R-7N76(W)M
R-7N76(B)M
4
OPERATION SEQUENCE
OFF CONDITION
Closing the oven door activates all door interlock switches
(1st. latch switch, 2nd. latch switch and stop switch.)
IMPORTANT:
When the oven door is closed, the contacts COM-NC of the
monitor switch must be open. When the microwave oven is
pluged in a wall outlet (240V / 50Hz), 240 volts A.C. is
supplied to the point H1 + H3 in the control unit.
Figure O-1 on page 35
1. The display flashes "88:88"
2. To set any programmes or set the clock, you must first
touch the STOP / CLEAR pad.
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 touching Time pad and
start the oven with touching START pad.
Function sequence Figure O-2 on page 35
CONNECTED COMPONENTS
RELAY
Oven lamp, Fan motor, Turntable motor
RY1
High voltage transformer
RY1 + RY2
Fan motor
RY6
1. 240 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)
1st latch Switch
COM-NO
Closed
Opened
Monitor Switch
COM-NC
Opened
Closed
2nd latch switch
COM-NO
Closed
Opened
Stop switch
COM-NO
Closed
Opened
The circuit to the high voltage transformer and turntable
motor are cut off when the 1st latch switch, 2nd. latch switch
and stop switch are made open. The circuit to the fan motor
is cut off when the relay RY6 is 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 stay
closed. Shown in the display is remaining time.
6. MONITOR SWITCH CIRCUIT
The monitor switch is mechanically controlled by the
oven door, and monitors the operation of the 1st latch
switch.
6-1. When the oven door is opened during or after the cycle
of a cooking program, the 1st latch switch and stop
switch must open their contacts (COM-NO) first. After
that the contacts (COM-NC) of the monitor switch can
be closed and the contacts of stop switch can be
opened.
6-2. When the oven door is closed, the contacts (COM-NC)
of the monitor switch must be opened first, and the
contacts (COM-NO) of 2nd. latch switch must be closed.
After that the contacts of the 1st latch switch and the
stop switch are closed.
6-3. When the oven door is opened and the contacts of the
1st latch switch remain closed, the fuse M8A will blow,
because the monitor switch are 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 240 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 micro-
wave power are given.
CONVECTION COOKING CONDITION
PRE-HEATING CONDITION (Figure O-3)
Program desired convection temperature by touching CON-
VECTION pad.
When the START pad is touched, the following operations
occur:
1. The coil of shut-off relays RY1,RY4 and RY6 are
energized, the oven lamp, cooling fan motor, turntable
motor and convection motor are turned on.
2. The coil of shut-off relay RY3 is energized by the control
unit and the main supply voltage is added to the convection
heating element.
3. When the oven temperature reaches the selected pre-
30 sec. ON
24 sec. ON
18 sec. ON
12 sec. ON
6 sec. ON
8 sec. OFF
14 sec. OFF
20 sec. OFF
28sec. 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.
2 seconds are needed for heating up the magnetron
filament.
