R-90GCK (serv.man5). Operation sequence and function of important components - Sharp Home Appliance Service Manual (repair manual). Page 2

5

PREHEATING CONDITION
Program desired convection temperature by touching the
CONV.(˚C) key. When the START key is touched, the
following operations occur: (Figure O-3)
1. The coil of shut-off relays (RY1, RY3 and RY5) are

energized, the oven lamp, cooling fan motor, turntable
motor and convection motor are turned on. The contacts
(COM-NO) of relay RY6 are opened.

2. The coil of relay (RY4) is energized by the control unit.

The damper is moved to the closed position, closing
the damper switch contacts. The closing of the damper
switch contacts sends a signal to the LSI on the control
unit de-energizing the relay (RY4) and opening the
circuit to the damper motor.

3.  The solid-state relays are energized by the control unit

and the main supply voltage is applied to the top and
side heating elements.

4. When the oven temperature reaches the selected

preheat temperature, the following operations occur:
4-1. The solid-state relays are de-energized by the

control unit temperature circuit and thermistor,
opening the circuit to the heating elements.

4-2. The oven will continue to function for 30 minutes,

turning the heating elements on and off, as needed
to maintain the selected preheat temperature. The
oven will shutdown completely after 30 minutes

Enter the cooking time by touching TIME keys and select
the temperature by touching CONV.(˚C) key. When the
START pad is touched, the following operations occur:

1. The numbers on the digital read-out start to count down

to zero.

2. The oven lamp, turntable motor, cooling fan motor and

convection motor are energized. The contacts (COM-
NO) of relay RY6 are opened.

3. The damper is moved to the closed position.
4.  The solid-state relays are energized (if the cavity

temperature is lower than the selected temperature)
and the main supply voltage is applied to the heating
elements to return to the selected cooking temperature.

5. Upon completion of the cooking time, the audible signal

will sound, and oven lamp, turntable motor, cooling fan
motor and convection motor are de-energized. At the
end of the convection cycle, if the cavity air temperature
is above 111˚C, the circuit to RY5 will be maintained (by
the thermistor circuit) to continue operation of the cooling

fan motor until the temperature drops below 90˚C, at
which time the relay will be de-energized, turning off the
fan motor. Relay RY3 will however, open as soon as the
convection cycle has ended, turning off the convection
fan motor.

6. At the end of the convection cook cycle, if the cavity air

temperature is below 120˚C, shut-off relay (RY4) is
energized turning on the damper motor. The damper is
returned to the open position, closing the damper
switch contacts which send a signal to the control unit,
de-energizing shut-off relay (RY4).

Enter cooking tim nd then touch the GRILL key. When the
start pad is touched, following operations occur;

1. The contacts of the relays RY1, RY3 and RY5 are

closed, and the oven lamp, turntable motor, convection
motor and fan motors are energized. The contacts
(COM-NO) of relay RY6 are closed.

2. The damper is moved to the closed position.
3. The solid-state relays are energized and the main

supply voltage is applied to the top and side heating
elements.

Enter cooking time and then touch DUAL1 key. When the
start pad is touched, following operations occur;

1. The contacts of the relays RY1, RY3 and RY5 are

closed, and the oven lamp,  turntable motor, convection
motor and fan motors are energized. The contacts
(COM-NO) of relay RY6 are closed.

2. The damper is moved to the closed position.
3. The solid-state relays are energized and the main

supply voltage is applied to the top and side heating
elements.

4. The relay RY2 is energized and the microwave energy

is generated by magnetron.

Enter cooking time and then touch DUAL2 key. When the
start pad is touched, following operations occur;

1. The contacts of the relays RY1, RY3 and RY5 are

closed, and the oven lamp,   turntable motor, convection
motor and fan motors are energized. The contacts
(COM-NO) of relay RY6 are opened.

2. The damper is moved to the closed position.
3. The solid-state relays and relay RY2 are energized,

and the main supply voltage is applied to the top and
side heating elements and the high voltage transformer
alternately.

100% (HIGH)

32 sec. ON

70% (MEDIUM 

HIGH)

Approx. 70%

100%

24 sec. ON

8 sec. OFF

14 sec. OFF

20 sec. OFF

26 sec. OFF

50% (MEDIUM)

Approx. 50%

18 sec. ON

30% (MEDIUM 

LOW)

Approx. 30%

12 sec. ON

10% (LOW)

Approx. 10%

6 sec. ON