Read Sharp R-90GCK (serv.man17) Service Manual online
4
R-90GCK
OPERATION
DESCRIPTION OF OPERATING SEQUENCE
The following is a description of component functions
during oven operation.
during oven operation.
OFF CONDITION
Closing the door activates the door sensing switch and
secondary interlock switch and 3rd. latch switch. (In this
condition, the monitor switch contacts are opened.)
secondary interlock switch and 3rd. latch switch. (In this
condition, the monitor switch contacts are opened.)
IMPORTANT:
When the oven door is closed, the contacts COM-NC
of the monitor switch must be open. When the
microwave oven is plugged in a wall outlet (230 - 240V
/ 50Hz), the line voltage is supplied to the noise filter.
When the oven door is closed, the contacts COM-NC
of the monitor switch must be open. When the
microwave oven is plugged in a wall outlet (230 - 240V
/ 50Hz), the line voltage is supplied to the noise filter.
Figure O-1 on page 32
1. The display will show "PRESS STOP".
To set any program or set the clock, you must first touch
the STOP/CLEAR pad. The display will clear, and
" . 0 " will appear.
the STOP/CLEAR pad. The display will clear, and
" . 0 " will appear.
NOTE: When the door is opened, the oven lamp comes
on.
2. A signal is input to the control unit, energizing the coil
of shut-off relay (RY-4). RY4 contacts close, completing
a circuit to the damper motor. The damper motor now
operates moving the damper to the open position,
thereby closing the contacts of the damper switch
inputs a signal to the control unit. The coil of relay RY-
4 is de-energized, opening its contacts, thereby turning
off the damper motor.
a circuit to the damper motor. The damper motor now
operates moving the damper to the open position,
thereby closing the contacts of the damper switch
inputs a signal to the control unit. The coil of relay RY-
4 is de-energized, opening its contacts, thereby turning
off the damper motor.
MICROWAVE COOKING CONDITION
HIGH COOKING
Program desired cooking time by touching the TIME keys.
When the START pad is touched, the following operations
occur:
Program desired cooking time by touching the TIME keys.
When the START pad is touched, the following operations
occur:
1. The contacts of relays are closed and components
connected to the relays are turned on as follows.
(For details, refer to Figure O-2)
(For details, refer to Figure O-2)
RELAY
CONNECTED COMPONENTS
RY-1
Oven lamp/Turntable motor
RY-2
High voltage transformer
RY-3
Convection motor
RY-4
Damper motor
RY-5
Fan motor
RY-6
Convection motor
2. 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.
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.
3. 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..
sent to the voltage doubling circuit, where it is doubled
to negative voltage of approximately 4000 volts D.C..
4. 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.
energy is channelled through the waveguide (transport
channel) into the oven cavity, where the food is placed
to be cooked.
5. When the cooking time is up, a signal tone is heard and
the relays RY1 + RY2 + RY5 go back to their home
position. The circuits to the oven lamp, high voltage
transformer, fan motor and turntable motor are cut off.
position. The circuits to the oven lamp, high voltage
transformer, fan motor and turntable motor are cut off.
6. When the oven door is opened during a cooking cycle,
the switches come to the following condition.
Switch
Contact
Condition
During
During
Oven Door
Cooking
Open(No cooking)
Secondary interlock
switch
switch
COM-NO
Closed
Opened
Door sensing switch
COM-NO
Closed
Opened
3rd. latch switch
COM-NO
Closed
Opened
Monitor Switch
COM-NC
Opened
Closed
The circuit to the high voltage transformer is cut off
when the contacts of relay RY2, and the contacts
(COM-NO) of the secondary interlock switch are made
open. The circuit to the fan motor is cut off when the
relay RY5 is made open. The circuit to the turntable
motor is cut off when the contacts (COM-NO) of the
secondary interlock 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
remaining time.
when the contacts of relay RY2, and the contacts
(COM-NO) of the secondary interlock switch are made
open. The circuit to the fan motor is cut off when the
relay RY5 is made open. The circuit to the turntable
motor is cut off when the contacts (COM-NO) of the
secondary interlock 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
remaining time.
7. MONITOR SWITCH CIRCUIT
The monitor switch is mechanically controlled by the
oven door, and monitors the operation of the secondary
interlock switch and the relay RY2.
oven door, and monitors the operation of the secondary
interlock switch and the relay RY2.
7-1. When the oven door is opened during or after the
cycle of a cooking program, the secondary interlock
switch and the door sensing switch must open their
contacts (COM-NO) first. After that the contacts
(COM-NC) of the monitor switch can be closed and
the contacts (COM-NO) of 3rd. latch switch are made
open.
switch and the door sensing switch must open their
contacts (COM-NO) first. After that the contacts
(COM-NC) of the monitor switch can be closed and
the contacts (COM-NO) of 3rd. latch switch are made
open.
7-2. When the oven door is closed, the contacts (COM-
NC) of the monitor switch must be opened and the
contacts (COM-NO) of 3rd. latch switch must be
closed. After that the contacts (COM-NO) of the
secondary interlock switch and the door sensing
switch are made closed.
contacts (COM-NO) of 3rd. latch switch must be
closed. After that the contacts (COM-NO) of the
secondary interlock switch and the door sensing
switch are made closed.
7-3. When the oven door is opened and the contacts
(COM-NO) of the secondary interlock switch remain
closed, the fuse F10A will blow. Because the relay
RY2 and monitor switch are closed and a short circuit
is caused.
closed, the fuse F10A will blow. Because the relay
RY2 and monitor switch are closed and a short circuit
is caused.
MEDIUM HIGH, MEDIUM, MEDIUM LOW, LOW
COOKING
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 cur-
rent-limiting relay RY2. The following levels of microwave
power are given.
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 cur-
rent-limiting relay RY2. The following levels of microwave
power are given.
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