Sharp R-8320E, Service Manual

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DESCRIPTION OF OPERATING SEQUENCE
(South Africa Model)
The following is a complete description of component
function during the three stages of oven operation.
OFF CONDITION
Closing the door activates both door latch switches:
upper latch switch and lower latch switch.
The stop switch on the control panel is activated by the
door lever.
When oven is plugged in, the 220 volts A.C. is supplied to
the transformer on the relay unit, and the transformer is
energized. But no components in the oven will operate
except damper motor which will run until the damper is
fully open. (Figure 4)
1. A display will show a flashing
To set any program or set the clock, you must first
touch the “CLEAR” pad. This will cancel and
will appear on the display and count up every one
minute.
2. A signal is input to the control unit, energizing the coil
of shut-off relay (RY4).
RY4 contacts close, completing a circuit to the damper
motor.
The damper motor now operates moving the damper to
the open position, thereby closing the contacts of the
damper switch which inputs a signal to the control
unit.
The coil of shut-off relay is de-energized, open-
ing its contacts, thereby turning off the damper motor.
Note:
When the door is opened by pushing the door
open button, the oven
and cooling fan
motor come on.
MICROWAVE COOKING CONDITION
1. HIGH COOKING
Program desired cooking time and Variable Cooking
Control by touching the NUMBER pads and the
“HIGH” pad of the Variable Cooking Control.
When the “COOK” pad is touched, the following
operations occur: (Figure 5)
The COOK and HIGH indicators light.
The numbers of the digital readout start counting
down to zero.
l-2 The coil of shut-off relay (RY2) 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 path to the turntable motor.
The coil of shut-off relay (RY3) is energized.
The relay contacts close to provide a current
path to the cooling fan motor.
The coil of cook relay is energized by the con-
trol unit and relay unit.
The relay contacts close to provide a current
path to the power transformer.
l-5 The 220 volts A.C. is supplied to the primary
winding of the power transformer and is con-
verted to 3.15 volts A.C. output on the filament
winding.
l-6 The 3.15 volts A.C. output from filament wind-
ing heats the magnetron filament.
1-7 The 2400 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 2400 volts A.C. is converted to approximate-
ly 4000 negative D.C. voltage (peak to peak) by
the voltage doubler circuit and sent to the
magnetron tube assembly.
l-8 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.
l-9 The RF energy produced by the magnetron tube
is channeled through the waveguide into the
cavity
and then into the cavity where
the food is placed to be cooked.
l-10 Upon completion of the cooking time, the
following results will occur:
A.
B.
C.
D.
E.
The shut-off relay (RY2) will be de-ener-
gized, de-energizing the oven lamps and the
turntable motor.
The shut-off relay (RY3) will be de-ener-
gized, de-energizing the cooling fan motor.
The cook relay will be de-energized, opening
the circuit to the power transformer stop-
ping the generation of microwave energy by
the magnetron.
The COOK and HIGH indicators will go out,
and the time of day will reappear.
The end of cooking signal will sound, and
the oven will revert OFF condition.
H I G H , M E D I U M o r M E D I U M L O W /
DEFROST- COOKING
Program disired cooking time by touching the number
pad or pads and “MED HIGH”, “MED” or “MED LOW/
DEFROST” pad of variable cooking control.
When the “COOK” pad is touched, the following
operations occur:
2-l.
The shut-off relays (RY2 and and cook relay
are energized.
2-2. The COOK and selected Variable Cooking
Control indicators light.
2-3. The 220 volts A.C. is supplied to the power
transformer intermittently through the cook
relay contacts which is operated by the control
unit within a 32 second time base.
The microwave power operation is as follows:
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