Operation Sequence - Sharp R-90GCH Service Manual

The following is a description of component functions
during oven operation.
OFF CONDITION
Closing the door activates the door sensing switch SW4
and secondary interlock switch SW1 and 3rd. latch switch
SW3. (In this condition, the monitor switch SW2 contacts
are opened.)
IMPORTANT:
When the oven door is closed, the contacts COM-NC
of the monitor switch SW2 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 on page 37
1. The display will show "SELECT LANGUAGE" in 3
languages.
To set any program or set the clock, you must first touch
the STOP key. The display will clear, and
" . 0 " will appear.
NOTE: When the door is opened, the oven lamp comes on.
Once you select the language using the LANGUAGE
key, the display will show "PRESS STOP" when
you plug the oven in.
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 SW5
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)+1min key 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)
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
SSR1 Top heating element
SSR2 Side heating element
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.
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
OPERATION
DESCRIPTION OF OPERATING SEQUENCE
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.
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.
6. When the oven door is opened during a cooking cycle,
the switches come to the following condition.
Switch Contact
Secondary interlock
COM-NO
switch
Door sensing switch SW4
3rd. latch switch SW3 COM-NO
Monitor switch SW2 COM-NC
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 SW1 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 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
remaining time.
7. MONITOR SWITCH CIRCUIT
The monitor switch SW2 is mechanically controlled by
the oven door, and monitors the operation of the
secondary interlock switch SW1 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 SW1 and the door sensing switch SW4 must
open their contacts (COM-NO) first. After that the
contacts (COM-NC) of the monitor switch SW2 can
be closed and the contacts (COM-NO) of 3rd. latch
switch SW3 are made open.
7-2. When the oven door is closed, the contacts (COM-
NC) of the monitor switch SW2 must be opened and
the contacts (COM-NO) of 3rd. latch switch SW3
must be closed. After that the contacts (COM-NO) of
the secondary interlock switch SW1 and the door
sensing switch SW4 are made closed.
7-3. When the oven door is opened and the contacts
(COM-NO) of the secondary interlock switch SW1
remain closed, the fuse F2 F10A will blow. Because
the relay RY2 and monitor switch SW2 are closed
and a short circuit is caused.
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 cur-
7
R-90GCH
Condition
During Oven Door
Cooking Open(No cooking)
Closed Opened
COM-NO Closed Opened
Closed Opened
Opened Closed