Operation - Sharp R-9360 Service Manual

R-9360
OPERATION
DESCRIPTION OF OPERATING SEQUENCE
The following is a complete description of component func-
tions during oven operation.
OFF CONDITION
Closing the door activates both door interlock switches; low-
er latch switch and upper latch switch.
(In this condition, the monitor switch contacts are opened)
The stop switch is activated (contacis closed) by the lower
latch head, when the door is closed.
When oven is plugged in, the power supply voltage is added
to the control unit. But no components in the oven will oper-
ate, (Figure O-l)
-.
Note: When the door is opened by pushing the door open but-
ton, the oven lamp comes on.
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 1:OO will
appear and count up every 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 COOK (or START) pad is touched, the following
operations occur:
l-l.
1-2.
l-3.
1-4.
1-5.
1-6.
1-7.
1-8.
The power transformer, oven lamp, etc. are turned on.
(For details, refer to Figure O-2.)
The power supply voltage is added to the primary
winding of the power transformer and is converted
to about 3 volts A.C. output on the filament winding,
and approximately 2300 volts A.C on the high vol-
tage winding.
About 3 volts A.C. output from the filament winding
heats the megnetron filament.
The 2300 volts A.C. is converted to approximately
4000 negative D.C. volts by the voltage doubler cir-
cuit consisting of a H.V. capacitor and rectifier and
sent to the magnetron cathode.
This causes the magnetron to oscillate and produce
the 2450 MHz cooking frequency.
This RF energy is channeled through the waveguide
into the cavity feed-box, and then into the cavity
where the food is placed to be cooked.
Upon completion of the cooking time, the power trans-
former, oven lamp, etc. are turned off, and the gener-
ation of microwave energy is stopped. The oven will
revert to the OFF condition.
When the door is opened during a cook cycle, the latch
switches, stop switch and monitor switch are activat-
ed with the following results. The circuits to the turnt-
able motor, the cooling fan motor, and the high voltage
components are deenergized, the oven lamp remains
on, and the digital readout displays the time still re-
maining in the cook cycle when the door was opened.
l-9. The monitor switch is electrically monitoring the oper-
ation of the upper latch switch and is mechanically
associated with the door so that it will function in the
following sequence.
(1) When the door opens from a closed position, the
upper latch switch opens their contacts, and then
the monitor switch contacts close.
(2) When the door is closed from the open position,
the monitor switch contacts first open, and then
the contacts of the upper latch switch closes.
If the upper latch switch fails with its contacts closed when
the door is opened, the closing of the monitor switch contacts
will form a short circuit through the fuse, temp. fuse, upper
latch switch, causing the monitor fuse to blow.
2. MED HIGH, MED, MED LOW or LOW COOKING.
When the Variable Cooking is programed, power supply vol-
tage is supplied to the power transformer intermittently
through the contacts of the cook relay which is operated
by the control unit within a 32 second time base.
The microwave power operation is as follows:
HIGH
ME0
HIGH
ME0
ME0
LOW
LOW
t-
ON
32 sec.
-8 sec.
m
24 sec.
OFF
ON
- 14 sec.
OFF
I
ON
20 sec.
12 sec.
OFF
I
6 sec.
MICROWAVE POWER
= 100%
MICROWAVE POWER
= Approx. 70%
MICROWAVE POWER
= Approx. 50%
MICROWAVE POWER
= Approx. 30%
MICROWAVE POWER
= Approx 10%
Note: The ON/OFF time ratio does not correspond with the per-
centage of microwave power, because approx. 2 se-
conds are needed for heating of the magnetron filament.
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