Service personals 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.
Never operate the oven until the following points are ensured.
(A) The door is tightly closed.
(B) The door brackets and hinges are not defective.
(C) The door packing is not damaged.
(D) The door is not deformed or warped.
(E) There is 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 parts list are used at voltages more than 250V.
Removal of the outer wrap gives access to potentials above 250V.
All the parts marked "∆" on parts list may cause undue microwave exposure, by themselves, or when they are damaged, loosened or removed.
Never operate the oven until the following points are ensured.
(A) The door is tightly closed.
(B) The door brackets and hinges are not defective.
(C) The door packing is not damaged.
(D) The door is not deformed or warped.
(E) There is 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 parts list are used at voltages more than 250V.
Removal of the outer wrap gives access to potentials above 250V.
All the parts marked "∆" on parts list may cause undue microwave exposure, by themselves, or when they are damaged, loosened or removed.
THE
WIRES IN THIS MAINS LEAD ARE COLORED IN ACCORDANCE WITH THE FOLLOWING CODE
GREEN
& YELLOW: EARTH
BLUE : NEUTRAL
BROWN : LIVE
BLUE : NEUTRAL
BROWN : LIVE
APPEARANCE
VIEW
Touch
control panel
OPERATION SEQUENCE
OFF CONDITION
Closing the door activates all door interlock switches (1st. latch switch, 2nd. latch switch and stop 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, rated voltage is supplied to the point A3+A5 in the control unit.
1. The display shows SHARP , MICRO-WAVE and OVEN .
2. To set any programmes or set the clock, you must first touch the STOP/CLEAR pad.
3. [ : ]appears in the display.
NOTE: When the oven door is opened, the oven lamp comes on at this time.
HIGH
COOKING
Enter a desired cooking time with the touching NUMBER pad and start the oven with touching START pad.
Enter a desired cooking time with the touching NUMBER pad and start the oven with touching START pad.
CONNECTED
COMPONENTS RELAY
Oven lamp, Fan motor, Turntable motor RY1
Power transformer RY2
Oven lamp, Fan motor, Turntable motor RY1
Power transformer RY2
1. Rated
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 channeled 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 signal tone is heard and the relays RY1+RY2 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.
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 channeled 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 signal tone is heard and the relays RY1+RY2 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.
The circuits to the power transformer, fan motor and turntable motor are cut off when the 1st. latch switch, 2nd. Latch switch, and stop switch 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.
MONITOR SWITCH CIRCUIT
The monitor switch is mechanically controlled by oven door, and monitors the operation of the 1st and 2nd. Latch switches.
1. When the oven door is opened during or after the cycle of a cooking program, the 1st. latch switch, 2nd. Latch switch and stop switch must open their contacts first. After that the contacts (COM-NC) of the monitor switch can be closed.
2. When the oven door is closed, the contacts (COMNC) of the monitor switch must be opened. After that the contacts of the 1st. latch switch, 2nd. latch switch and stop switch are closed.
3. When the oven door is opened and the contacts of the-1st. latch switch, 2nd. latch switch remain closed. The fuse M8A will blow, because the monitor switch is closed and a short circuit is caused.
MEDIUM HIGH, MEDIUM, MEDIUM LOW, LOW COOKING
When the microwave oven is preset for variable cooking power, 230-240 volts A.C. power is supplied to the power transformer intermittently within a 32-second time base through the relay contact which is coupled with the current-limiting relay. The following levels of microwave power are given.
NOTE: The ON/OFF time ratio does not exactly correspond to the percentage of microwave power, because approx. 2 seconds are needed for heating up the magnetron filament.
FUNCTION OF IMPORTANT COMPONENTS
DOOR OPEN MECHANISM
The door is opened by pushing the open button on the control panel, refer to the Figure D-1. When the open button is pushed, the open button pushes up the switch lever, and then the switch lever pushes up the the latch head. The latch heads are moved upward and released from latch hook. Now the door will open.
1ST.
LATCH SWITCH, 2ND. LATCH SWITCH AND STOP SWITCH
1. When the oven door is closed, the contacts COM-NO) must be closed.
2. When the oven door is opened, the contacts .(COMNO) must be opened.
MONITOR SWITCH
1. When the oven door is closed, the contacts (COM-NC) must be opened.
2. When the oven door is opened, the contacts (COMNC) must be closed.
3. If the oven door is opened and the contacts (COM-NO) of the 1st. latch switch and 2nd. latch switch fail to open, the fuse M8A blows simultaneously with closing the contacts (COM-NC) of the monitor switch.
CAUTION: BEFORE REPLACING A BLOWN FUSE M8A TEST THE 1ST. LATCH SWITCH, 2ND. LATCH SWITCH MONITOR SWITCH AND MONITOR RESISTOR FOR PROPER OPERATION.
