SERVICE MANUAL
MICROWAVE OVENS
Microwave Oven
 ELECTROLUX HOME PRODUCTS
Corso Lino Zanussi,30
I - 33080 PORCIA /PN (ITALY)
Tel +39 0434 394850
Fax +39 0434 394096
Publication No.
599 36 78-06
EN/SERVICE/FV
(Compact Solo)
MC1751E/MC1761E (EU)
MC1751E/MC1761E (UK)
EMS1750X/EM1760X (UK)
QN4025/QN4026 (SCANDINAVIA)
JMW1051/JMW1061 (A,D)
MOA4217 (D,K)
SOI
Edition: 01.2005
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599 36 78-06
TABLE OF CONTENTS
CAUTION, MICROWAVE RADIATION / GENERAL INFORMATION .............................................4
SERVICING......................................................................................................................................3
PRODUCT SPECIFICATIONS.........................................................................................................6
APPEARANCE VIEW.......................................................................................................................7
OPERATING SEQUENCE .............................................................................................................10
FUNCTION OF IMPORTANT COMPONENTS..............................................................................12
TROUBLESHOOTING CHART......................................................................................................13
TEST PROCEDURE ......................................................................................................................14
CONTROL PANEL ASSEMBLY.....................................................................................................22
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE ..........................................24
MICROWAVE MEASUREMENT....................................................................................................30
TEST DATA A GLANCE / WIRING / RE-WIRING .........................................................................31
SCHEMATIC DIAGRAMS ..............................................................................................................32
PICTORIAL DIAGRAM...................................................................................................................33
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CAUTION
CAUTION
MICROWAVE RADIATION
Personnel should not be exposed to the microwave energy which may radiate from the
magnetron or other microwave generating devices if it is improperly used or connected. All
input and output microwave connections, waveguides, flanges and gaskets must be secured.
Never operate the device without a microwave energy absorbing load attached.
Never look into an open waveguide or antenna while the device is energized.
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.
All the parts marked "*" on the schematic diagrams may cause
undue microwave exposure, by themselves, or when they are
damaged, loosened or removed.
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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
REMEMBER TO CHECK 4R
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.
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.
It is recommended that wherever possible faultfinding 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.
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.
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.
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
As part of our policy of continuous improvement, we reserve the right to
alter design and specifications without notice
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PRODUCT SPECIFICATIONS
SPECIFICATION
ITEM
DESCRIPTION
Power Requirements
230 Volts(EU)/230-240 Volts(UK)
50 Hertz
Single phase, 3 wire earthed
1.2 kW
800W watts nominal of RF microwave energy
(measured by way of IEC 60705)
Operating frequency of 2450 MHz
Width 454mm(including screws)
Height 357mm (including foot)
Depth 320mm
Width 285mm
Height 202mm
Depth 298mm
272mm
Jog/Touch Control System
Clock (1.00-12.59 or 0.00-23.59) - 12HR or 24HR
setting
Microwave Power for Variable Cooking
Repetition Rate;
Power Consumption
Power Output
Case Dimensions
Cooking Cavity Dimensions
Turntable diameter
Control Complement
HIGH ..........................
MEDIUM HIGH ..........
MEDIUM ....................
MEDIUM LOW ............
LOW .........................
Stir
Net weight
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Turn over
MICROWAVE POWER
LEVEL button
Weight
STOP button
Microwave
power level
START/QUICK button
Cooking in
progress
TIMER/WEIGHT knob
Stir
AUTOMATIC button
Turn over
MICROWAVE POWER
LEVEL button
Weight
STOP button
Microwave
power level
START/ QUICK button
Cooking in
progress
Approx, 16kg
6/33
Full power throughout
the cooking time
approx. 70% of Full
Power
approx. 50% of Full
Power
approx. 30% of Full
Power
approx. 10% of Full
Power
AUTOMATIC button
TIMER/WEIGHT knob
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APPEARANCE VIEW
OVEN
1 Front trim
2 Oven lamp
3 Control panel
4 Door opening button
5 Waveguide cover
6 Oven cavity
7 Seal packing
8 Door seals and sealing surfaces
9 Fixing points (4 points)
10 Ventilation openings
11 Outer cover
12 Rear cabinet
13 Power supply cord support clip
14 Power supply cord (EU)
15 Power supply cord (UK)
Turntable
Roller stay
Seal packing
1. Place the roller stay on the floor of
the oven cavity, engaging shaft into
turntable motor shaft.
2. Then place the turntable on roller
stay.
CONTROL PANEL
MC1751E/MC1761E/MOA4117
1
2
Digital Display
Indicators
The appropriate indicator will flash or light up,
just above each symbol according to the
instruction. When an indicator is flashing, press
the appropriate button (having the same symbol)
or carry out the necessary operation.
Stir
Turn oven
Weight
Microwave power level
Cooking in progress
3
4
5
6
7
8
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TIMER/WEIGHT knob
MICROWAVE POWER LEVEL button
AUTOMATIC PROGRAMMES button
Press to select one of the 12 automatic programmes.
START/QUICK button
STOP button
DOOR OPEN button
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APPEARANCE VIEW
CONTROL PANEL
EMS1750X/EMS1760X
1
2
Digital Display
Indicators
The appropriate indicator will flash or light up,
just above each symbol according to the
instruction. When an indicator is flashing, press
the appropriate button (having the same symbol)
or carry out the necessary operation.
Stir
Turn oven
Weight
Microwave power level
Cooking in progress
3
4
5
6
7
8
TIMER/WEIGHT knob
MICROWAVE POWER LEVEL button
AUTOMATIC PROGRAMMES button
Press to select one of the 12 automatic programmes.
START/QUICK button
STOP button
DOOR OPEN button
ZM175ST/ZM176ST
1
2
Digital Display
Indicators
The appropriate indicator will flash or light up,
just above each symbol according to the
instruction. When an indicator is flashing, press
the appropriate button (having the same symbol)
or carry out the necessary operation.
Stir
Turn oven
Weight
Microwave power level
Cooking in progress
3
4
5
6
7
8
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TIMER/WEIGHT knob
MICROWAVE POWER LEVEL button
AUTOMATIC PROGRAMMES button
Press to select one of the 12 automatic programmes.
START/QUICK button
STOP button
DOOR OPEN button
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APPEARANCE VIEW
QN4025/QN4026
1
2
Digital Display
Indicators
The appropriate indicator will flash or light up,
just above each symbol according to the
instruction. When an indicator is flashing, press
the appropriate button (having the same symbol)
or carry out the necessary operation.
Stir
Turn oven
Weight
Microwave power level
Cooking in progress
3
4
5
6
7
8
TIMER/WEIGHT knob
MICROWAVE POWER LEVEL button
AUTOMATIC PROGRAMMES button
Press to select one of the 12 automatic programmes.
