OPERATION
DESCRIPTION OF OPERATING SEQUENCE
The following is a complete description of component
functions during the two stages of oven operation.
OFF CONDITION
Closing the door activates both door latch switches: upper
latch switch and lower latch switch. (In this condition, the
monitor switch is opened).
The stop switch on the control panel is activated by the door
lever.
When oven is plugged in, the 240 volts A.C. is supplied to the
control unit. But no components in the oven will operate,
(Figure 1.)
Note: When the door is opened by pushing the door open
button, the oven lamps come on.
1. The display, will show a flashing “88:88” and ail indicators
will light.
To set any program or set the clock, you must first touch
the CLEAR pad.
This will cancel “88:88” and all in-
dicators, and 1:OO will appear on the display and count
up every one minute.
COOKING CONDITION
1. HIGH COOKING
Program desired cooking time and Variable Cooking Con-
trol by touching the NUMBER pads and the HIGH pad of
the Variable Cooking Control.
When the START pad is touched, the following operations
occur: (Figure 21
5-t The COOK and HIGH indicators light.
The numbers of the digital readout start counting
down to zero.
4 -2
The coii of control relay (RL2) is energized.
A. The relay contacts (A) close to provide a current
path to the oven lamps.
B. The relay contacts (B) close to provide a current
oath to the turntable motor and fan motor.
f-3 The coil of cook relay (R Ll ) is energized.
The relay contacts close to provide a current path to
the power transformer.
14
The 240 volts A.C. is supplied to the primary winding
of the power transformer and is converted to 3.45
volts A.C. output on the filament winding, and ap-
proximately 2350 volts A.C on the high voltage wind-
ing.
l-5 The 3.45 volts A.C. output from filament winding
heats the magnetron filament.
l-6 The 2350 volts A.C. output from the high voltage
winding of the power transformer is sent to a voltage
doubler circuit consisting of a high voltage capacitor
and a rectifier.
The 2350 volts A.C. is converted to approximately
4900 negative D.C. voltage (peak to peak) by the
voltage doubler circuit and sent to the magnetron
tube assembly .
1-7 The negative 4000 volts D.C. is applied to the
cathode of the magnetron tube. This causes the
magnetron to oscillate and produce the 2450 MHz
cooking frequency.
1-8 The RF energy produced by the magnetron tube is
channeled through the waveguide into the cavity
feed-box, and then into the cavity where the food is
placed to be cooked.
l-9 Upon completion of the cooking time, the follow-
ing results will occur:
A. The control relay (RL2) will be de-energized,
de-energizing the oven lamps, fan motor and
turntable motor.
8. The cook relay (RLl ) will be de-energized,
opening the circuit to the power transformer
stopping the generation of microwave energy by
the magnetron.
C. The COOK and HIGH indicators will go out,
and the time of day will reappear.
D. The end of cooking signal will sound, and the
oven will revert OFF condition.
l-1 0 When the door is opened .during a cook cycle, the
latch switches, the stop switch and the monitor
switch are activated with the following results. The
circuits to the turntable motor, the fan motor, and
the high voltage components are deenergized, the
oven lamps remains on, and the digital readout dis-
piays the time still remaining in the cook cycle
when the door was opened.
l-l ? The monitor switch is electrically monitoring the
operation of the upper and lower latch switches and
is mechanically assocrated with the door so that it
will function in the following sequence.
(1 1 When the door opens from closed position, the
upper and lower latch switches first operate to
open their contacts, and then the monitor switch
contacts close.
(2) When th
e
d
oor is ciosed from open position, the
monitor switch contacts first open, and then the
contacts of the upper and lower latch switches
ciose.
In case the upoer and lower iatch switches both fail with their
contacts ciosed when the door is opened, closing of the moni-
tor switch contacts will form a short circuit through the fuse,
upper latch switch and lower latch switch, causing the fuse to
blow.
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