
EN/SERVICE/FV
Microwave Oven
GRILL AND CONVECTION
MICROWAVE OVEN
(Micromat Combi)
MCC4060E
MO940CXE
EMC4090X
ZM40STX
ZM40STN

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TABLE OF CONTENTS
CAUTION, MICROWAVE RADIATION....................................................................................................4
SERVICING / GENERAL INFORMATION ..............................................................................................5
PRODUCT SPECIFICATIONS ................................................................................................................6
APPEARANCE VIEW ..............................................................................................................................7
CONTROL PANEL...................................................................................................................................4
OPERATION SEQUENCE.....................................................................................................................10
FUNCTION OF IMPORTANT COMPONENTS .....................................................................................12
TROUBLESHOOTING GUIDE...............................................................................................................13
TEST PROCEDURES............................................................................................................................14
JOG CONTROL PANEL ASSEMBLY ....................................................................................................22
SERVICING............................................................................................................................................23
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE..................................................24
MICROWAVE MEASUREMENT............................................................................................................30
TEST DATA A GLANCE ........................................................................................................................31
SCHEMATIC DIAGRAMS......................................................................................................................32
PICTORIAL DIAGRAM ..........................................................................................................................33

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CAUTION
CAUTION
MICROWAVE RADIATION
DO NOT BECOME EXPOSED TO RADIATION FROM THE MICROWAVE GENERATOR OR
OTHER PARTS THAT CONDUCT MICROWAVE ENERGY.
GENERAL IMPORTANT INFORMATIONS
This Manual has been prepared to provide Service Engineers with Operation and Service Information.
It is recommended that service engineers carefully study the entire text of this manual, so they will be qualified
to render satisfactory customer service.
WARNING
Note: The parts marked "*" are used at voltage
more than 250V. (Schematic Diagrams).
WARNING
Never operate the oven until the following points are ensured.
(A) The door is tightly closed.
(B) The door and oven hinges are not defective.
(C) The door packing is not damaged.
(D) The door is not deformed or warped.
(E) There is not any other visible damage with the oven.
Servicing and repair work must be carried out only by trained
Service Engineers.
All the parts marked ”*” on schematic diagrams are used at
voltages more than 250V.
Removal of the outer wrap gives access to potentials above
250V.
If the Magnetron or/and the door assembly are damaged,
loosened or removed may cause undue microwave
exposure.

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SERVICING
WARNING TO SERVICE PERSONNEL
Microwave ovens contain circuitry capable of producing very high voltage and current.
Contact with the following parts will result in electrocution
High voltage capacitor, High Voltage transformer, Magnetron, High voltage rectifier assembly, High voltage
wires.
REMEMBER TO CHECK 3D
1) Disconnect the supply.
2) Door opened, and wedged open.
3) Discharge high voltage capacitor.
WARNING AGAINST THE CHARGE OF THE
HIGH VOLTAGE CAPACITOR
The high-voltage capacitor remains charged about
60seconds after the oven has been switched off.
Wait for 60 seconds and then short-circuit the
connection of the high-voltage capacitor (that is, of
the connecting lead of the high-voltage rectifier)
against the chassis with the use of an insulated
screwdriver.
It is recommended that wherever possible fault-
finding is carried out with the supply disconnected. It
may in, some cases, be necessary to connect the
supply after the outer case has been removed, in this
event carry out 3D checks and then disconnect the
leads to the primary of the power transformer. Ensure
that these leads remain isolated from other
components and the oven chassis. (Use insulation
tape if necessary.) When the testing is completed
carry out 3D checks and reconnect the leads to the
primary of the power transformer.
REMEMBER TO CHECK 4R
1) Reconnect all leads removed from components
during testing.
2) Replace the outer case (cabinet).
3) Reconnect the supply.
4) Run the oven. 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 3D checks 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 carried out.
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.
IMPORTANT: If the oven becomes inoperative
because of a blown fuse F1 in the
monitored latch switch - monitor
switch - circuit, check the monitored
latch switch and monitor switch and
before replacing the fuse F1.
GENERAL INFORMATION
WARNING
THIS APPLIANCE MUST BE EARTHED
IMPORTANT
THE WIRES IN THIS MAINS LEAD ARE COLOURED IN ACCORDANCE WITH THE FOLLOWING
CODE:
GREEN-AND-YELLOW : EARTH
BLUE : NEUTRAL
BROWN : LIVE

