Operation; Operating Sequence - Sharp R-312AW Service Manual

R-312AW
R-312AK
The following is a description of component functions during
oven operation.
OFF CONDITION
Closing the door activates door sensing switch, primary
interlock switch and the third door switch. (In this condition,
the monitor switch contacts are opened.)
When oven is plugged in, 120 volts A.C. is supplied to the
noise filter and 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
and program the power level by touching the POWER
LEVEL pad and Number 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 3.2 volts
A.C. output on the filament winding, and approximately
2150 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
channeled 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, monitor
switch, door sensing switch, primary interlock switch and
third door switch are activated with the following results.
The circuits to the turntable motor, the cooling fan motor,
and the high voltage components are de-energized, and
the digital readout displays the time still remaining in the
cook cycle when the door was opened.
7. The monitor switch is electrically monitoring the operation
of the primary interlock switch and it 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 third
door switch, primary interlock switch and door sensing
switch open their contacts, and then the monitor switch
contacts close.

OPERATION

DESCRIPTION OF OPERATING SEQUENCE
(2) When the door is closed from the open position, the
monitor switch contacts first open, and then the contacts
of the primary interlock switch, door sensing switch and
third door switch close.
If the primary interlock switch fails with their contacts closed
when the door is opened, the closing of the monitor switch
contacts will form a short circuit through the monitor fuse
and primary interlock switch causing the monitor 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 an interval second time base. Micro-
wave power operation is as follows:
VARI-MODE ON TIME
Power 10(P-HI)
(100% power)
Power 9(P-90)
(approx. 90% power)
Power 8(P-80)
(approx. 80% power)
Power 7(P-70)
(approx. 70% power)
Power 6(P-60)
(approx. 60% power)
Power 5(P-50)
(approx. 50% power)
Power 4(P-40)
(approx. 40% power)
Power 3(P-30)
(approx. 30% power)
Power 2(P-20)
(approx. 20% power)
Power 1(P-10)
(approx. 10% power)
Power 0(P-0)
(0% power)
Note: The ON/OFF time ratio does not correspond with
the percentage of microwave power, because
approx. 2 seconds are needed for heating of the
magnetron filament.
6
OFF TIME
32 sec. 0 sec.
30 sec. 2 sec.
26 sec. 6 sec.
24 sec. 8 sec.
22 sec. 10 sec.
18 sec. 14 sec.
16 sec. 16 sec.
12 sec. 20 sec.
8 sec. 24 sec.
6 sec. 26 sec.
0 sec. 32 sec.