Operation; Operating Sequence - Sharp R-370EK Service Manual

R- 370EK
R- 37 0ES
The following is a description of component functions during
oven operation.
OFF CONDITION
Closing the door activates the door sensing switch and
primary interlock switch. (In this condition, the monitor
switch contacts are opened.)
When oven is plugged in, 120 volts A.C. is supplied to the
control unit. (Figure O-1).
1. The display will show "SHARP SIMPLY THE BEST
PRESS CLEAR AND PRESS CLOCK".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. Program the power level by touching the POWER
LEVEL 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 3.4 volts
A.C. output on the filament winding, and approximately
2300 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
channelled 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, the
monitor switch, door sensing switch, primary interlock
switch, relay (RY1) and secondary interlock relay (RY2)
are activated with the following results. The circuits to the
turntable motor, the cooling fan motors, and the high
voltage components are de-energized, the oven lamp
remains on, and the digital read-out displays the time still
remaining in the cook cycle when the door was opened.
7. The monitor switch electrically monitors the operation of
the primary interlock switch and secondary interlock
relay (RY2) and is mechanically associated with the door

OPERATION

DESCRIPTION OF OPERATING SEQUENCE
so that it will function in the following sequence.
(1) When the door opens from the closed position, the
secondary interlock relay (RY2) and primary interlock
switch open their contacts. And contacts of the relay
(RY1) remains closed. Then the monitor switch contacts
close.
(2) When the door is closed from the open position, the
monitor switch contacts open first. Then the contacts of
the primary interlock switch and door sensing switch
close. And contacts of the relay (RY1) open.
If the primary interlock switch and secondary interlock relay
(RY2) fail with the contacts closed when the door is opened,
the closing of the monitor switch contacts will form a short
circuit through the monitor fuse, primary interlock switch,
relay (RY1) and secondary interlock relay (RY2), 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 (RY2) which is operated by the
control unit within a 32 second time base. Microwave power
operation is as follows:
VARI-MODE DISPLAY
100%
approx. 90% power
approx. 80% power
approx. 70% power
approx. 60% power
approx. 50% power
approx. 40% power
approx. 30% power
approx. 20% power
approx. 10% power
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.
POWER OUTPUT REDUCTION
If the oven is set for more than 30 minutes at 80, 90 or 100%
power level, after the first 30 minutes the power level will
automatically adjust itself to 70% power to avoid overcook-
ing.
SENSOR COOKING CONDITION
Using the SENSOR function, the food is cooked without
figuring time, power level or quantity. When the oven senses
enough steam from the food, it relays the information to its
microprocessor which will calculate the remaining cooking
time and power level needed for best results. When the food
6
ON TIME OFF TIME
HIGH 32 sec. 0 sec.
P-90 30 sec. 2 sec.
P-80 26 sec. 6 sec.
P-70 24 sec. 8 sec.
P-60 22 sec. 10 sec.
P-50 18 sec. 14 sec.
P-40 16 sec. 16 sec.
P-30 12 sec. 20 sec.
P-20 8 sec. 24 sec.
P-10 6 sec. 26 sec.
P-0 0 sec. 32 sec.