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PRODUCT SPECIFICATIONS
SPECIFICATION
ITEM DESCRIPTION
Power Requirements 230 Volts / 50 Hertz / Single phase, 3 wire earthed
Microwave cooking 1.5kW Approx. 6.7A
Convection cooking 2.7kW Approx.12A
Grill cooking 2.7kW Approx.12A
Micro and Grill ................... 2.8 kW Approx. 12.7 A
Power Consumption
Dual cooking Micro and Convection ........ 2.8 kW Approx. 12.7 A
Power Output 900W watts nominal of RF microwave energy (measured by way of IEC 60705)
Operating frequency of 2450 MHz
Grill heating element Power
Output
1300 W (650 W x 2)
Convection heating element
Power Output
1450 W
Case Dimensions Width 550mm Height 368mm Depth 537mm
Cooking Cavity Dimensions Width 375mm Height 272mm
Turntable diameter 325mm
Touch Control System
Clock (1.00-12.59 or 0.00-23.59) / Timer (0 - 99 minutes 30 sec.)
Microwave Power for Variable Cooking
Repetition Rate;
100% (HIGH) ....... Full power throughout the cooking time
70% (MEDIUM HIGH) .................... approx. 70% of FULL Power
50% (MEDIUM)............................... approx. 50% of FULL Power
30% (MEDIUM LOW)...................... approx. 30% of FULL Power
10% (LOW) ..................................... approx. 10% of FULL Power
Convection temperature control range
250°C, 230°C, 220°C, 190°C, 180°C, 160°, 130°C, 100°C, and 40°C
Control Complement
1. COOKING indicator
2. START indicator
3. GRILL indicator
4. CONVECTION indicator
5. MICROWAVE indicator
6. INFORMATION indicator
7. INFORMATION button
8. LANGUAGE button
9. COOKING MODE knob
for microwave cooking
10. TIME/WEIGHT knob
rotate the knob to enter to enter
either the cooking/defrosting time
or weight of food..
11. AUTO COOK button
12. COOK FROM FROZEN button
13. AUTO DEFROST button
14. MICROWAVE POWER LEVEL button
15. + START/QUICK button
16. STOP button
17. CONVECTION button
18. CLOCK SETTIN button
19. LESS/MORE button
for microwave cooking with GRILL
for microwave cooking with CONVECTION
for GRILL
for CONVECTION
Net weight Approx. 23 kg

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APPEARANCE VIEW
OVEN
1. Fixing points (4 points)
2. Grill heating element
3. Convection heating element
4. Oven lamp
5. Control panel
6. Shelf runners
7. Waveguide cover
8. Oven cavity
9. Coupling
10. Door seals and sealing surfaces.
11. Door opening handle
12. Air-vent / intake opening
13. Outer cover
14. Power cord
15. Power supply cord support clip.
U.K . BACK VIEW
EUROPEAN BACK VIEW
16. Turntable
17. Turntable support
18. High Rack
19. Low Rack
20. Square shelf
21. Square tray

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CONTROL PANEL
MCC4090E
Digital display and indicators:
1. COOKING indicator
2. START indicator
3. GRILL indicator
4. CONVECTION indicator
5. MICROWAVE indicator
6. INFORMATION indicator
Operating keys:
7. INFORMATION button
8. LANGUAGE button
9. COOKING MODE knob
for microwave cooking
for microwave cooking with GRILL
for microwave cooking with CONVECTION
for GRILL
for CONVECTION
10. TIME/WEIGHT knob
rotate the knob to enter either the cooking/defrosting
time or weight of food.
11. AUTO COOK button
12. COOK FROM FROZEN button
13. AUTO DEFROST button
14. MICROWAVE POWER LEVEL button
15. START/QUICK button
16. STOP button
17. CONVECTION button
18. CLOCK SETTING button
19. LESS/MORE button

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CONTROL PANEL
EMC4090X
Digital display and indicators:
1. COOKING indicator
2. START indicator
3. GRILL indicator
4. CONVECTION indicator
5. MICROWAVE indicator
6. INFORMATION indicator
Operating keys:
7. INFORMATION button
8. LANGUAGE button
9. COOKING MODE knob
for microwave cooking
for microwave cooking with GRILL
for microwave cooking with CONVECTION
for GRILL
for CONVECTION
10. TIME/WEIGHT knob
rotate the knob to enter either the cooking/defrosting
time or weight of food.
11. AUTO COOK button
12. COOK FROM FROZEN button
13. AUTO DEFROST button
14. MICROWAVE POWER LEVEL button
15. START button
16. STOP button
17. CONVECTION button
18. CLOCK SETTING button
19. LESS/MORE button

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CONTROL PANEL
MO040CXE ZM4060STX
ZM4090X ZM4090STN
Digital display and indicators:
1. COOKING indicator
2. START indicator
3. GRILL indicator
4. CONVECTION indicator
5. MICROWAVE indicator
6. INFORMATION indicator
Operating keys:
7. INFORMATION button
8. LANGUAGE button
9. COOKING MODE knob
for microwave cooking
for microwave cooking with GRILL
for microwave cooking with CONVECTION
for GRILL
for CONVECTION
10. TIME/WEIGHT knob
rotate the knob to enter either the cooking/defrosting
time or weight of food.
11. AUTO COOK button
12. COOK FROM FROZEN button
13. AUTO DEFROST button
14. MICROWAVE POWER LEVEL button
15. START button
16. STOP button
17. CONVECTION button
18. CLOCK SETTING button
19. LESS/MORE button