START/QUICK button
STOP button
DOOR OPEN button
JMW1051/JMW1061
1
2
Digital Display
Indicators
The appropriate indicator will flash or light up,
just above each symbol according to the
instruction. When an indicator is flashing, press
the appropriate button (having the same symbol)
or carry out the necessary operation.
Stir
Turn oven
Weight
Microwave power level
Cooking in progress
3
4
5
6
7
8
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TIMER/WEIGHT knob
MICROWAVE POWER LEVEL button
AUTOMATIC PROGRAMMES button
Press to select one of the 12 automatic programmes.
START/QUICK button
STOP button
DOOR OPEN button
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OPERATION SEQUENCE
MICROWAVE OFF CONDITION
Closing the door activates the door interlock switch (monitored latch switch).
IMPORTANT
When the oven door is closed, the monitor switch contacts COM - NC must be open.
When the microwave oven is plugged in a wall outlet (230V/ 230-240v 50Hz), the noise filter is energized.
Figure 0-1 on page 32
NOTE: When the oven door is opened, the oven
lamp comes on at this time.
MICROWAVE COOKING CONDITION
HIGH COOKING
Enter a desired cooking time by rotating the time/weight knob
and start the oven by touching START pad.
Figure 0-2 on page 32
CONNECTED COMPONENTS RELAY
Oven lamp, Turntable motor
Power transformer
Fan motor
RY1
RY3
RY4
1. The line voltage is supplied to the primary winding of the power 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 wave length 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 + RY4 go back to their
home position. The circuits to the oven lamp, power 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.
SWITCH
CONTACT
Monitor switch
COM-NC
COM-NO
COM-NO
COM-NO
Monitored latch switch
Stop switch
DURING
COOKING
Open
Closed
Closed
Closed
CONDITION
DOOR OPEN
(NO COOKING)
Closed
Open
Open
Open
The circuits to the power transformer, fan motor and turntable motor are cut off when the monitored latch
switch is opened. 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 (SW2) 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 (SW3) must open their contacts(COM-NO) first. After that the contacts
(COM - NC) of the monitor switch (SW2) can be closed.
6-2 When the oven door is closed, the contacts (COM - NC) of the monitor switch (SW2) must be
opened first. The contacts (COM - NO) of the monitored latch switch (SW1) and stop switch (SW3)
are closed after.
6-3 When the oven door is opened and the contacts of the monitored latch switch (SW1) remain
closed, the fuse F1 will blow, because the monitor switch is closed and a short circuit is caused.
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OPERATION SEQUENCE
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 power
transformer intermittently within a 32-second time base through the vary contact. The following levels of
microwave power are given.
SETTING
HIGH
MEDIUM HIGH
Approx.
MEDIUM
Approx.
MEDIUM LOW
Approx.
LOW
Approx.
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.
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FUNCTION OF IMPORTANT COMPONENTS
DOOR OPEN MECHANISM
The door can be opened by pushing the door open button.
MONITORED LATCH SWITCH (SW1)
1. When the oven door is closed, the contacts
(COM - NO) must be closed.
2. When the oven door is opened, the contacts
(COM - NO) must be opened.
Door
Latch hook
SW3: Stop switch
MONITOR SWITCH (SW2)
1. When the oven door is closed, the contacts
(COM - NC) must be opened.
2. When the oven door is opened, the contacts
(COM - NC) must be closed.
3. If the oven door is opened and the contacts
(COM - NO) of the monitored latch switch
(SW1) fail to open, fuse F8A blows
simultaneously with closing the contacts
(COM - NC) of the monitor switch (SW2).
STOP SWITCH (SW3)
SW2: Monitor switch
SW1: Monitored latch switch
Latch heads
Figure D-1. Door Open Mechanism
1. When the oven door is closed, the contacts
(COM - NO)must be closed.
2. When the oven door is opened, the contacts (COM - NO) must be opened.
CAUTION: BEFORE REPLACING A BLOWN FUSE (F1) TEST THE MONITORED LATCH SWITCH
(SW1) AND MONITOR SWITCH (SW2) FOR PROPER OPERATION. (REFER TO
CHAPTER "TEST PROCEDURE".)
FUSE F1
1. The fuse F1 also blows when the H.V. rectifier, H.V. wire harness, H.V. capacitor, magnetron or
secondary winding of power transformer is shorted.
2. If the wire harness or electrical components are short-circuited, the fuse F1 blows to prevent an electric
shock or fire hazard.
THERMAL CUT-OUT 125°C TC01 (OVEN)
The thermal cut-out located on the top of the oven cavity is designed to prevent damage to the oven if the
foods in the oven catch fire due to over heating produced by improper setting of cook time or failure of control
unit. Under normal operation, the oven thermal cut-out remains closed. However, when abnormally high
temperatures are reached within the oven cavity, the oven thermal cut-out will open at
125°C, causing the oven to shut down. The defective thermal cut-out must be replaced with a new one.
THERMAL CUT-OUT 125°C TC02 (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 TC02 will open and line voltage to the high voltage transformer T
will cut off and operation of the magnetron MG will be stopped. The defective thermal cut-out must be
replaced with a new one.
TURNTABLE MOTOR
The turntable motor drives the turntable roller assembly to rotate the turntable.
FAN MOTOR
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
flows through the oven cavity to remove steam and vapours given off from the heating foods. It is then vented
through the exhaust air vents at the rear of oven cavity.
NOISE FILTER
The noise filter prevents the radio frequency interference that might flow back in the power circuit.
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TROUBLESHOOTING CHART
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. Check the monitored latch
switch and monitor switch before replacing the F8A fuse.
PROBLEM
Home fuse blows when power cord is
plugged into wall outlet.
"88:88"does not operate in display
when power cord is plugged into wall
outlet.
Display does not operate properly
when STOP button is touched.
OFF
CONDITION Oven lamp does not light, when door
is opened. (Display operates).
Oven does not start when START
button is touched.(Display operates).
Fan motor does not operate (Oven
lamp lights).
Turntable motor assembly does not
operate (Oven lamp lights).
Oven or electrical parts does not stop
when timer knob is at "0" or STOP
button is touched.
Display operates properly but all
electrical parts do not operate.
COOKING
Oven goes into cook cycle but shuts
CONDITION
down before end of cooking cycle.
Oven seems to be operating but little
or no heat is produced in oven load
(Microwave power control is set at
HIGH).
Oven does not seem to be operating
properly during variable cooking
condition(Oven operates properly at
HIGH).
CONDITION
Fuse F8A blows (F1)
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A B C
D E E E F F G H I
I
J J K L M
MAGNETRON
HIGH VOLTAGE TRANSFORMER
H.V. RECTIFIER ASSY
H.V. HARNESS
HIGH VOLTAGE CAPACITOR
MONITORED LATCH SWITCH
STOP SWITCH
MONITOR SWITCH
MAG THERMAL CUT-OUT 125°C
THERMAL CUT-OUT 125°C (OVEN)
FUSE F1
NOISE FILTER
TURNTABLE MOTOR
FAN MOTOR
TC TRANSFORMER
CONTROL UNIT
SWITCH UNIT
RELAY RY1,3,4
FOIL PATTERN ON P.W.B.