1. When the oven door is closed, the contacts COM-NO) must be closed.
2. When the oven door is opened, the contacts .(COMNO) must be opened.
MONITOR SWITCH
1. When the oven door is closed, the contacts (COM-NC) must be opened.
2. When the oven door is opened, the contacts (COMNC) must be closed.
3. If the oven door is opened and the contacts (COM-NO) of the 1st. latch switch and 2nd. latch switch fail to open, the fuse M8A blows simultaneously with closing the contacts (COM-NC) of the monitor switch.
CAUTION: BEFORE REPLACING A BLOWN FUSE M8A TEST THE 1ST. LATCH SWITCH, 2ND. LATCH SWITCH MONITOR SWITCH AND MONITOR RESISTOR FOR PROPER OPERATION.
MONITOR
RESISTOR R 0.8Ω 20W
The monitor resistor prevents the fuse M8A bursting when the fuse M8A blows due to the operation of the monitor switch.
ASYMMETRIC RECTIFIER
The asymmetric rectifier is a solid state device that prevents current flow in both directions. And it prevents the temperature rise of the power transformer by blowing the fuse M8A when the high voltage rectifier is shorted.
The monitor resistor prevents the fuse M8A bursting when the fuse M8A blows due to the operation of the monitor switch.
ASYMMETRIC RECTIFIER
The asymmetric rectifier is a solid state device that prevents current flow in both directions. And it prevents the temperature rise of the power transformer by blowing the fuse M8A 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 blowing the fuse M8A.)
1. The high voltage rectifier is shorted by any causes when microwave 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 power transformer.
5. The large electric currents beyond 8A flow through the primary winding of the power transformer.
6. The fuse M8A blows by the large electric currents.
7. The power supply to all the electrical parts is cut off
1. The high voltage rectifier is shorted by any causes when microwave 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 power transformer.
5. The large electric currents beyond 8A flow through the primary winding of the power transformer.
6. The fuse M8A blows by the large electric currents.
7. The power supply to all the electrical parts is cut off
FUSE
M8A
1. The fuse M8A blows when the contacts (COM-NO) of the 1st. latch switch and 2nd. latch switch remain closed with the oven door open and when the monitor switch closes.
2. The fuse M8A also blows when asymmetric rectifier, H.V. rectifier, H.V. wire harness, H.V.capacitor, magnetron or secondary winding of power transformer is shorted.
3. If the wire harness or electrical components are short-circuited, this fuse M8A blows to prevent an electric shock or fire hazard.
OVEN THERMAL CUT-OUT
The thermal cut-out, located on the top of the oven cavity, is designed to prevent damage to the oven by fire. If the foods load is overcooked, by either error in cook time or defect in the control unit, the thermal cut-out will open. 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 new one.
1. The fuse M8A blows when the contacts (COM-NO) of the 1st. latch switch and 2nd. latch switch remain closed with the oven door open and when the monitor switch closes.
2. The fuse M8A also blows when asymmetric rectifier, H.V. rectifier, H.V. wire harness, H.V.capacitor, magnetron or secondary winding of power transformer is shorted.
3. If the wire harness or electrical components are short-circuited, this fuse M8A blows to prevent an electric shock or fire hazard.
OVEN THERMAL CUT-OUT
The thermal cut-out, located on the top of the oven cavity, is designed to prevent damage to the oven by fire. If the foods load is overcooked, by either error in cook time or defect in the control unit, the thermal cut-out will open. 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 new one.
MAGNETRON
THERMAL CUT-OUT
The thermal cut-out located near the magnetron is designed to prevent damage to the magnetron if an over heated condition develops in the tube due to cooling fan failure, obstructed air guide, dirty or blocked air intake, etc. Under normal operation, the thermal cut-out remains closed. However, when abnormally high temperatures are reached within the magnetron, the thermal cut-out will open at 95˚C causing the oven to shut down, when the magnetron has cooled to 75˚C, the thermal cut-out closes and cook cycle will resume.
TURNTABLE MOTOR
The turntable motor drives the turntable roller assembly to rotate the turntable.
The thermal cut-out located near the magnetron is designed to prevent damage to the magnetron if an over heated condition develops in the tube due to cooling fan failure, obstructed air guide, dirty or blocked air intake, etc. Under normal operation, the thermal cut-out remains closed. However, when abnormally high temperatures are reached within the magnetron, the thermal cut-out will open at 95˚C causing the oven to shut down, when the magnetron has cooled to 75˚C, the thermal cut-out closes and cook cycle will resume.
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 is channeled through the oven cavity to remove steam and vapors given off from the heating foods. It is then exhausted through the exhausting air vents at the oven cavity
NOISE FILTER
The noise filter prevents the radio frequency interference that might flow back in the power circuit.
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 channeled through the oven cavity to remove steam and vapors given off from the heating foods. It is then exhausted through the exhausting air vents at the oven cavity
NOISE FILTER
The noise filter prevents the radio frequency interference that might flow back in the power circuit.