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OPERATION SEQUENCE
OFF CONDITION
Closing the door activates the monitored latch switch and the stop switch.
IMPORTANT
When the oven door is closed, the contacts COM - NC of the monitored switch must be open.
When the microwave oven is plugged in a wall outlet (230V / 50Hz), the line voltage is supplied to the noise
filter. ( Figure O-1 )
1. The control unit is not energized. The display shows nothing (Fig. O-1 (a)).
2. Open the door. The contacts (COM-NC) of the monitored latch switch are closed and the control unit is
energized. Then contacts of relays RY1 and RY5 are closed, and the oven lamp will light and the display will
show "SELECT LANGUAGE" in 5 languages. (Fig. O-1(b)).
NOTE: Once the language is selected using the LANGUAGE key, the display will show "ENERGY
SAVE MODE TO GO OUT OF ENERGY SAVE MODE SET CLOCK" when the oven is plugged in.
3. Close the door. The contacts (COM-NC) of the monitored latch switch are opened and the contacts of relay
RY1 are opened and the oven lamp will be turned off. The display will show " . 0". (Fig. O-1(c)).
NOTE: Energy save mode
1. If the oven has not been used for more than 3 minutes, the contacts of the relay RY5 will be opened and the
control unit will be not energized. Open and close the door, the control unit will resume.
2. If the clock is set, this energy save mode does not work.
3. If the display shows different messages from ENERGY SAVE MODE, the oven may be set in demo mode.
Close the door, see operation manual to cancel demo mode.
MICROWAVE COOKING CONDITION
HIGH COOKING
Enter a desired cooking time by touching the TIME keys and start the oven by touching START key.
Function sequence (Figure O-2)
CONNECTED COMPONENTS RELAY
Oven lamp, Turntable motor RY1
Power transformer RY3
Fan motor RY6
1. The line voltage is supplied to the primary winding of the high voltage transformer. The voltage is converted to
about 3.3 volts A.C. output on the filament winding and high voltage of approximately 2000 volts A.C. on the
secondary winding.
2. The filament winding voltage (3.3 volts) heats the magnetron filament and the high voltage (2000 volts) is sent
to the voltage doubling circuit, where it is doubled to negative voltage of approximately 4000 volts D.C..
3. The 2450 MHz microwave energy produced in the magnetron generates a wavelength of 12.24 cm. This
energy is channelled through the waveguide (transport channel) into the oven cavity, where the food is
placed to be cooked.
4. When the cooking time is up, a single tone is heard and the relays RY1 + RY3 + RY6 go back to their
home position. The circuits to the oven lamp, high voltage transformer, fan motor and turntable motor are cut
off.
5. When the door is opened during a cook cycle, the switches come to the following condition.
CONDITION
SWITCH
CONTACT DURING
COOKING DOOR OPEN (NO COOKING)
COM-NO Closed Opened
Monitored latch switch COM-NC Opened Closed
Stop switch COM-NO Closed Open
COM-NO Closed Opened
Monitor switch COM-NC Opened Closed
The circuits to the high voltage transformer is cut off when the contacts of relay RY2, and the contacts (COM-NO) of
the monitored latch switch SW1 and the monitor switch SW3 are made open. The circuit to the fan motor is cut off
when the relay RY6 is made open.

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OPERATION SEQUENCE
The circuit to the turntable motor is cut off when the contacts (COM-NO) of the monitored latch switch SW1 are
made open. The oven lamp remains on even if the oven door is opened after the cooking cycle has been
interrupted, because the relay RY1 stays closed. Shown in the display is the remaining time.
6. MONITOR SWITCH CIRCUIT
The monitor switch SW3 is mechanically controlled by oven door, and monitors the operation of the
monitored latch switch SW1.
6-1 When the oven door is opened during or after the cycle of a cooking program, the monitored latch switch SW1,
and stop switch SW2 must open their contacts (COM-NO) first. And the contacts (COM-NC) of the monitored
latch switch SW1 are made closed. After that the contacts (COM - NC) of the monitor switch SW3 can be
closed and the contacts (COM-NO) of monitor switch SW3 are made open.
6-2 When the oven door is closed, the contacts (COM - NC) of the monitor switch SW3 must be
opened and the contacts (COM - NO) of monitor switch SW3 must be closed. After that the contacts
(COM - NO) of the monitored latch switch SW1 and stop switch SW2 are made closed. And the contacts
(COM - NC) of the monitored latch switch SW1 are made open .
6-3 When the oven door is opened and the contacts (COM - NO) of the monitored latch switch SW1 remain
closed, the fuse F2 F8A will blow. Because the relay RY1 and monitor switch SW3 are closed and a short
circuit is caused.
HIGH, MEDIUM HIGH, MEDIUM, MEDIUM LOW, LOW COOKING
When the microwave oven is preset for variable cooking power, the line voltage is supplied to the high voltage
transformer intermittently within a 32-second time base through the relay contact which is coupled with the current-
limiting relay RY2 . The following levels of microwave power are given.
32 sec. ON
100% (HIGH) 100%
24 sec. ON
70% (MEDIUM HIGH) Approx. 70%
18 sec. ON
50% (MEDIUM) Approx. 50%
12 sec. ON
30% (MEDIUM LOW) Approx. 30%
6 sec. ON
10% (LOW) Approx. 10%
NOTE: The ON/OFF time ratio does not exactly correspond to the percentage of microwave power, because
approx. 3 seconds are needed for heating up the magnetron filament.
GRILL COOKING CONDITION
TOP GRILL (Figure O-3a)
In this condition the food is cooked by grill heating element energy. Programme the desired cooking time by turing
the "TIME/WEIGHT" knob and the select knob to “GRILL”. When the "START" button is pressed, the following
operations occur:
1. The numbers on the digital read-out start the count down to zero.
2. The oven lamp, cooling fan motor and turntable motor are energized.
3. The relay RY3 is energized and the main supply voltage is applied to the top grill heatig elements.
4. Now the food is cooked by the top grill heating elements.
NOTE: The grill cooking condition will be carried out continuously until the temperature of the oven cavity rise
to 220°C.
CONVECTION COOKING CONDITION (Figure O-4)
PRE-HEATING (by 40°C - 130°C)
Turn select knob to CONVECTION.
Programme the desired convection temperature of 40°C - 130°C by pressing the CONVECTION button. When the
START button is pressed, the following operations occur:
1. The relays RY1, RY6 and RY7 are energized, the oven lamp, turntable motor, fan motor and convection motor
are turned on.
2. The relay RY4 is energized and the main supply voltage is applied to the convection heating element.
3. After the temperature of oven cavity rises to the selected one, the oven will continue to turn the convection
heating element on and off to maintain the temperature for 30 minutes.

