Operation; Description Of Operating Sequence - Sharp R-1880LS Service Manual

The following is a description of component functions during
oven operation.
OFF CONDITION
Closing the door activates the door sensing switch and secondary
interlock switch. (In this condition, the monitor switch contacts
are opened.)
When oven is plugged in, 10 volts A.C. is supplied to the control
unit. (Figure O-1).
1. The display will show "Welcome".
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 touching the NUMBER pads. W hen
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-)
RELAY CONNECTED COMPONENTS
RY1 Oven lamp
RY Power transformer/ Stirrer motor
RY4 Turntable motor
RY5 Fan motor
. 10 volts A.C. is supplied to the primary winding of the power
transformer and is converted to about 3.3 volts A.C. output
on the filament winding, and approximately 000 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, monitor switch,
door sensing switch, secondary switch and third door switch
and primary interlock relay are activated with the following
results. The circuits to the stirrer motor, the cooling fan motor,
the turntable motor, and the high voltage components are
de-energized, and the digital read-out 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 secondary and third door door switch and primary interlock
relay 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 primary
interlock relay, door sensing switch, secondary and third
door switch open their contacts, and then the monitor
switch contacts close.
() When the door is closed from the open position, the

OPERATION

DESCRIPTION OF OPERATING SEQUENCE

monitor switch contacts first open, and then the contacts
of the secondary and third door switch close.
If the primaryswitch, secondary switch and secondary interlock
relay fail 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, secondary switch ,third door switch and
primary interlock relay, causing the monitor fuse to blow.
POWER LEVEL P-0 TO P-90 COOKING
When Variable Cooking Power is programmed, the 10 volts
A.C. is supplied to the power transformer intermittently through
the contacts of relay (RY) which is operated by the control unit
within an interval second time base. Microwave power operation
is as follows:
VARI-MODE
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 (P-0)
(approx. 0% 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.
 seconds are needed for heating of the magnetron
filament.
CONVECTION COOKING CONDITION
PREHEATING CONDITION
Program desired convection temperature by touching the PRE-
HEAT pad and the temperature pad.
When the START pad is touched, the following operations oc-
cur:
1. The coil of shut-off relays (RY1, RY4, RY5 and RY7) are
energized, the oven lamp, turntable motor, cooling fan motor
and convection motor are turned on.
. The coil of relay (RY6) is energized by the control unit. The
damper is moved to the closed position, opening the damper
switch contacts. The opening of the damper switch contacts
11
ON TIME OFF TIME
3 sec.
30 sec.
6 sec.
4 sec.
 sec.
18 sec.
16 sec.
1 sec.
8 sec.
6 sec.
0 sec.
R-1880LS/LST
0 sec.
 sec.
6 sec.
8 sec.
10 sec.
14 sec.
16 sec.
0 sec.
4 sec.
6 sec.
3 sec.