Operation Sequence - Sharp R-937 Service Manual

OFF CONDITION
Closing the door activates the monitored latch switch and
the stop switch.
IMPORTANT:
When the oven door is closed, the contacts COM-NC
of the monitor switch must be open. When the micro-
wave oven is plugged in a wall outlet (230V / 50Hz), the
line voltage is supplied to the noise filter.
Figure O-1 on page 33
1. The control unit is not energized. The display shows
nothing (Fig. O-1 (a)).
2. Open the door. The contacts (COM-NC) of the monitored
latch switch are closed and the control unit is energized.
Then contacts of relays RY1 and RY5 are closed, and
the oven lamp will light and the display will show "SE-
LECT LANGUAGE" in 5 languages. (Fig. O-1(b)).
NOTE: Once the language is selected using the LAN-
GUAGE button, the display will show "ENERGY
SAVE MODE TO GO OUT OF ENERGY SAVE
MODE SET CLOCK" when the oven is plugged in.
3. Close the door. The contacts (COM-NC) of the moni-
tored latch switch are opened and the contacts of relay
RY1 are opened and the oven lamp will be turned off.
The display will show " . 0". (Fig. O-1(c)).
NOTE: Energy save mode
1. If the oven has not been used for more than 3 minutes,
the contacts of the relay RY5 will be opened and the
control unit will be not energized. Open and close the
door, the control unit will resume.
2. If the clock is set, this energy save mode does not work.
3. If the display shows different messages from ENERGY
SAVE MODE, the oven may be set in demo mode. Close
the door, see operation manual to cancel demo mode.
MICROWAVE COOKING CONDITION
HIGH COOKING
Rotate the COOKING MODE dial to the
And press the POWER LEVEL button once. And enter the
cooking time by rotating the TIME/WEIGHT dial. And start
the oven by pressing START button.
Function sequence Figure O-2 on page 34
CONNECTED COMPONENTS
Oven lamp, Turntable motor
High voltage transformer
Fan motor
1. 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.
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 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.
4. When the cooking time is up, a signal tone is heard and
the relays RY1 + RY2 + RY6 go back to their home
position. The circuits to the oven lamp, high voltage

OPERATION SEQUENCE

5. When the oven door is opened during a cooking cycle,
Switch
Monitored latch switch
Stop switch
Monitor Switch
The circuit to the high voltage transformer is cut off when
the contacts of relay RY2, and the contacts (COM-NO) of
the monitored latch switch SW1 and monitor switch SW3
are made open. The circuit to the fan motor is cut off when
the relay RY6 is made open. The circuit to the turntable
motor is cut off when the contacts (COM-NO) of the
monitored latch 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.
6. MONITOR SWITCH CIRCUIT
6-1. When the oven door is opened during or after the
6-2. When the oven door is closed, the contacts (COM-
micro setting.
6-3. When the oven door is opened and the contacts
RELAY
RY1
RY2
MEDIUM HIGH, MEDIUM, MEDIUM LOW, LOW
RY6
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.
100% (HIGH)
70%(MEDIUM
50%(MEDIUM)
30% (MEDIUM
7
transformer, fan motor and turntable motor are cut off.
the switches come to the following condition.
Contact
COM-NO
COM-NC
COM-NO
COM-NO
COM-NC
The monitor switch SW3 is mechanically controlled
by the oven door, and monitors the operation of the
monitored latch switch SW1.
cycle of a cooking program, the monitored latch
switch SW1 and stop switch SW2 must open their
contacts (COM-NO) first. And the contacts (COM-
NC) of the monitored latch switch SW1 are made
closed. After that the contacts (COM-NC) of the
monitor switch SW3 can be closed and the contacts
(COM-NO) of monitor switch SW3 are made open.
NC) of the monitor switch SW3 must be opened and
the contacts (COM-NO) of monitor switch SW3 must
be closed. After that the contacts (COM-NO) of the
monitored latch switch SW1 and the stop switch SW2
are made closed. And the contacts (COM-NC) of the
monitored latch switch SW1 are made open.
(COM-NO) of the monitored latch switch SW1 remain
closed, the fuse F2 F8A will blow. Because the relay
RY1 and monitor switch SW3 are closed and a short
circuit is caused.
32 sec. ON
24 sec. ON
HIGH)
18 sec. ON
12 sec. ON
LOW)
6 sec. ON
10%(LOW)
Condition
During Oven Door
Cooking Open(No cooking)
Closed Opened
Opened Closed
Closed Opened
Closed Opened
Opened Closed
100%
8 sec. OFF
Approx. 70%
14 sec. OFF
Approx. 50%
20 sec. OFF
Approx. 30%
26 sec. OFF
Approx. 10%