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OPERATION SEQUENCE
PRE-HEATING (by 160°C - 250°C)
Turn select knob to CONVECTION
Programme the desired convection temperature of 160°C - 250°C by pressing the CONVECTION button.
When the START button is pressed, the following operations occur:
1. The relays RY1, RY6 and RY7 are energized, the oven lamp, turntable motor, fan motor and convection
motor are turned on.
2. The relay RY4 and RY3 are is energized and the main supply voltage is applied to the convection heating
element and the grill heating elements.
3. After the temperature of oven cavity rises to the selected one, the oven will continue to turn the convection
heating element on and off to maintain the temperature for 30 minutes. And simultaneously the grill
heating element will be operated at 10% power output.
CONVECTION COOKING (by 250°C)
Programme the cooking time by turning the timer vari knob. And then programme the convection temperature of
250°C by pressing the CONVECTION button. When the START button is pressed, the following operations occur:
1. The relays RY1, RY6 and RY7 are energized, the oven lamp, turntable motor, fan motor and convection motor
are turned on.
2. The relay RY4 and RY3 are energized and the main supply voltage is applied to the convection heating
element and the grill heating elements.
3. The oven will continue to turn the convection heating element on and off to maintain the temperature for the
programmed cooking time. And simultaneously the grill heating elements will be operated at 10% power output.
CONVECTION COOKING (by 40°C - 230°C)
Programme the cooking time by turning the timer vari knob. And then programme the desired convection
temperature of 40°C 230°C by pressing the CONVECTION button. When the START button is pressed, the
following operations occur:
1. The relays RY1, RY6 and RY7 are energized, the oven lamp, turntable motor, fan motor and convection motor
are turned on.
2. The relay RY4 is energized and the main supply voltage is applied to the convection heating element.
3. The oven will continue to turn the convection heating element on and off to maintain the temperature for the
programmed cooking time.
DUAL COOKING CONDITION
MICROWAVE AND CONVECTION (Figure O-5a)
Programme the desired cooking time by turning the select knob to MICROWAVE and CONVECTION. Select the
microwave power level by pressing the MICROWAVE POWER LEVEL button. And select the convection
temperature by pressing the CONVECTION button.
NOTE: The 100% microwave power level can not be selected.
When the + 1min / START button is pressed, the following operations occur:
1. The numbers on the digital read-out start the count down to zero.
2. The oven lamp, fan motor, turntable motor and convection motor are energized.
3. The relay RY4 will be energized and the main supply voltage is applied to the convection heating element.
4. The relay RY2 is energized and the microwave energy is generated by magnetron.
5. Now, the food is cooked by microwave and convection energy simultaneously.
MICROWAVE AND TOP GRILL (Figure O-5b)
Programme the desired cooking time by turning the select knob to MICROWAVE and TOP GRILL. Select the
microwave power level by pressing the MICROWAVE POWER LEVEL button. When the START button is pressed,
the following operations occur:
1. The numbers on the digital read-out start the count down to zero.
2. The oven lamp, fan motor and turntable motor are energized.
3. The relay RY3 is energized and the main supply voltage is applied to the top grill heateing elements.
4. The relay RY2 is energized and the microwave energy is generated by magnetron.
5. Now the food is cooked by microwave and grill simultaneously.