POWER SUPPLY CORD
SHORTED WIRE HARNESS
OPENED WIRE HARNESS
OVEN LAMP
BLOCKED VENTILATION OPENINGS
WRONG OPERATION
MIS-ADJUSTMENT OF SWITCHES
HOME FUSE OR BREAKER
NO POWER AT WALL OUTLET
BLOKED COOLING FAN
TEST PROCEDURE
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599 36 78-06
TEST PROCEDURES
PROCEDURE
LETTER
A
COMPONENT TEST
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. 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 ∆T (°C) during this microwave heating period, the calorie of the water is V x
∆T.
The formula is as follows;
P x t / 4.187 = V x ∆ T
P (W) = 4.187 x V x ∆T / t
Our condition for water load is as follows:
Room temperature..............around 20°C
Power supply Voltage.........Rated voltage
Water load.........1000 g
Initial temperature...........10 ± 2°C
Heating time....52 + 3 = 55 sec.
P = 80 x ∆T
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.
TEST PROCEDURES
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PROCEDURE
LETTER
COMPONENT TEST
NOTE: The operation time of the microwave oven is “t + 3” sec. 3 seconds are
needed for magnetron filament heat-up time.
Measuring method:
1. Measure the initial temperature of the water before the water is added to the
vessel.
(Example: The initial temperature T1 = 11°C)
2. Add the 1 litre water to the vessel.
3. Place the load on the centre of the turntable.
4. Operate the microwave oven at HIGH for the temperature of the water rises
by a value ∆ T of (10 ± 2) K.
5. Stir the water to equalize temperature throughout the vessel.
6. Measure the final water temperature. (Example: The final temperature
T2 = 21°C)
7. Calculate the microwave power output P in watts from above formula.
Initial temperature T1 = 11°C
Temperature after (52+ 3) = 55 sec.................................................... T2 = 21°C
Temperature difference Cold-Warm................................................. ∆T1 = 10°C
Measured output power
The equation is “P = 80 x ∆T” ................................... P = 80 x 10°C = 800Watts
JUDGEMENT: The measured output power should be at least ± 15 % of
the rated output power.
CAUTION: 1°C CORRESPONDS TO 80 WATTS. REPEAT MEASUREMENT
IF THE POWER IS INSUFFICIENT.
Heat up for 55 sec.
B
POWER TRANSFORMER TEST
WARNING: High voltages and large currents are present at the
secondary winding and filament winding of the power
transformer. It is very dangerous to work near this part when
the oven is on. NEVER make any voltage measurements of
the high-voltage circuits, including the magnetron filament.
CARRY OUT 3D CHECKS
Disconnect the leads to the primary winding of the power transformer.
Disconnect the filament and secondary winding connections from the rest of
the HV circuitry. Using an ohmmeter, set on a low range, it is possible to check
the continuity of all three windings. The following readings should be
obtained:a. Primary winding ............ 2 ohms approximately
b. Secondary winding ....... 160 ohms approximately
c. Filament winding ........... less than 1 ohm
If the reading obtained are not as stated above, then the power transformer is
probably faulty and should be replaced.
CARRY OUT 4R CHECKS
TEST PROCEDURES
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PROCEDURE
LETTER
C
COMPONENT TEST
HIGH VOLTAGE RECTIFIER ASSEMBLY TEST
CARRY OUT 3D CHECKS.
Isolate the high voltage rectifier assembly from the HV circuit. The high voltage
rectifier can be tested using an ohmmeter set to its highest range. Connect the
ohmmeter across the terminal B+C of the high voltage rectifier and note the
reading obtained. Reverse the meter leads and note this second reading.
The normal resistance is infinite in one direction and more than 100 kΩ in the
other direction.
CARRY OUT 4R CHECKS
ASYMMETRIC RECTIFIER TEST
ASYMMETRIC
RECTIFIER
CARRY OUT 3D CHECKS.
HIGH VOLTAGE
RECTIFIER
Isolate the high voltage rectifier assembly from the HV circuit. The asymmetric
rectifier can be tested using an ohmmeter set to its highest range across the
terminals A+B of the asymmetric rectifier and note the reading obtained.
Reverse the meter leads and note this second reading. If an open circuit is
indicated in both direction then the asymmetric rectifier is good. If an
asymmetric rectifier is shorted in either direction, then the asymmetric rectifier
is probably faulty and must be replaced. When the asymmetric rectifier is
defective, check whether magnetron, high voltage rectifier, high voltage wire or
filament winding of the power transformer is shorted.
CARRY OUT 4R CHECKS
NOTE: FOR MEASUREMENT OF THE RESISTANCE OF THE RECTIFIER,
THE BATTERIES OF THE MEASURING INSTRUMENT MUST HAVE
A VOLTAGE OF AT LEAST 6 VOLTS, BECAUSE OTHERWISE AN
INFINITE RESISTANCE MIGHT BE SHOWN IN BOTH
DIRECTIONS.
D
HIGH VOLTAGE CAPACITOR TEST
CARRY OUT 3D CHECKS
A. Isolate the high voltage capacitor from the circuit.
B. Continuity check must be carried out with measuring instrument which is set
to the highest resistance range.
C. A normal capacitor shows continuity for a short time (kick) and then a
resistance of about 10 MΩ after it has been charged.
D. A short-circuited capacitor shows continuity all the time.
E. An open capacitor constantly shows a resistance about 10 MΩ because of
its internal 10 MΩ resistance.
F. When the internal wire is opened in the high voltage capacitor, the
capacitor shows an infinite resistance.
G. The resistance across all the terminals and the chassis must be infinite
when the capacitor is normal.
If incorrect reading are obtained, the high voltage capacitor must be replaced.
CARRY OUT 4R CHECKS
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TEST PROCEDURES
PROCEDURE
LETTER
E
COMPONENT TEST
SWITCH TEST
CARRY OUT 3D CHECKS.
Isolate the switch to be tested and using an ohmmeter check between the
terminals as described in the following table.
Table: Terminal Connection of Switch
Plunger Operation
COM to NO
COM to NC
COM; Common terminal
Released
Open circuit
Short circuit
NO;
Normally open terminal
Depressed
Short circuit
Open Circuit
NC;
Normally close terminal
If incorrect readings are obtained, replace the switch.
CARRY OUT 4R CHECKS.
F
THERMAL CUT OUT TEST
CARRY OUT 3D CHECKS
Disconnect the leads from the terminals of the thermal cut-out. Then using an
ohmmeter, make a continuity test across the two terminals as described in the
below.
CARRY OUT 4R CHECKS
Table: Thermal Cut-out Test
Parts Name
Temperature of
"ON" condition
(closed circuit).
