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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.
20
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