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OPERATION SEQUENCE
ON/OFF TIME RATIO
In dual cooking, the magnetron operate within a 48
second time base. The following table is the ON / OFF
time ratio at each power output of the magnetron.
POWER OUTPUT ON TIME OFF TIME
100% 48 sec. 0 sec.
70% 36 sec. 12 sec.
50% 26 sec. 22 sec.
30% 16 sec. 32 sec.
10% 8 sec. 40 sec.
AUTOMATIC COOKING
Automatic cooking functions automatically work out the
correct cooking mode and cooking time and/or cooking
temperature. They will cook according to the special
cooking sequence.
POWER OUTPUT REDUCTION
After the same cooking mode is carried out for more
than the basis cooking time, the power output is
automatically reduced by turning the control relays on
and off intermittently, as shown in the table below. This
is to protect the oven door against temperature rising.
Cooking mode
Basis cooking
time (minutes)
Reduced power
Output (1%)
Time base
(seconds)
Microwave (100%) 20 70 32
Grill 15 70 48
Convection No reduction
40 (Micro.) 50 48Micro. (70%)
+ Grill 15 (Grill) 50 48
15 (Micro.) 50 48Micro. (100%)
+ Grill 15 (Grill) 50 48
40 (Micro.) 50 48
D
U
A
L Micro. (70%)
+ Conv. No reduction
NOTE:
1. If the multiple sequence cooking is carried out in
same mode, the basis cooking time is calculated
from the first.
2. Even if the cooking is stopped by the STOP button
or opening the door, the basis cooking time is
calculated from the first.
3. If the same cooking mode is repeated within 1
and 15 seconds, the basis cooking time is
calculated from the first.
4. If the same menu of Automatic Cooking is repeated
within 1 minute and 15 seconds, the
power output of the microwave or the grill will be
reduced to 70% after 20 minutes when the oven
is started at first.
FAN MOTOR OPERATION (in Grill,
Convection and Dual mode)
When oven is stopped during cooking, or after the
cooking is completed, the fan motor will operate if the
oven cavità temperature is above 120°C, and the fan
motor will stop if the oven cavity temperature is below
105°C.
CONVECTION MOTOR OPERATION
If the temperature of oven cavity is higher than 120°C
after and when operated by 250°C convection cooking,
250°C dual convection cooking or 250°C preheating,
the convection motor will operate for maximum 1
minute until the oven cavity temperature drops below
105°C.

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FUNCTION OF IMPORTANT COMPONENTS
DOOR OPEN MECHANISM
The door can be opened by pulling the door handle.
Figure D-1. Door Open Mechanism
MONITORED LATCH SWITCH SW1
1. When the oven door is closed, the contacts
(COM-NO) of the switch must be closed.
And the contacts (COM-NC) must be opened.
2. When the oven door is opened, the contacts
(COM-NO) of the switch must be opened.
And the contacts (COM-NC) must be closed.
STOP SWITCH SW2
1. When the oven door is closed, the contacts
(COM-NO) of the switch must be closed.
2. When the oven door is opened, the contacts
(COMNO) of switch must be opened.
MONITOR SWITCH SW3
The monitor switch is activated (the contacts
opened) by the lower latch head on the door while
the door is closed.
The switch is intended to render the oven
inoperative by means of blowing the fuse F2 F8A
when the contacts of the monitored latch switch
SW1 fail to open when the door is opened.
Function
1. When the door is opened, the contacts (COM-NC)
of monitor switch SW3 close (to the ON condition)
due to their being normally closed and contacts
(COM-NO) open. At this time the contacts (COM-
NO) of monitored latch switch SW1 is 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 SW3 contacts (COM-NC) are opened and
contacts (COM-NO) closed and then contacts
(COM-NO) of monitored latch switch SW1 and
stop switch SW2 are closed.(On opening the door,
each of these switches operate inversely.)
3. If the door is opened and the monitored latch
switch SW1 contacts (COM-NO) fail to open,
the fuse F2 F8A blows immediately after
closing of the monitor switch SW3 (COM-NC)
contacts.
CAUTION: BEFORE REPLACING A BLOWN FUSE
SWITCH SW3 FOR PROPER
OPERATION. (REFER TO CHAPTER
“TEST PROCEDURE”).
FUSE F1 20A 250V
If the wire harness or electrical components are
shortcircuited, this fuse F1 20A blows to prevent an
electric shock of fire hazard.
FUSE F2 F8A 250V
1. If the wire harness or electrical components are
shortcircuited, this fuse blows to prevent an
electric shock or fire hazard.
2. The fuse also blows when the monitored latch switch
SW1 remains closed with the oven door
open and when the monitor switch SW3 contact
(COM-NC) closes.
3. The fuse also blows when the asymmetric rectifier,
H.V. rectifier,.H.V. wire harness, H.V.
capacitor, magnetron or secondary winding of
high voltage transformer is shorted.
TC TRANSFORMER
T/C transformer converts A.C. line voltage into low
voltage to drive the control unit.
THERMAL CUT-OUT TC1 125°C (MG)
This thermal cut-out protects the magnetron against
overheat. If the temperature goes up higher than 125°C
because the fan motor is interrupted or the ventilation
openings are blocked, the thermal cut-out TC1 will
open and switch off all the electrical parts. The
defective thermal cut-out must be replaced with a new
one.
THERMAL CUT-OUT TC2 170°C (GRILL)
This thermal cut-out protects the oven against the
overheat during grill cooking, convection cooking or
dual cooking. If the temperature rises above 170°C
because the fan motor is interrupted, the air inlet duct
is blocked or the ventilation openings are obstructed,
the thermal cut-out TC2 opens and switches off all the
electrical parts. When the cut-out cools itself down to
the operating temperature of 155°C, the contacts of the
thermal cut-out will close again.
Latch hook
Tab
SW2: Stop switch
SW3: Monitor switch
SW1:Monitored
latch switch
Latch
Heads
Door