(°C)
Temperature of
"OFF" condition
(open circuit).
(°C)
Thermal cut-out
125°C TC01
Thermal cut-out
125°C TC02
This is not
reset able type
This is not
reset able type
Above 125°C
Indication of
ohmmeter
(When room
temperature is
approx. 20°C.)
Closed circuit
Above 125°C
Closed circuit
If incorrect readings are obtained, replace the thermal cut-out.
An open circuit thermal cut-out (MG) TC02 indicates that the magnetron has
overheated, this may be due to restricted ventilation, cooling fan failure.
An open circuit thermal cut-out (OVEN) TC01 indicates that the oven cavity
has overheated, this may be due to no load operation.
G
BLOWN FUSE F8A (F1)
CARRY OUT 3D CHECKS
If the fuse F8A (F1) is blown when the door is opened, check the primary
latch switch, monitor switch and monitor resistor.
If the fuse F8A (F1) is blown by incorrect door switching replace the
defective switch(es) and the fuse F8A (F1).
CARRY OUT 4R CHECKS
CAUTION: Only replace fuse with the correct value replacement.
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TEST PROCEDURES
PROCEDURE
LETTER
H
COMPONENT TEST
NOISE FILTER TEST
CARRY OUT 3D CHECKS
Disconnect the leads from the
terminals of the noise filter.
Using an ohmmeter, check between
the terminals as described in the
following table.
MEASURING POINTS
Between N and L
Between terminal N and WHITE
Between terminal L and RED
INDICATION OF OHMMETER
Open circuit
Short circuit
Short circuit
If Incorrect readings are obtained, replace the noise filter unit.
CARRY OUT 4R CHECKS
I
MOTOR WINDING TEST
CARRY OUT 3D CHECKS.
Disconnect the leads from the motor. Using an ohmmeter, check the
resistance between the two terminals as described in the table below.
Table: Resistance of Motor
Motors
Resistance
Fan motor
Approximately 290 Ω
Turntable motor
Approximately 12 - 15 kΩ
If incorrect readings are obtained, replace the motor.
CARRY OUT 4R CHECKS.
LIVE TEST FOR MOTOR WINDING
CAUTION: The following procedure requires the oven to be connected
to the supply and should only be used if the relevant "cold"
checks for the motor under test are inconclusive.
1. CARRY OUT 3D CHECKS.
2. Disconnect the leads from the primary of the high voltage transformer. Make
sure that the leads remain isolated from other oven components and
chassis (Use insulation tape if necessary) (See the pictorial diagram
page 33).
3. Connect the voltmeter, set to 250V AC, across the motor terminals. (Refer
to the relevant motor test procedure or pictorial diagram for the correct
terminal numbers.)
4. Arrange the meter in a position where it can be read during the test.
(Do not touch the meter, meter leads or oven circuitry while the oven is
active.)
5. Close the oven door.
6. Set the power level to 800W and set the relevant timer for about three (3)
minutes.
7. Note the reading on the meter and carefully observe the motor under test to
see if it is turning.
8. CARRY OUT 3D CHECKS.
9. Remove the test meter leads.
10.Reconnect the leads to the primary of the high voltage transformer.
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TEST PROCEDURES
PROCEDURE
LETTER
COMPONENT TEST
If a reading of the line voltage was obtained (step 7) but the motor was not
turning then it is faulty and should be replaced. If the meter indicated that the
no supply was present then the winding to the motor should be checked for
continuity or other circuit checks should be made, i.e. relays, switches.
J
TOUCH CONTROL PANEL ASSEMBLY TEST
The touch control panel consists of circuits including semiconductors such as
LSI, ICs, etc. Therefore, unlike conventional microwave ovens, proper
maintenance can not be performed with only a voltmeter and ohmmeter.
In this service manual, the touch control panel assembly is in three units,
Control unit, Switch Unit, and LED Unit. Troubleshooting by unit replacement is
described according to the symptoms indicated.
Control Panel.
The following symptoms indicate a defective control unit.
1. Switch Unit.
NOTE: Check switch unit lead wire harness connection
before replacement.
The following symptoms indicate a defective switch unit. Replace the
switch unit.
a) When touching the keys, a certain key produces no signal at all.
b) When touching a key, two figures or more are displayed.
c) When touching the keys, sometimes a key produces no signal.
2. Control Unit
The following symptoms indicate a defective control unit. Replace the
control unit, perform the switch unit test(Procedure K) to determine if
control unit is faulty.
2-1 In connection with keys.
a) When touching a key, a certain group of keys do not produce a signal.
b) When touching a key, no keys produce a signal.
2-2.In connection with indicators.
a) At a certain digit, all or some dots do not light up.
b) At a certain digit, brightness is low.
c) Only one indicator does not light up.
d) The corresponding dots 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.
h) When touching a tact switch, the control unit does not respond.
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. LED Unit
a) No backlight behind display.
b) Dull backlight behind display.
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TEST PROCEDURES
PROCEDURE
LETTER
K
COMPONENT TEST
SWITCH UNIT TEST
If the display fails to clear when the STOP key is depressed, first verify the
lead wire harness is marking good contact, verify that the stop switch
operates properly; that is the contacts are closed when the door is closed and
open when the door is open. If the stop switch is good, disconnect the lead
wire harness that connects the switch unit to the control unit and make sure
the stop switch is closed (either close the door or short the stop switch
connecter). Use the switch unit matrix indicated on the switch unit circuit and
place a jumper wire between the pins that correspond to the STOP key
making momentary contact. If the control unit responds by clearing with a
beep the switch unit is faulty and must be replaced. If the control unit does not
respond, it is a faulty and must be replaced. If a specific key does not
respond, the above method may be used (after clearing the control unit) to
determine if the control unit or switch unit is at fault.
SW
1
2
3
4
5
6
7
8
9
MC1751E/
Mc1761E/
MOA4117
EMS1750X/EMS1760X/
ZM175ST/ZM176ST/
QN4025/QN4026/
JMW1051/JMW1061
USAGE
Start/Quick
Not Used
Stop
Power Level
Not Used
Auto Programs
Not Used
Not Used
Not Used
USAGE
Start/Quick
Not Used
Stop
Not Used
Auto Programs
Not Used
Not Used
Power Level
Not Used
L
RELAY TEST
Remove the outer case and check voltage between Pin No 1and Pin No 3 of the 3
pin connector (A) on the control unit with an A.C. voltmeter.
The meter should indicate rated voltage, if not check oven circuit.
RY1,RY3 and RY4 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
SOI 01.05 FV
OPERATIONAL VOLTAGE
CONNECTED COMPONENTS
RY1
Approx. 12.0V D.C.
Oven lamp / Turntable motor
RY3
Approx. 12.0V D.C.
High voltage transformer
RY4
Approx. 12.0V D.C.
