R- 308JK
R - 308JS
R-308JW
R-309JW
6
OPERATION
DESCRIPTION OF OPERATING SEQUENCE
The following is a description of component functions during
oven operation.
OFF CONDITION
Closing the door activates the door sensing switch and second-
ary interlock switch. (In this condition, the monitor switch
contacts are opened.)
When oven is plugged in, 120 volts A.C. is supplied to the
control unit. (Figure O-1).
1. The display will show flashing "
88:88
".
To set any program or set the clock, you must first touch
the STOP/CLEAR pad. The display will clear, and " : " will
appear.
COOKING CONDITION
Program desired cooking time by touching the NUMBER pads.
Program the power level by touching the POWER LEVEL pad.
When the START pad is touched, the following operations
occur:
1. The contacts of relays are closed and components connected
to the relays are turned on as follows.
(For details, refer to Figure O-2)
RELAY
CONNECTED COMPONENTS
RY-1
oven lamp/turntable motor/fan motor
RY-2
power transformer
2. 120 volts A.C. is supplied to the primary winding of the
power transformer and is converted to about 3.3 volts A.C.
output on the filament winding, and approximately 2360
volts A.C. on the high voltage winding.
3. The filament winding voltage heats the magnetron filament
and the H.V. winding voltage is sent to a voltage doubler
circuit.
4. The microwave energy produced by the magnetron is
channelled through the waveguide into the cavity feed-box,
and then into the cavity where the food is placed to be
cooked.
5. Upon completion of the cooking time, the power transformer,
oven lamp, etc. are turned off, and the generation of
microwave energy is stopped. The oven will revert to the
OFF condition.
6. When the door is opened during a cook cycle, the monitor
switch, door sensing switch, secondary interlock switch,
relay (RY1) and primary interlock relay are activated with
the following results. The circuits to the turntable motor, the
cooling fan motor, and the high voltage components are de-
energized, the oven lamp remains on, and the digital read-
out displays the time still remaining in the cook cycle when
the door was opened.
7. The monitor switch electrically monitors the operation of the
secondary interlock switch and primary interlock relay and
is mechanically associated with the door so that it will
function in the following sequence.
(1) When the door opens from the closed position, the primary
interlock relay (RY2) and secondary interlock switch open
their contacts. And contacts of the relay (RY1) remains
closed. Then the monitor switch contacts close.
(2) When the door is closed from the open position, the monitor
switch contacts open first. Then the contacts of the secondary
interlock switch and door sensing switch close. And contacts
of the relay (RY1) open.
If the secondary interlock switch and primary interlock relay
(RY2) fail with the contacts closed when the door is opened, the
closing of the monitor switch contacts will form a short circuit
through the C/T fuse, secondary interlock switch, relay (RY1)
and primary interlock relay (RY2), causing the C/T fuse to blow.
POWER LEVEL P-0 TO P-90 COOKING
When Variable Cooking Power is programmed, the 120 volts
A.C. is supplied to the power transformer intermittently through
the contacts of relay (RY-2) which is operated by the control
unit within a 32 second time base. Microwave power operation
is as follows:
VARI-MODE
ON TIME
OFF TIME
P-HI (100% power)
32 sec.
0 sec.
P-90 (approx. 90% power)
30 sec.
2 sec.
P-80 (approx. 80% power)
26 sec.
6 sec.
P-70 (approx. 70% power)
24 sec.
8 sec.
P-60 (approx. 60% power)
22 sec.
10 sec.
P-50 (approx. 50% power)
18 sec.
14 sec.
P-40 (approx. 40% power)
16 sec.
16 sec.
P-30 (approx. 30% power)
12 sec.
20 sec.
P-20 (approx. 20% power)
8 sec.
24 sec.
P-10 (approx. 10% power)
6 sec.
26 sec.
P-0 (approx. 0% power)
0 sec.
32 sec.
Note:
The ON/OFF time ratio does not correspond with
the percentage of microwave power, because
approx. 3 seconds are needed for heating of the
magnetron filament.
POWER OUTPUT REDUCTION
If the oven is set for more than 20 minutes at 80, 90 or 100%
power level, after the first 20 minutes the power level will
automatically adjust itself to 70% power to avoid overcooking.