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FUNCTION OF IMPORTANT COMPONENTS
THERMAL CUT-OUT TC3 170°C (CONV.)
This thermal cut-out protects the convection motor
against overheating. If the temperature of the thermal
cut-out TC3 rises above 170°C because the convection
fan is interrupted, the ventilation openings are
obstructed or the other abnormal matter occurs, the
thermal cut-out opens and switches off the convection
heating element and the other electrical parts. When
the cut-out cools itself down to the operating
temperature of 155°C, the contacts of the thermal
cut-out will close again.
ASYMMETRIC RECTIFIER
The asymmetric rectifier is solid state device that
prevents current flow in both directions. And it
prevents the temperature rise of the high voltage
transformer by blowing the fuse F2 F8A when the
high voltage rectifier is shorted.
The rated peak reverse voltage of D1 of the
asymmetric rectifier is 6 KV. The rated peak reverse
voltage of D2 of the asymmetric rectifier is 1.7 KV. D1
and D2 of the asymmetric rectifier or high voltage
rectifier are shorted when the each peak reverse
voltage goes beyond the each rated peak reverse
voltage. (The process of the blowing the fuse F2 F8A.)
1. The high voltage rectifier is shorted by some fault
when microwave cooking or dual cooking.
2. The peak reverse voltage of D2 of the rectifier goes
beyond the rated peak reverse voltage 1.7 KV in the
voltage doubler circuit.
3. D2 of the rectifier is shorted.
4. The large electric currents flow through the high
voltage winding of the high voltage transformer.
5. The large electric currents beyond 8A flow through
the primary winding of the high voltage transformer.
6. The fuse F2 F8A blows by the large electric
currents.
7. The power supplying to the high voltage transformer
is cut off.
NOISE FILTER
The noise filter assembly prevents radio frequency
interference that might flow back in the power circuit.
TURNTABLE MOTOR TTM
The turntable motor rotates the turntable.
FAN MOTOR FM
The 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 channelled through the oven cavity to
remove steam and vapours given off from heating food.
It is then exhausted through the exhausting air vents of
the oven cavity.
CONVECTION MOTOR CM
The convection motor drives the convection fan and
provide the heated air.
GRILL HEATING ELEMENT GH
The grill heating elements are provided to brown the
food and are located on the top of the oven cavity.
CONVECTION HEATING ELEMENT CH
The convection heating element situated at the rear of
the oven cavity. It is intended to heat air driven by the
convection fan. The heated air is kept in the oven and
force-circulated and reheated by the convection
heating element.
CONVECTION COOKING SYSTEM
This oven is designed with a hot air heating system
where food is heated by forced circulation of the hot air
produced by the convection heater. The air heated by
the convection heating element is circulated through
the convection passage provided on the outer casing of
the oven cavity by means of the convection fan which
is driven by the convection motor. It is then enters the
inside of the oven through the vent holes provided on
the back side of the oven. Next, the hot air heats the
food on the turntable and leaves the oven cavity
through the vent in the oven cavity rear wall.
In this way, the hot air circulates inside the oven cavity
to raise its temperature and, at the same time, comes
into contact with the food being cooked. When the
temperature inside the oven cavity reaches the
selected temperature, the heating elements are de-
energized. When the temperature inside the oven
cavity drops below the selected temperature, the
heating elements are energized again. In this way, the
inside of the oven cavity is maintained at approximately
the selected temperature. When the convection time
reaches “0”, the heating elements are de-energized
and the convection fan stops operating and the oven
shuts off. At that time if the cavity air temperature has
risen above 120°C, the fan motor remains rotating.
Automatically the fan motor will be shut down at low
temperature (less than 105°C).
HIGH VOLTAGE
RECTIFIER
ASYMMETRIC
RECTIFIER