Fan motor
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TEST PROCEDURES
PROCEDURE
LETTER
M
COMPONENT TEST
PROCEDURES TO BE TAKEN WHEN THE FOIL PATTERN ON THE
PRINTED
WIRING BOARD (PWB) IS OPEN
To protect the electronic circuits, this model is provided with a fine foil pattern
added to the input circuit on the PWB, this foil pattern acts as a fuse. If the foil
pattern is open, follow the troubleshooting guide given below for repair.
Problem: POWER ON, indicator does not light up.
STEPS
OCCURRENCE
CAUSE OR CORRECTION
Check supply voltage and oven power
cord.
3
The rated AC voltage is not
present between Pin No. 5-1 of the
3 pin connector (A)
The rated AC voltage is not
present at primary side of low
voltage transformer.
Pattern at "a" and "b" are broken.
4
Pattern at "c" and "d" are broken.
1
2
Low voltage transformer or secondary
circuit defective.
check and repair.
*Insert jumper wire J1 and solder.
(CARRY OUT 3D CHECKS BEFORE
REPAIR)
*Insert the coil code 5028 24 08-00/9
between "c" and "d
(CARRY OUT 3D CHECKS BEFORE
REPAIR)
NOTE: *At the time of making these
repairs, make a visual
inspection of the varistor.
Check for burned damage. If
any abnormal condition is
detected, replace the
defective parts.
CARRY OUT 4D CHECKS
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CONTROL PANEL ASSEMBLY
OUTLINE OF CONTROL PANEL
The touch control section consists of the following units as shown in the touch control panel circuit.
(1) Switch Unit
(2) Control Unit
(3) LED Unit
The principal functions of these units and the signals communicated among them are explained below.
Switch Unit
The switch unit is composed of a matrix, signals generated in the LSI are sent to the switch unit
through P22, P23 and P24.
When a switch button is touched, a signal is completed through the switch unit and passed back to the
LSI through P50 and P51 to perform the function that was requested.
Control Unit
Control unit consists of LSI, power source circuit, relay circuit, back light circuit, synchronizing signal
circuit, reset circuit, buzzer circuit, and indicator circuit.
1) LSI
This LSI controls the tact switch strobe signal, relay driving signal, for oven function and
indicator signal.
2) Power Source Circuit
This circuit generates voltage necessary in the control unit.
Symbol
VC
Voltage
-5.0V
Application
LSI(IC1)
3) Synchronizing Signal Circuit
The power source synchronizing signal is available in order to compose a basic standard time in
the clock circuit. It accompanies a very small error because it works on commercial frequency.
4) ACL Circuit
A circuit to generate a signals which resets the LSI to the initial state when power is supplied.
5) Buzzer Circuit
The buzzer is responsive to signals from the LSI to emit audible sounds (tact switch touch sound
and completion sound).
6) Stop Switch
A switch to "tell" the LSI if the door is open or closed.
7) Relay Circuit
To drive the magnetron, fan motor, turntable motor, light the oven lamp.
8) Indicator Circuit
This circuit consists of 4-digits, 12-segments and 3-common electrodes using a Liquid Crystal
Display.
9) Encoder
The encoder converts the signal generated by LSI into the pulse signal, and the pulse signal is
returned to the LSI.
10) Back Light Circuit
A circuit to drive the back light (Light emitting diodes LD1 - LD3).
LED Unit
A circuit consisting of three light emitting diodes (LD1- LD3)which are driven by the control unit
and provide the backlight for the display.
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SERVICING
1. Precautions for Handling Electronic
Components
This unit uses CMOS LSI in the integral part of the
circuits. When handling these parts, the following
precautions should be strictly followed. CMOS LSI
have extremely high impedance at its input and
output terminals. For this reason, it is easily
influenced by the surrounding high voltage power
source, static electricity charge in clothes,
etc. and sometimes it is not fully protected by the
built-in protection circuit.
In order to protect CMOS LSI.
1) When storing and transporting, thoroughly wrap
them in aluminium foil. Also wrap all PW boards
containing them in aluminium foil.
2) When soldering, ground the technician as
shown in the figure and use grounded soldering
iron and work table.
approx. 1 M ohm
2. Servicing of Touch Control Panel
We describe the procedures to permit servicing
of the touch control panel of the microwave
oven and the precautions you must take when
doing so. To perform the servicing, power to the
touch control panel is available either from the
power line of the oven itself or from an external
power source.
(1) Servicing the touch control panel with
power line of the oven:
CAUTION:
THE HIGH VOLTAGE TRANSFORMER OF THE
MICROWAVE OVEN IS STILL LIVE DURING
SERVICING AND PRESENTS A HAZARD.
Therefore, before checking the performance of
the touch control panel,
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 these leads remain isolated from
other components and oven chassis by using
insulation tape.
6) After that procedure, re-connect the power
supply cord.
After checking the performance of the touch
control panel,
1) Disconnect the power supply cord.
2) Open the door and block it open.
3) Re-connect the leads to the primary of the
power transformer.
4) Re-install the outer case (cabinet).
5) Re-connect the power supply cord after the
outer case is installed.
SOI 01.05 FV
6) Run the oven and check all functions.
A. On some models, the power supply cord
between the touch control panel and the oven
itself is so short that the two can’t be separated.
For those models, check and repair all the
controls (sensor-related ones included) of
the touch control panel while keeping it
connected to the oven.
B. On some models, the power supply cord
between the touch control panel and the oven is
long enough that they may be separated from
each other. For those models, it is possible to
check and repair the controls of the touch
control panel while keeping it apart from the
oven; in this case you must short both ends of
the door sensing switch (on PWB) of the touch
control panel with a jumper, which activates an
operational state that is equivalent to the oven
door being closed.
(2) Servicing the touch control panel with
power supply from an external power
source:
Disconnect the touch control panel completely
from the oven, and short both ends of the door
sensing switch (SW3: STOP SWITC on PWB)
of the touch control panel, which activates an
operational state that is equivalent to the oven
door being closed. Connect an external power
source to the power input terminal of the touch
control panel, then it is possible to check and
repair the controls of the touch control panel.
3. Servicing Tools
Tools required to service the touch control panel
assembly.
1) Soldering iron: 30W
(It is recommended to use a soldering iron with
a grounding terminal.)
2) Others: Hand tools
4. Other Precautions
1) Before turning on the power source of the
control unit, remove the aluminium foil applied
for preventing static electricity.
2) Connect the connectors of the key unit to the
control unit being sure that the lead wires are
not twisted.
3) After aluminium foil is removed, be careful that
abnormal voltage due to static electricity etc. is
not applied to the input or output terminals.
4) Attach connectors, electrolytic capacitors, etc.
to PWB, making sure that all connections are
tight.
5) Be sure to use specified components where
high precision is required.
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COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE
WARNING: Avoid possible exposure to microwave energy. Please follow the instructions
below before operating the oven.
