7
R-25AM
OPERATION SEQUENCE
4. When the cooking time is up, a signal tone is heard and
the relays RY3+RY4 go back to their home position.
The circuits to the high voltage transformers T1+T2.
The relay RY1 remains and oven lamp, blower motor
and antenna motors work for 1 minute.
5. When the door is opened during a cook cycle, the
switches come to the following condition.
CONDITION
DURING
DOOR OPEN
SWITCH
CONTACT
COOKING
(NO COOKING)
Interlock switches COM-NO
Closed
Open
Monitor switches
COM-NC
Open
Closed
Stop switch
COM-NO
Closed
Open
The circuits to the high voltage transformers T1+T2 are
cut off when the interlock and stop switches
SW1+SW2+SW5 are made open. The blower motor BM,
antenna motors and 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, but the program is
cancelled if the oven is not started within 1 minute.
6. MONITOR SWITCH CIRCUIT
The monitor switches SW3+SW4 are mechanically
controlled by oven door, and monitors the operation of
the interlock switches SW1+SW2.
6-1. When the oven door is opened during or after the
cycle of a cooking program, the interlock switches
SW1+SW2 and stop switches SW5 must open their
contacts first. After that the contacts (COM-NC) of the
monitor switches SW3+SW4 can be closed.
6-2. When the oven door is closed, the contacts (COM-
NC) of the monitor switches SW3+SW4 must be
opened first. After that the contacts (COM-NO) of the
interlock switches SW1+SW2 and stop switch SW5
must be closed.
6-3. When the oven door is opened and the contacts of the
interlock switch SW1 (or SW2) remain closed, re-
mains closed, the fuse F1 F10A (or F2 F10A) will
blow, because the monitor switch SW3 (or SW4) is
closed and a short circuit is caused.
MICROWAVE VARIABLE COOKING
When the microwave oven is preset for variable cooking
power, the line voltage is supplied to the high voltage
transformers T1+T2 intermittently within a 48 second time
base through the contacts of the relays RY3+RY4.
The following levels of microwaves power are given.
Closing the door activates all door interlock switches
(interlock switches 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 (230 volts, 50Hz), the line voltage
is supplied to the control unit through the noise filter.
Figure O-1 on page 3
4
1. The digital display shows .
0
IDLE CONDITION
When the door is opened, the contacts of the interlock
switches SW1+SW2 and stop switch SW5 open, initiating
the following:
Figure O-2 on page 34
1. A signal is input to the control unit energizing the coil of
shut-off relay RY-1.
2. The shut-off relay RY-1 contacts close completing
circuits to turn on the oven lamp, blower motor and
antenna motors.
3. If the door remains open, 60 seconds later the control
unit de-energizes shut-off relay RY-1 turning off the
oven lamp, blower motor and antenna motors.
When the door is closed, the contacts of the interlock switches
SW1+SW2 and stop switch SW5 close. With the closing of the
stop switch SW5 contacts, an additional circuit is provided which
will permit the operation of the oven when one of the touch pads
is depressed. Since the control is enabled through the stop
switch SW5, the door must be closed before the touch pads will
be effective. When the door is closed, a full 60 second IDLE
condition is always provided for selecting and pressing the
desired touch pads. A 60 second IDLE condition will also follow
the end of each cook cycle.
MICROWAVE COOKING CONDITION
Enter a desired cooking time by turning ELECTRONIC
TIMER knob. And then touch START button.
NOTE: The programme is canceled when any buttons
are not touched for more than 3 minutes dur-
ing programming.
Function sequence Figure O-3 on page 35
CONNECTED COMPONENTS
RELAY
Oven lamp/ Blower motor/ Antenna motors
RY1
High voltage transformer T1
RY3
High voltage transformer T2
RY4
1. The line voltage is supplied to the primary winding of
the two high voltage transformers. 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 magnet-
ron 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.
NOTE: The ON/OFF time ratio does not exactly corre-
spond to the percentage of microwave power,
because approx. 3 seconds are needed for heat-
ing up the magnetron filament.
48 sec. ON
10%
26 sec. ON
50%
12 sec. ON
20%
8 sec. ON
10%