SOI 12.06 FV 17/43 599 37 42-75
FUNCTION OF IMPORTANT COMPONENTS
Figure D-2. Convection Cooking System
FIRE SENSING FEATURE
The oven will stop its operation when there is a fire in the
oven cavity in microwave cooking condition.
LSI measures the voltage across the temperature
measurement circuit intermittently within 32-seconds time
base since the oven is started in microwave cooking
condition. The oven will stop its operation when the
difference of the voltage is more than 0.39 volts in
microwave cooking condition.
1. Within a 32-seconds base, the thermistor is energized
for 2 seconds. At that time, the voltage across the
temperature measurement circuit is measured.
2. The oven carries out the procedure above again. If the
second voltage is 0.39V higher than first voltage, LSI
judges it is a fire in the oven cavity and stop the oven.
3. When LSI judges it is a fire in the oven cavity, LSI will
switch off the relays to high voltage transformer and
fan motor and LSI stops counting down.
OPEN JUDGE BY THERMISTOR
1. If the temperature of the thermistor does not rise to
more than 40°C after 4 minutes and 15 seconds from
when the oven is started in convection, grill or dual
cooking mode, the oven is turned off.
2. When the thermistor or the wire harness to the
thermistor is opened, the oven is turned off after 4
minutes and 15 seconds because this condition is
same as above.
DAMPER OPEN-CLOSE MECHANISM
Damper position is set automatically by damper motor
DM, damper switch and motor cam.
These components are operated by a signal that
judges if microwave cooking or convection cooking
operation is selected by the CPU unit.
Microwave Cooking:
Damper is in the open position, because a portion of
cooling air is channelled through the cavity to remove
steam and vapours given off from the heating foods.
It is then exhausted at the top of the oven cavity into a
condensation compartment.
Convection Cooking:
Damper is in the closed position, so that no hot air will
be allowed to leak out the oven cavity.
Damper Operation
1. When power supply cord is plugged in or when
the control unit resumes after energy save mode
finishes:
1-1. When power supply cord is plugged in, a signal
is sensed in the control unit, and operates shut-
off relay (RY8).
1-2. Contacts of shut-off relay (RY8) close, the
damper motor DM is energized, opening the
damper door.
1-3. When the damper is moved to the open position
by the damper cam, damper switch SW4 is
closed (ON position).
1-4. The signal of damper switch SW4 is re-sensed
in the control unit and shut-off relay (RY8) is
turned off.
1-5. The rated voltage to the damper motor DM is
stopped and the motor turns off.
2. When oven is microwave cooking:
Damper is in the open position
3. When oven is convection cooking:
3-1 Damper motor DM is energized right after the
oven is started.
3-2. When damper is in the closed position (damper
switch SW4 is OFF), its signal is sensed by the
control unit, and shut-off relay (RY8) is de-
energized.
3-3. The damper is held in the closed position during
the convection cooking operation.
3-4. At the end of the convection cooking, when the
fan motor FM stops, shut-off relay (RY8) is
energized, and the damper is returned to the
open position.
NOTE: If the damper door is not in the proper
position, closed during convection, grill or
dual, or open during microwave, the control
unit will stop oven operation after 1 minute.
Convection
Passa
g
e
Convection
Heatin
g
Element
Cooling
Fan
Convection
Moto
r
Convection
Fan
Grill Heating
Elements
Oven Cavity
Door
Turntable
Turntable Motor
Roller Stay
THERMISTOR
SENSING
VOLTAGE

SOI 12.06 FV 18/43 599 37 42-75
FUNCTION OF IMPORTANT COMPONENTS
4. Operation of damper is shown below.
Cooking Mode Operation of Damper
Microwave cooking Open
Convection cooking Closed
Grill; during backed up with
Convection heating element Closed
Grill; afther convection heting
element backed up has stopped Open
Dual (Microwave and Convection) Closed
Dual (Microwave and Grill) Open
Fire sensing condition Closed
TROBLESHOOTING 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.
IMPORTANT: If the oven becomes inoperative
Because of a blown fuse F2 (F8A) in
the monitored latch switch SW1 –
monitor switch SW3 circuit, check the
monitored latch switch SW1 and
monitor switch SW3 before replacing
the fuse F2 (F8A).

SOI 12.06 FV 19/43 599 37 42-75
TROBLESHOOTING GUIDE
BLOCKED COOLING FAN ●●●●
BLOCKED CONVECTION FAN ●●
●●
NO POWER AT WALL OUTLET ●
HOME FUSE OR BREAKER ● ●
MIS-ADJUSTMENT OF SWITCHES ●●●
● ●●●● ●
BLOCKED VENTILATION OPENINGS ●●●
OPENED WIRE HARNESS ●●● ● ● ● ●●●●● ● ●●● ● ● ● ●
SHORTED WIRE HARNESS ●
●● ● ● ● ●
OVEN LAMP OR SOCKET ●●
POWER SUPPLY CORD ●●
P
FOIL PATTERN ON P.W.B. ●
O
RELAY RY8 ●●●
O
RELAY RY7 ●●●
O
RELAY RY6 ●●●
O
RELAY RY5 ●
O
RELAY RY4 ●●●●●●
O
RELAY RY3 ●●●●
O
RELAY RY2 ●●●●●
O
RELAY RY1 ●●●●●
N
KEY UNIT ●●●
M
CONTROL PANEL ●●● ● ●●●●●●●● ● ●
TC TRANSFORMER ●
L
CONVECTION HEATING ELEMENT ●●●●
L
GRILL HEATING ELEMENT ●●
K
FUSE F2 F8A ●●●
J
FUSE F1 20A ●●
I
NOISE FILTER ●●
H
DAMPER MOTOR DM ●●●
H
CONVECTION FAN MOTOR ●●
●●
H
FAN MOTOR FM ●●●●
H
TURNTABLE MOTOR TM ●●
G
THERMAL CUT-OUT 170°C TC3 ●●
G
THERMAL CUT-OUT 170°C TC2 ●●
●
G
THERMAL CUT-OUT 125°C TC1 ●●●●
F
THERMISTOR ●● ● ●●●●●
E
DAMPER SWITCH SW4 ●
E
MONITOR SWITCH SW3 ●
●●●● ●
E
STOP SWITCH SW2 ●● ●
E
MONITORED LATCH SWITCH SW1 ●●●●
D
HIGH VOLTAGE CAPACITOR ●●
H.V. HARNESS ●●
C
H.V. RECTIFIER ASSEMBLY ●●
B
HIGH VOLTAGE TRANSFORMER ●●
A
MAGNETRON ●●
⁄
TEST PROCEDURE
POSSIBLE CAUSE
AND
DEFECTIVE PARTS
PROBLEM
Fuse F2 (F8A) blows when the door is opened. Home fuse blows when power cord is plugged into wall outlet. Fuse F1 20A blows when power cord is plugged into wall outlet. Nothing appears in display when power cord is plugged into wall ourlet and the door is opened and closed. Display does not operate propelrly when STOP button is pressed Oven lamp does not light when door is opened. (Display operates.) Oven no start when the START button is pressed (Display perates.) Oven lamp does not light and turntables motor does not operate. Fan motor does not operate. (Oven lamp lights.) Convection fan motor does not operate. (Fan motor operates.) Turntable motor does not operate. (Oven lamp lights.) Oven or any electrical parts (except fan motor) does not stop when cooking time is 0 or STOP button is pressed. Oven stops afther 4 minutes and 15 seconds since START button is pressed. (Except Microwave mode and Dual cook mode.) Display operate properly but all electrical parts do not operate. Oven goes into cook cicle but shuts down before end the cooking cycle. Afther cooking, the temperature of oven cavity is higher than 120°C but fan motor does not operate. The oven stops 1 minute afther starting. Oven seems to be operating but little or no heat is produced in oven load. (Microwave power control is set at 100%) Oven does not sem to be operating properly during variable cooking condition except 100% cooking condition. Oven goes into cook cycle but shuts down before end of cooking cycle. Convection cooking mode does not heat. Oven sems to be operating but the temperature in the oven cavity is lower or higher than present one. Grill heating element does not operate. Oven goes into cook cycle but shuts down before end of cooking cycle. Oven sems to be operative but little or no heat is produced in oven load.
(
Microwave
p
ower does not seem to be
g
enerated
p
ro
p
erl
y)
Oven sems to be operate but the temperature in the oven cavity is lower or hi
g
he
r
than the
p
resent one.
Convection heating element do not heat. Grill heating element does not heat.
CONDITION
OFF
CONDITION
COOKING
CONDITION
(COMMON MODE)
MICROWAVE
COOKING
CONDITION
CONVECTION
COOKING
CONDITION
GRILL COOKING
DUAL COOKING
CONDITION
(COMMON MODE)
DUAL COOKING
CONDITION
(MICRO./CONV.)
DUAL COOKING
(MICRO./GRILL)

