Sharp R-950A Service Manual

R-950A
4
The following is a description of component functions
during oven operation.
Relay and Components Connection
RELAY CONNECTED COMPONENT
RY1 Oven lamp/ Turntable motor
RY2 Power transformer
RY3 Convection heater
RY4 Damper motor
RY5 Convection motor
RY6 Fan motor
RY7 Grill heater
OFF CONDITION
Closing the door activates all door interlock switches: 1st.
latch switch and 2nd. interlock relay control switch. (In this
condition, the monitor switch contacts are closed.)
When oven is plugged in a wall outlet (220V, 50Hz), rated
voltage is supplied to the control unit. (Figure O-1):
1. The display flashes “SHARP”, "MICRO-", "WAVE",
'OVEN".
To set any programmes or set the clock, you must first
touch the STOP/CLEAR pad.
“ : “ appears in the display and the time counts up
every minute.
NOTE: When the oven door is opened, the oven lamp
comes on at this time.
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 damper switch inputs a
signal to the control unit. The coil of relay RY4 is de-
energized, opening its contacts, thereby turning off the
damper motor.
MICROWAVE COOKING CONDITION
HIGH COOKING
Enter cooking time by pressing the NUMBER pads and
then select microwave cooking and power level by press-
ing 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 relays are turned on (RY1, RY2, RY6).
(Figure O-2)
2. Rated voltage is supplied to the primary winding of the
power transformer. The voltage is converted to about
3.3 volts A.C. output on the filament winding and high
voltage of approximately 2260 volts A.C. on the high
voltage winding.
3. The filament winding voltage (3.3 volts) heats the
magnetron filament and the high voltage (2260 volts) is
sent to the voltage doubling circuit.
4 The 2450 MHz microwave energy produced in the
magnetron generates a wave length of 12.24 cm. This
energy is channelled through the waveguide (transport
channel) into the oven 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, 1st. latch switch and 2nd. interlock
relay control switch are activated with the following
results. The circuits to the turntable motor, cooling fan
motor and 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 is electrically monitoring the
operation of the 1st. latch switch and 2nd. interlock
relay control 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 potion, the 1st.
latch switch and the 2nd. interlock relay control switch
open 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 1st. latch switch and 2nd. interlock relay control
switch must be closed.
If the common and normal open contacts of 1st. latch
switch and the 2nd. 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 fuse,
1st. latch switch and the 2nd. interlock relay, causing the
monitor fuse to blow.
MEDIUM HIGH, MEDIUM, MEDIUM LOW, LOW
COOKING
When variable cooking power is programmed, the rated
voltage is supplied to the power transformer intermittently
through the contacts of the relay (RY2) which is operated
by the control unit within a 32-second time base. Micro-
wave power operation is follows:
VARI MODE ON TIME OFF TIME
HIGH (100% power) 32 sec. 0 sec.
MED HIGH (approx. 70% power) 24 sec. 8 sec.
MED (approx. 50% power) 18 sec. 14sec.
MED LOW (approx. 30% power) 12 sec. 20 sec.
LOW (approx. 10% power) 6 sec. 26 sec.
NOTE: The ON/OFF time ratio does not exactly correspond
to the percentage of microwave power, because
approx. 2 seconds are needed for heating up the
magnetron filament.
CONVECTION COOKING CONDITION
PREHEATING CONDITION (Figure O-3)
Press the PREHEAT pad and then select preheating
temperature by pressing the temperature pad. When the
START pad is touched, the following operations occur:
1. The coil of shut-off relays RY1+RY5+RY6 are
energized, the oven lamp, cooling fan motor, turntable
motor and convection motor are turned on.
2. The coil of relay (RY4) is energized by the CPU unit.
The damper is moved to the closed position, opening
OPERATION SEQUENCE

Sharp R-950A Specifications

Power

ac line voltage	220 V
microwave frequency	2450 MHz
ac power required (microwave)	1.6 kW
ac power required (convection)	1.6 kW
ac power required (grill)	1.05 kW
ac power required (simul)	3.15 kW

Oven Specifications

oven capacity	41 litre
output power (microwave)	900 W
output power (convection heater)	1500 W
output power (grill heater)	1000 W

Weight and Dimensions

width	627 mm
height	378 mm
depth	492 mm
cavity width	410 mm
cavity height	245 mm
cavity depth	410 mm
weight	29 kg