Sharp R-9H56, Service Manual, Page: 7 / 48

R-9H56
5
2. The coil of relay (RY4) is energized by the CPU unit. The
damper is moved to the closed position, opening the
damper switch contacts. The opening of the damper
switch contacts sends a signal to the LSI on the CPU unit
de-energizing the relay (RY4) and opening the circuit to
the damper motor.
3. The coil of heater relay (RY3) is energized by the CPU
unit and the main supply voltage is added to the convection
heater.
4. When the oven temperature reaches the selected preheat
temperature, the following operations occur:
4-1. The heater relay (RY3) is de-energized by the CPU
unit temperature circuit and thermistor, opening the
circuit to the convection heater.
4-2. The oven will continue to function for 15 minutes,
turning the convection heater on and off, as needed to
maintain the selected preheat temperature. The oven
will shut-down completely after 15 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. Program desired cooking
time and convection temperature by touching the number
pad, CONVECTION pad and Temperature pad. When the
START pad is touched, the following operations occur:
1. The numbers of the digital read-out start the 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 convection heater 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 116˚C, the circuit to (RY6) will be maintained (by
the thermistor circuit) to continue operation of the cooling
fan motor until the temperature drops below 116˚C, 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. This will now cool and allow the damper door
to open.
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
Program desired cooking time and temperature by touching
the number pads and the LOW MI or HIGH MIX pad. When
the START pad is touched, the following operations occur:
1. The numbers of the digital read-out start the count down
to zero.
2. The shut-off relay (RY1+RY5+RY6) energized, turning
on the oven lamp, turntable motor, cooling fan motor and
convection 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, adding the mains
supply voltage to the convection heater.
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 added to the convection
heater and power transformer alternately.
6-2. The convection heater operates through the heater
relay (RY3) contacts and the power transformer operates
through the cook relay (RY2) contacts.
6-3. These are operated by the CPU 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.
12 SEC. 20 SEC.
32 SEC.
LOW MIX
BAKE
HIGH MIX
ROAST
MICROWAVE POWER
= APPROX. 30%
CONVECTION
TEMPERATUE
= 300˚F
MICROWAVE POWER
= APPROX. 10%
CONVECTION
TEMPERATUE
= 350˚F (180˚C)
26 SEC. 6 SEC.
ON
ON
OFF
OFF
OFF
ON
(MICRO.)
(CONVEC.)
(MICRO.)
(CONVEC.)
Note: During alternate Microwave/Convection operation,
the convection heater is energized only if the cavity
temperature drops below the set temperature.
ABSOLUTE HUMIDITY SENSOR (AH SENSOR)
COOKING CONDITION
In case where the AH sensor is used (REHEAT SENSOR or
SENSOR INSTANT ACTION), the foods are cooked in
microwave cooking mode 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 vapour is developed. The
sensor “senses” the vapour and its resistance increases
gradually. When the resistance reaches the value set ac-
cording to the menu, supplementary cooking is started.
The time of supplementary cooking is determined by experi-