9
R-84ST -
OPERATION SEQUENCE
OFF CONDITION
Closing the oven door activates all door interlock switches
(Monitored latch switch and stop switch.
IMPORTANT:
When the oven door is closed, the contacts COM-NC of the
monitor switch SW2 must be open and the contacts (COM-
NO) must be closed. When the microwave oven is plugged
in a wall outlet (230V / 50Hz), 230 volts A.C. is supplied to
the point A1 + A3 in the control unit.
Figure O-1 on page 34
1. The display flashes "88:88"
2. To set any programmes or set the clock, you must first
touch the STOP key.
3. " : " appears in 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 Time keys and start
the oven by touching the START key.
Function sequence Figure O-2 on page 34
CONNECTED COMPONENTS
RELAY
Oven lamp, Turntable motor
RY1
High voltage transformer
RY2
Fan motor
RY6
1. 230 volts A.C. 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 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 + RY6 go back to their home
position. The circuits to the oven lamp, high voltage
transformer, fan motor and turntable motor are cut off.
5. When the oven door is opened during a cooking cycle,
the switches come to the following condition.
Switch
Contact
Condition
During
Oven Door
Cooking
Open(No cooking)
Monitored latch Switch COM-NO
Closed
Opened
Monitored latch Switch COM-NC
Opened
Closed
Monitor Switch
COM-NO
Closed
Opened
Monitor Switch
COM-NC
Opened
Closed
Stop switch
COM-NO
Closed
Opened
The circuit to the high voltage transformer, is cut off when
the contact of relay RY2 contacts COM-NO of the
monitored latch switch, and monitor switch SW2 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 are made open. The relays RY2 and RY5 are made
open when the door is opened. The oven lamp remains on
even if the oven door is opened after the cooking cycle has
been interrupted, because the relay RY1 stay closed.
Shown in the display is remaining time.
6. MONITOR SWITCH CIRCUIT
The monitor switch SW2 is mechanically controlled by
the oven door, and monitors the operation of the
monitored latch switch SW1.
6-1. When the oven door is opened during or after the
cycle of a cooking program, the monitored latch switch
SW1 and stop switch SW3 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 monitor switch SW2 are made
open.
6-2. When the oven door is closed. The contacts (COM-
NC) of the monitor switch SW2 must be opened and
the contacts (COM-NO) of monitor switch SW2 must
be closed. After that the contacts of the monitored
latch switch SW1 and the stop switch SW3 are made
closed.
6-3. When the oven door is opened and the contacts of the
monitored latch switch SW1 remain closed, the fuse
F2 F8A will blow. Because the relay RY1 and monitor
switch SW2 are closed and a short circuit is caused.
CONVECTION COOKING CONDITION
PREHEATING CONDITION (Figure O-4)
Program desired convection temperature by touching CON-
VECTION key. When the START key is touched, the following
operations occur:
1. The coil of shut-off relays RY1, RY6 and RY7 are energized,
the oven lamp, cooling fan motor, turntable motor and
convection motor are turned on.
2. The coil of shut-off relays RY3 and RY4 are energized by
the control unit and the main supply voltage is added to the
top and bottom heater.
3. When the oven temperature reaches the selected preheat
temperature, the following operations occur;
3-1. The shut-off relays RY3 and RY4 are de-energized by
the control unit temperature circuit and thermistor, opening
the circuit to the top and bottom heating elements.
3-2. The oven will continue to function for 30 minutes, turning
the convection heating elements on and off, as needed
to maintain the selected preheat temperature. The oven
will shut-down completely after 30 minutes.
MEDIUM HIGH, MEDIUM, MEDIUM LOW, LOW
COOKING
When the microwave oven is preset for variable cooking
power, the 230 volts A.C. power is supplied to the high voltage
transformer intermittently within a 32-second time base through
the relay contact which is coupled with the current-limiting
relay RY2. The following levels of microwave power are given.
32 sec. ON
24 sec. ON
18 sec. ON
12 sec. ON
6 sec. ON
8 sec. OFF
14 sec. OFF
20 sec. OFF
28 sec. OFF
HIGH
MEDIUM
HIGH
MEDIUM
MEDIUM
LOW
LOW
Approx. 70%
Approx. 50%
Approx. 30%
Approx. 10%
Approx. 100%
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.