1. CARRY OUT 3D CHECKS.
2. Make sure that a definite "click" can be heard 2. Door hinges or latch hook is damaged.
when the microwave oven door is unlatched. 3. The door seal is damaged.
(Hold the door in a closed position, then
4. The door is bent or warped.
push the open button slowly. This causes
5. There are defective parts in the door interlock
the latch heads to rise, it is then possible to
system.
hear a "click" as the door switches operate.)
6. There are defective parts in the microwave
3. Visually check the door and cavity face plate
generating and transmission assembly.
for damage (dents, cracks, signs of arcing
7. There is visible damage to the oven.
etc.).
Do not operate the oven:
Carry out any remedial work that is necessary
1. Without the RF gasket (Magnetron).
before operating the oven.
2. If the wave guide or oven cavity are not intact.
Do not operate the oven if any of the following
3. If the door is not closed.
conditions exist;
4. If the outer case (cabinet) is not fitted.
1. Door does not close firmly.
Please refer to ‘OVEN PARTS, CABINET PARTS, DOOR PARTS’, when carrying out any of the
following removal procedures:
BUILT IN FRAME ASSEMBLY REMOVAL
To remove the built in frame assembly, proceed
as follows.
1. Remove the four screws securing the frame
assembly to the oven cavity, (two from the
top and two from the hinge side).
2. Remove the two screws securing the frame
assembly to the control panel frame
(accessed from the back of the frame).
3. Open the oven door fully.
4. Push down the built in frame assembly at
the bottom, where it meets the cavity face.
5. Pull the built in frame assembly away from the
cavity face
6. Now the built in frame assembly is free.
TOP
SCREWS
C.P. SECURING
SCREWS
HINGE SEDE
SCREWS
PRESS
HERE
OUTER CASE REMOVAL
To remove the outer case, proceed as follows.
1. Disconnect oven from power supply.
2. Open door and wedge open.
3. Remove the two screws from the rear
intake duct.
4. Slide the rear intake duct up and pull it
away from the oven cavity.
5. Remove the screws from the rear(4), along
the side edges(4 hinge side, 3 control panel
side) and from the top(2 control panel side).
SOI 01.05 FV
6. Slide the entire case back about 3cm to free it from
the retailing clips on the cavity face plate.
7. Lift the entire case from the oven.
8. Discharge the H.V capacitor before carrying any
further work.
9. Do not operate the oven with the outer case
removed.
CAUTION: DISCHARGE HIGH VOLTAGE
CAPACITOR BEFORE TOUCHING ANY
OVEN COMPONENTS OR WIRING.
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COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE
HIGH VOLTAGE COMPONENTS REMOVAL
(HIGH VOLTAGE CAPACITOR AND HIGH VOLTAGE RECTIFIER ASSEMBLY)
To remove the components, proceed as
follows.
1. CARRY OUT 3D CHECKS
2. Disconnect all the leads and terminal of high
voltage rectifier from high voltage capacitor.
3. Remove one (1) screw holding earth side
terminal of high voltage rectifier, and remove
capacitor holder from the base plate.
4. Remove the capacitor from the capacitor
holder.
5. Now the high voltage rectifier and capacitor
should be free.
CAUTION:
WHEN REPLACING HIGH
VOLTAGE RECTIFIER ASSEMBLY,
ENSURE THAT THE CATHODE
(EARTH) CONNECTION IS
SECURELY FIXED TO THE
CAPACITOR HOLDER AND
BASEPLATE WITH AN EARTHING
SCREW.
HIGH VOLTAGE TRANSFORMER REMOVAL
1. CARRY OUT 3D CHECKS
2. Disconnect the filament leads of the power
transformer from high voltage capacitor and the
magnetron.
3. Disconnect the H.V. secondary wire from the
power transformer.
4. Remove the four (4) screws holding the
transformer to base plate (from the under side).
5. Remove the transformer from the baseplate by
sliding it away from the oven cavity and lifting it.
6. Now, the power transformer is free.
MAGNETRON REMOVAL
1. CARRY OUT 3D CHECKS.
2. Disconnect the H.V. wire B and filament lead of
the transformer from the magnetron.
3. Move the air intake duct to left.
4. Carefully remove two (2) screws holding
magnetron to the waveguide.
5. Remove the magnetron from the waveguide with
care so the magnetron antenna is not hit by any
metal object around the antenna.
CAUTION: WHEN REPLACING THE MAGNETRON,
BE SURE THE R.F. GASKET IS IN
PLACE AND THE MAGNETRON
MOUNTING SCREWS ARE TIGHTENED
SECURELY. REINSTALL THE
MAGNETRON TO WAVE GUIDE
FLANGE WITH THE TWO (2) SCREWS
DIAGONALLY.
ENSURE THE MAGNETRON WIRING IS
REFITTED IN ACCORDANCE WITH
THE PICTORIAL DIAGRAM ON PAGE
33 (FA AND F).
CONTROL PANEL ASSEMBLY REMOVAL
1. CARRY OUT 3D CHECKS.
2. Disconnect the main wire harness from the
control panel.
3. Remove the one (1) screw holding the control
panel to the oven cavity.
4. Lift the control panel assembly and pull it
forward. Now, the control panel assembly is
free.
TURNTABLE MOTOR REMOVAL
1. Disconnect the oven from the power supply.
2. Remove the turntable motor cover by snipping
off the material in four corners.
3. Where the corners have been snipped off bent
corner areas flat. No sharp edge must be
evident after removal of turntable motor cover.
4. Disconnect the wire leads from the turntable
motor and remove the one (1) screw holding the
turntable motor.
5. Turntable motor is now free.
6. After replacement use one (1) screw to fit the
turntable motor cover.(code 5028 05 76-00/5).
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COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE
FAN MOTOR REPLACEMENT
REMOVAL
1. CARRY OUT 3D CHECKS.
2. Disconnect the wire leads from the fan
motor.
3. Remove the two (2) screws holding the fan
motor to the oven cavity back plate. The fan
motor is now free.
4. Remove the fan blade from the fan motor
shaft according
to the following procedure.
1) Hold the edge of the rotor of the fan motor by
using a pair of groove joint pliers.
CAUTION:
• Make sure that any pieces do not enter the
gap between the rotor and the stator of
the fan motor.
Because the rotor is easy to be shaven by
pliers and metal pieces may be produced.
• Do not let the pliers touch the coil of the
fan motor because the coil may be cut or
damaged.
• Do not distort the bracket by touching with
the pliers.
2) Remove the fan blade from the shaft of the
fan motor by pulling and rotating the fan
blade with your hand.
3) Now, the fan blade will be free.
CAUTION:
• Do not use this removed fan blade again.
Because the hole (for shaft) of it may
become bigger than a standard one.
INSTALLATION
1. Install the fan blade to the fan motor shaft according
to the following procedure.
1) Hold the centre of the bracket which supports the
shaft of the fan motor on a flat table.
