Sharp Carousel R-3S56 Service Manual - Page 6
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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.
Figure O-1 on page 25
1. The display shows " 0".
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 with the touching Time key and
start the oven with touching START key.
Function sequence
Figure O-2 on page 25
CONNECTED COMPONENTS
Oven lamp, Fan motor, Turntable motor
Power transformer
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 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 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.
SWITCH
CONTACT
1st. latch switches COM-NO
2nd. latch switch
COM-NO
Monitor switch
COM-NC
Stop switch
COM-NO
OPERATION SEQUENCE
RELAY
RY1
RY2
CONDITION
DURING
DOOR OPEN
COOKING
(NO COOKING)
Closed
Open
Closed
Open
Open
Closed
Closed
Open
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.
6. MONITOR SWITCH CIRCUIT
The monitor switch is mechanically controlled by oven
door, and monitors the operation of the 1st and 2nd. latch
switches.
6-1 When the oven door is opened during or after the cycle
of a cooking program, the 1st. latch and 2nd. latch
switch must open their contacts first.
After that the contacts (COM-NC) of the monitor switch
can be closed.
6-2. When the oven door is closed, the contacts (COM-NC)
of the monitor switch must be opened. After that the
contacts of the 1st. latch, 2nd. latch and stop switch are
closed and the contacts (COM-NO) of the stop switch
can be opened.
6-3. When the oven door is opened and the contacts of the
1st and 2nd latch switches remain closed. The fuse
M6.3A 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, rated voltage 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.
SETTING;
32 sec. ON
HIGH
24 sec. ON
MEDIUM HIGH
18 sec. ON
MEDIUM
12 sec. ON
MEDIUM LOW
6 sec. ON
LOW
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.
4
8 sec. OFF
Approx. 70%
14 sec. OFF
Approx. 50%
20 sec. OFF
Approx. 30%
26 sec. OFF
Approx. 10%