Sharp R-930AK-F Service Manual page 9

4. When the oven temperature reaches the selected preheat
temperature, the following operations occur:
4-1 The heater relay is de-energized by the control unit
temperature circuit and thermistor, opening the circuit
to the heating element.
4-2. The oven will continue to function for 30 minutes,
turning the heater on and off, as needed to maintain the
selected preheat temperature. The oven will shut-
down completely after 30 minutes
CONVECTION COOKING CONDITION
When the preheat temperature is reached, a beep signal will
sound indicating that the holding temperature has been reached
in the oven cavity. Open the door and place the food to be
cooked in the oven. Touch the CONVEC pad first and then
touch the Temperature pad. And program desired cooking time
by touching the Number pads. 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.
3. Heater relay (RY3) is energized (if the cavity temperature
is lower than the selected temperature) and the main supply
voltage is applied to the heating element to return to the
selected cooking temperature.
4. 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 275˚F,
the circuit to RY6 will be maintained (by the thermistor circuit)
to continue operation of the cooling fan motor until the
temperature drops below 245˚F, at which time the relay will be
de-energized, turning off the fan motor. Relay RY5 will
however, open as soon as the convection cycle has ended,
turning off the convection fan motor.
5. At the end of the convection cook cycle, 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).
AUTOMATIC MIX COOKING CONDITION
Touch the HIGH MIX/ROAST or the LOW MIX/BAKE pad first.
And then program desired cooking time by touching the Number
pads. The LOW MIX/BAKE pad is preprogrammed for 350˚F
with 10% microwave power, while the HIGH MIX/ROAST pad
is preprogrammed for 300˚F with 30% microwave power.
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 shut-off relays (RY1,RY2,RY3,RY5 and RY6) are
energized, turning on the oven lamp, turntable motor,
cooling fan motor and convection fan motor.
3. The shut-off relay (RY4) is energized.
The damper door is closed from the open position.
4. The heater relay (RY3) is energized, applying the main
supply voltage to the heating element.
5. Now, the oven is in the convection cooking condition.
6. When the oven temperature reaches the selected
temperature, the following operations occur:
6-1. The power supply voltage is alternated to the heating
element and power transformer.
6-2. The heating element operates through the heater relay
(RY3) contacts and the power transformer operates
through the primary interlock relay (RY2) contacts.
6-3. These are operated by the control unit to supply
alternately within a 32 second time base, convection
heat and microwave energy.
The relationship between the convection and microwave power
operations are as follows.
Note: The ON and 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 SEC.
ON
(MICRO.)
OFF
(CONVEC.)
12 SEC.
ON
(MICRO.)
(CONVEC.)
OFF
Note: During alternate Microwave/Convection operation,
the convection heater is energized only if the cavity
temperature drops below the set temperature.
SENSOR COOKING CONDITION
Using the SENSOR COOK function, the foods are 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 is
cooked, water vapor is developed. The sensor "senses" the
vapor and its resistance increases gradually. When the resist-
ance reaches the value set according to the menu, supplemen-
tary cooking is started.
The time of supplementary cooking is determined by experi-
ment with each food category and inputted into the LSI.
An example of how sensor works:
1. Potatoes at room temperature.
Vapor is emitted very slowly.
2. Heat potatoes. Moisture and
humidity is emitted rapidly. You
can smell the aroma as it cooks.
3. Sensor detects moisture and
humidity and calculates cooking
time and variable power.
7
26 SEC.
MICROWAVE POWER
= APPROX. 10%
CONVECTION
TEMPERATUE
= 350˚F (180˚C)
LOW MIX
BAKE
20 SEC.
MICROWAVE POWER
OFF
= APPROX. 30%
ON
CONVECTION
TEMPERATUE
32 SEC.
HIGH MIX
ROAST
AH SENSOR
R-930AK-F
R-930AW-F
= 300˚F