Operation Sequence - Sharp R-390B Service Manual

R-390B
OFF CONDITION
Closing the door activates 1st. latch switch, 2nd. latch
switch and stop switch. (In this condition, the monitor
switch contacts are opened.)
When the oven is plugged in, rated voltage is supplied to
the control unit.
Figure O-1 on page 26
1. The display will shows "VIEW VIDEO DEMO" and
"SET CLOCK/DATE".
2. Select "SET CLOCK/DATE" referring to the
operation manual.
NOTE: If any keys are not touched for 30 seconds, the
display will go on to the Video Demo mode. To
cancel the Video Demo mode, touch the STOP/
CLEAR key. And then set the clock.
3. The display will show the home page after setting the
clock.
4. The following is the example of the home page in the
case the time of the day is set to 4:50 p.m. on May 23rd.
4:50
EASY DEFROST >
INFORMATION >
NOTE: Even if the clock is not set, the display will show the
Home Page by touching the STOP/CLEAR key
within 30 seconds after plugged in.
MICROWAVE COOKING CONDITION
HIGH COOKING
Program desired cooking time by touching the NUMBER
keys. Program the power level by touching the CHANGE
POWER key until desired power level appears and start
the oven with touching START key.
Function sequence
Figure O-2 on page 26
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 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.

OPERATION SEQUENCE

MAY 23
PM
COOK >
REHEAT >
RELAY
RY1
RY2
5. When the door is opened during a cook cycle, the
switches come to the following condition.
SWITCH CONTACT
1st. latch switch COM-NO
2nd. latch switch COM-NO
Monitor switch COM-NC
Stop switch COM-NO
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 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.
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 switch, 2nd. latch switch
and stop switch are closed.
6-3. When the oven door is opened and the contacts of
the1st. 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 cur-
rent-limiting relay. The following levels of microwave power
are given.
SETTING;
HIGH
MEDIUM HIGH
MEDIUM
MEDIUM LOW
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
CONDITION
DURING DOOR OPEN
COOKING (NO COOKING)
Closed Open
Closed Open
Open Closed
Closed Open
32 sec. ON
8 sec. OFF
24 sec. ON
Approx. 70%
18 sec. ON 14 sec. OFF
Approx. 50%
12 sec. ON 20 sec. OFF
Approx. 30%
6 sec. ON 26 sec. OFF
Approx. 10%