7
R-733 -
OFF CONDITION
Closing the door activates all door interlock switches
(monitored 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
(230V 50Hz), the line voltage is supplied to the point
A1+A3 in the control unit.
Figure O-1 on page 28
1. The display flashes "88:88”.
2. To set any programmes or set the clock, you must first
touch the STOP pad.
3. “:” appears in the display.
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 ROTARY knob and
start the oven by touching START button.
Function sequence Figure O-2 on page 28
CONDITION
DURING
DOOR OPEN
SWITCH
CONTACT
COOKING
(NO COOKING)
Monitored latch switch
COM-NO
Closed
Open
Monitor switch
COM-NC
Open
Closed
COM-NO
Closed
Open
Stop switch
COM-NO
Closed
Open
The circuits to the power transformer, fan motor and
turntable motor are cut off when the primary 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 SW2 is mechanically controlled by
oven door, and monitors the operation of the
monitored latch switch SW1
6-1
When the oven door is open during or after the
cycle of cooking program, the monitored latch and
stop switches SW1 + SW3 must open their contacts
first. After that the contacts (COM - NC) of the
monitor switch SW2 can be closed.
6-2
When the oven door is closed, the contacts
(COM - NC) of the monitor switch SW2 must be
opened. After that contacts of the monitored latch
and stop switches SW1 + SW3 are closed.
6-3
When the oven door is opened and the contacts of
the monitored latch switch SW1 remain closed, the
fuse F8A 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, the line voltage is supplied to the power
transformer intermittently within a 48-second time base
through the relay contact which is coupled with the
current-limiting relay RY3. The following levels of
microwave power are given.
SETTING
NOTE: The ON/OFF time ratio does not exactly
correspond to the percentage of microwave
power, because approx. 3 seconds are needed
for heating up the magnetron filament.
CONNECTED COMPONENTS
RELAY
Oven lamp, Fan motor, Turntable motor
RY1
Grill heater
RY2
Power transformer
RY3
1. The line 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 single tone is heard
and the relays RY1 + RY3 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.
OPERATING SEQUENCE
48 sec. ON
36 sec. ON
26 sec. ON
16 sec. ON
8 sec. ON
12 sec. OFF
22 sec. OFF
32 sec. OFF
40 sec. OFF
HIGH
MEDIUM
HIGH
MEDIUM
MEDIUM
LOW
LOW
Approx. 70% = 630Watts
Approx. 50% = 450Watts
Approx. 30% = 270Watts
Approx. 10% = 90Watts
Approx100% = 900Watts