2) Install the fan blade to the shaft of fan motor by
pushing the fan blade with a small, light weight,
ball peen hammer or rubber mallet.
CAUTION:
• Do not hit the fan blade when installing
because the bracket may be deformed.
• Make sure that the fan blade rotates smoothly
after installation.
• Make sure that the axis of the shaft is not
slanted.
2. Install the fan motor to the oven cavity back plate
with the two (2) screws.
3. Re-connect the wire leads to the fan motor,
referring to the pictorial diagram.
Coil
Groove joint pliers
Shaft
Stator
Gap
Axis
Rotor
Bracket
Stator
These are the position
that should be pinched
with pliers
Rotor
Rear view
Side view
Shaft
Table
SOI 01.05 FV
Center of
bracket
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COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE
OVEN LAMP REMUVAL
1. CARRY OUT 3D CHECKS.
2. Disconnect the wire lead from the oven lamp
3. Lift up the oven lamp from the clips of the air
intake duct.
4. Now, the oven lamp is free.
Lock
Bulb
Socket
Oven lamp
POWER SUPPLY CORD REPLACEMENT
Removal
1. CARRY OUT 3D CHECKS.
2. Remove the wiring of the main harness from the
noise filter.
3. Remove the two (2)screws securing the N.F.U.
holder to the baseplate.
4. Remove the one(1) screw holding the
green/yellow (earth wire) to the N.F.U. holder
assembly.
5. Release the power supply cord stopper from the
N.F.U. holder assembly by sliding it out.
6. Remove the wiring of the power cord from the
noise filter.
7. Now the power supply cord is free.
Re-install
1. Insert the moulding cord stopper of power
supply cord into the cut-out of the N.F.U. holder
assembly, referring to the Figure C-1(b).
Installation of Power supply cord.
2. Install the earth wire lead of power supply cord
to the N.F.U. holder assembly with one (1)
screw and tighten.
3. Connect the brown and blue wire leads of
power supply cord to the noise filter correctly,
referring to the Pictorial Diagram.C-1(a)
4. Re-fit the N.F.U. holder assembly to the base
plate with the two (2) screws.
5. Connect the main harness wiring to the noise
filter correctly, referring to the Pictorial
Diagram(figure C - 1(a)).
Noise filter
Power supply cord
Brown Wire
Moulded
Cord
Stopper
POWER SUPPLY
CORD
Blue Wire
Green / Yellow
Wire
MOULDING
CORD
STOPPER
GROMMET
MOULDING
Noise filter holder
Figure C-1 (a) Replacement of Power Supply Cord
Figure C-1 (b). Installation of Power Supply
Cord
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COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE
MONITORED LATCH SWITCH, MONITOR SWITCH AND
STOP SWITCH REMOVAL
1. CARRY OUT 3D CHECKS.
2. Disconnect the wire leads from the switches
and control panel.
3. Remove the control panel assembly from the
oven cavity front flange. Referring to chapter
"CONTROL PANEL ASSEMBLY
REMOVAL".
4. Remove the one (1) screw holding the latch
hook to the oven flange.
5. Remove the latch hook assembly from the
oven flange.
6. To remove the switch.
6-1. With pushing outward on the tab that is
holding the switch, turn the switch so that the
post is an axis.(Monitor Switch).
With pushing outward on the tab that is
holding the switch, slide the switch out of the
latch hook.(Stop Switch and Monitored Latch
switch).
6-2. Pull out the switch from the latch hook. Do
not break the post or tab of the latch hook.
6-3. Now the switch is free.
Re-install
1. Re-install each switch in its place. The
monitored latch switch is in the lower
position and the monitor switch is
in the middle position. The stop switch is in
the upper position.
2. Re-connect wire leads to each switch. Refer
to charter “Pictorial Diagram”.(page 32)
3. Secure latch hook (with one (1) mounting
screw) to oven.
flange.
4. Re-install the control panel assembly to the oven
cavity front flange.
5. Re-connect wire leads to the control unit. Refer to
chapter “Pictorial Diagram”.(page 33).
6. Make sure that monitor switch is operating properly
and check continuity of the monitor circuit. Refer to
chapter “Test Procedure”, and Adjustment
Procedure below.
Latch hook
SW3:Stop switch
Tab
Tab
SW2:Monitor switch
SW1:Monitored latch switch
Tab
Figure C-2. Latch Switches Removal
MONITORED LATCH SWITCH, MONITOR SWITCH AND
STOP SWITCH ADJUSTMENT
1. CARRY OUT 3D CHECKS.
If the monitored latch switch, stop switch and
monitor switch do not operate properly due
to a misadjustment, the following adjustment
should be made.
2. Loosen the one (1) screw holding the latch
hook to the flange of the oven front face.
3. With the door closed, adjust latch hook by
moving it up and down. In and out play of
the door allowed by the upper and lower
position of the latch hook should be less
than 0.5mm. The vertical position of the
latch hook should be adjusted so that the
stop switch and the monitored latch switch
are activated with the door closed.
4. Secure the screws firmly.
5. Check the operation of all switches. If each
switch has not activated with the door
closed, loosen screw and ad just the latch
hook position.
After adjustment, make sure of the
following.
1. In and out play of the door remains less than
0.5mm when in the latched position.
2. The monitored latch switch and stop switch
interrupt the circuit before the door can be
opened.
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3. The monitor switch contacts (COM-NC) close
when the door is opened.
4. Re-install outer case and check for microwave
leakage around the door with an approved
microwave survey meter. (Refer to Microwave
Measurement Procedure.)
Door
Latch hook
SW3: Stop switch
SW2: Monitor switch
Latch heads
SW1: Monitored latch
switch
Figure C-3. Latch Switch Adjustments
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COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE
REMOVAL
1. Disconnect the power supply cord.
2. Open the door slightly and remove the built in
frame assembly(Ref: to chapter built in frame
assembly removal).
3. Remove the choke cover taking care not to
break clips by inserting an iron plate (thickness
of about 0.5mm) or flat type screw driver to the
gap between the choke cover and door panel
as shown Figure C-4 to free the engaged
parts.
4. Release choke cover from door panel.
5. Now choke cover is free.
Choke Cover
Putty Knife
Door Frame
Figure C-4. Door Disassembly
6. Release two (2) pins of door panel from two (2)
holes of upper and lower oven hinges by lifting
up.
7. Remove door assy by removing screws (4).
8. Release door panel from tabs of door frame and
remove door frame.
9. Now, door panel with inner sealer film is free.
10.Tear inner sealer film from door panel.
11.Now, door panel is free.
12.Slide latch head upward and remove it from
door frame with releasing latch spring from door
frame and latch head.
13.Now, latch head and latch spring are free.
RE-INSTALL
1. Re-install latch spring to the head. Re-install
latch spring to the door frame. Re-install latch
head to the door frame.
2. Re-install door panel to door frame by fitting tabs
of door frame to holes of door panel.