SOI 12.06 FV 20/43 599 37 42-75
TEST PROCEDURES
PROCEDURE
LETTER COMPONENT TEST
A MAGNETRON TEST
NEVER TOUCH ANY PART IN THE CIRCUIT WITH YOUR HAND OR AN INSULATED
TOOL WHILE THE OVEN IS IN OPERATION.
CARRY OUT 3D CHECK
Isolate the magnetron from high voltage circuit by removing all leads connected to the
filament terminal.
To test for an open circuit filament use an ohmmeter to make a continuity test between
the magnetron filament terminals, the meter should show a reading of less than 1 ohm.
To test for a short circuit filament to anode condition, connect ohmmeter between one of
the filament terminals and the case of the magnetron (ground). This test should be
indicated an infinite resistance. If a low or zero resistance reading is obtained then the
magnetron should be replaced.
MICROWAVE OUTPUT POWER (IEC-60705-1988)
The following test procedure should be carried out with the microwave oven in a fully
assembled condition (outer case fitted). Microwave output power from the magnetron
can be measured by way of IEC 60705, i.e. it is measured by how much power the
water load can absorb. To measure the microwave output power in the microwave oven,
the relation of calorie and watt is used. When P(W) heating works for t(second),
approximately P x t/4.187 calorie is generated. On the other hand, if the temperature of
the water with V(ml) rises ΔT(°C) during this microwave heating period, the calorie of
the water is V x ΔT.
The formula is as follows;
P x t / 4.187 = V x Δ T+0.55 x mc (T2-T0)
Our condition for water load is as follows:
Room temperature.....................around 20°C
Water load..........................................1000 g
Heating time........................................47 sec.
T2......................................Final Temperature
P (W) = 4.187 x V x ΔT / t
Power supply Voltage........Rated voltage
Initial temperature(T1).............10 ± 1°C
Mass of container (mc)....................330 g
P = 90 x ΔT + 0.55 x mc (T2-T0)/47
Measuring condition:
1. Container
The water container must be a cylindrical borosilicate glass vessel having a maximum
material thickness of 3 mm and an outside diameter of approximately 190 mm.
2. Temperature of the oven and vessel.
The oven and the empty vessel are at ambient temperature prior to the start of the
test.
3. Temperature of the water
The initial temperature of the water is (10 ± 2)°C.
4. Select the initial and final water temperature so that the maximum difference
between the final water temperature and the ambient temperature is 5K.
5. Select stirring devices and measuring instruments in order to minimize addition or
removal of heat.
6. The graduation of the thermometer must be scaled by 0.1°C at minimum and an
accurate thermometer.
7. The water load must be (1000 ± 5) g.
8. “t” is measured while the microwave generator is operating at full power. Magnetron
filament heat-up time is not included.
NOTE: The operation time of the microwave ovens is “t + 3” sec. (3 sec. is magnetron
filament heat-up time.)