3. Put sealer film on door panel. Refer to “Inner
Sealer Film” and figure C-6, on how to handle
the new film.
4. Catch two (2) pins of door panel on two (2) hole
of upper and lower oven hinges.
5. Re-install choke cover to door panel by pushing.
SOI 01.05 FV
Note: After any service to the door;
(A) Make sure that monitored latch switch, stop
switch and monitor switch are operating
properly. (Refer to chapter “Test
Procedures , Switch Test page 17”.).
(B) An approved microwave survey meter
should be used to assure compliance with
proper microwave radiation emission
limitation standards.
After any service, make sure of the following :
1. Door latch heads smoothly catch latch hook
through latch holes and that latch head goes
through center of latch hole.
2. Deviation of door alignment from horizontal line
of cavity face plate is to be less than 1.0mm.
3. Door is positioned with its face pressed toward
cavity face plate.
4. Check for microwave leakage around door with
an approved microwave survey meter. (Refer to
Microwave Measurement Procedure.)
Note: The door on a microwave oven is
designed to act as an electronic seal
preventing the leakage of microwave
energy from oven cavity during
cook cycle. This function does not require
the door be air-tight, moisture
(condensation)-tight or light-tight.
Therefore, occasional appearance
of moisture, light or sensing of gentle
warm air movement around oven door is
not abnormal and does not indicate
leakage of microwave energy from the
oven cavity.
PIN
UPPER
OVEN HINGE
DOOR SUB
ASSEMBLY
SLIT CHOCHE
DOOR
PANEL
LOWER
OVEN
HINGE
CHOKE COVER
LOWER
OVEN HINGE
Figure C-5. Door Replacement
NOTE: When carrying out any repair to the
door, do not bend or warp the slit
choke (tabs on the door panel
assembly) to prevent microwave
leakage.
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COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE
INNER SEALER FILM
Door film
Backing film
Installation
1. Tear away the backing film.
3. Put the pasted side of the inner sealer film
on the door panel.
Finger tab
Figure C-6. Inner Sealer Film
MICROWAVE MEASUREMENT
After adjustment of door latch switches, monitor
switch and door are completed individually or
collectively, the following leakage test must be
performed with a survey instrument and it must be
confirmed that the result meets the requirements
of the performance standard for microwave oven.
REQUIREMENT
The safety switch must prevent microwave
radiation emission in excess of 5mW/cm2 at any
point 5 cm or more from external surface of the
oven.
PREPARATION FOR TESTING:
Before beginning the actual test for leakage,
proceed as follows;
1. Make sure that the test instrument is operating
normally as specified in its instruction booklet.
Important:
Survey instruments that comply with the
requirement for instrumentations as prescribed
by the performance standard for microwave
ovens must be used for testing.
Recommended instruments are:
NARDA 8100
NARDA 8200
HOLADAY HI 1500
SIMPSON 380M
2. Place the oven tray into the oven cavity.
3. Place the load of 275 ± 15ml of water initially at
20 ± 5°C in the center of the oven tray. The
water container should be a low form of 600 ml
beaker with inside diameter of approx. 8.5cm
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.
4. Close the door and turn the oven ON with the
timer set for several minutes. If the water begins
to boil before the survey is completed, replace it
with 275ml of cool water.
5. Move the probe slowly (not faster that
2.5cm/sec.) along the gap.
6. The microwave radiation emission should be
measured at any point of 5cm or more from the
external surface of the oven.
Microwave leakage measurement at 5 cm distance
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599 36 78-06
TEST DATA AT A GLANCE
Parts
Thermal cut-out (OVEN)
Oven lamp
High voltage capacitor
Symbol
TC01
OL
C
Magnetron
MG
Power transformer
T
Fuse
thermal cut-out(Magnetron)
F1
TC02
Value / Data
125°C
240-250V 25W
0.91µF AC 2100V(EU)
0.88µF AC 2100V(UK)
Filament < 1Ω
Filament – chassis ∞ ohm.
Filament winding < 1Ω
Secondary winding Approx. 160Ω.
Primary winding Approx. 2 Ω.
F8A 250V
125°C
WIRING/RE-WIRING
WARNING: WIRING / RE-WIRING.
Before carrying out any work; carry out 3D
checks.
1. Disconnect the supply
2. Door opened and wedge open.
3. Discharge the high voltage capacitor.
RE-WIRING.
Ensure the following:
1. Wires must not touch:
a) High voltage parts.
(Magnetron, high voltage transformer, high
voltage capacitor and high voltage rectifier).
c) Sharp edges.
(Bottom plates, oven cavity, waveguide
flange, chassis support and other metallic
parts).
d) Movable parts.
( Fan blade, any motor, switch).
2. Positive lock connectors are fitted correctly.
Ensure the locking pin is located correctly.
3. Wires are connected correctly as per pictorial
diagram.
4. No wire leads are trapped by the outer wrap.
b) Parts that become hot.
(Heating elements, oven lamp, oven cavity
magnetron and high voltage transformer).
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599 36 78-06
SCHEMATIC DIAGRAMS
MAGNETRON
THERMAL
CUT- OUT 125°C
HIGH VOLTAGE
TRANSFORMER
RECTIFIER
CAPACITOR
TURNTABLE
MOTOR
OVEN LAMP
STOP SWITCH
FAN MOTOR
TRANSFORMER T/C
FUSE
NOISE SUPRESSION COIL
OVEN THERMAL
CUT- OUT 125°C
NIOSE FILTER
MONITORED
LATCH SWITCH
MONITOR
SWITCH
Figure 0-1 Oven Schematic-OFF Condition, Door Closed.
* INDICATES COMPONENTS WITH
POTENTIAL ABOVE 250V
MAGNETRON
THERMAL
CUT- OUT 125°C
CAPACITOR
TURNTABLE
MOTOR
FAN MOTOR
OVEN LAMP
STOP SWITCH
RECTIFIER
HIGH VOLTAGE
TRANSFORMER
TRANSFORMER T/C
FUSE
NOISE SUPRESSION COIL
OVEN THERMAL
CUT- OUT 125°C
NIOSE FILTER
MONITORED
LATCH SWITCH
MONITOR
SWITCH
Figure 0-2 Oven Schematic-ON Condition, Door Closed.
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599 36 78-06
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CONTROL UNIT
SWITCH UNIT
LED BOARD
MONITORED LATCH SWITCH
MONITOR SWITCH
STOP SWITCH
TURNTABLE MOTOR
MAG.
THERMAL
CUTOUT
OVEN
THERMAL
CUTOUT
OVEN LAMP
FAN MOTOR
MAINS SUPPLY CORD
33/33
POWER TRANSFORMER
HV RECTIFIER
HV CAPACITOR
SHORT
PROCTETOR
FA
HIGH VOLTAGE COMPONENTS
NOISE FILTER UNIT
PICTORIAL DIAGRAMS
599 36 78-06