Sharp R-980J Service Manual page 8

R-980J
2. Heat potatoes. Moisture and humidity is emitted rapidly.
You can smell the aroma as it cooks. ;
AH SENSOR
3. Sensor detects moisture and humidity and calculates
cooking time and variable power.
AH SENSOR COOKING SEQUENCE
1. In case the AH sensor cooking condition is started, the
coil of shut-off relays (RY1+RY6) are energized, the
oven lamp and cooling fan motor are turned on, but the
power transformer is not turned on.
NOTE: The oven should not be operated on AH SENSOR
COOKING immediately after plugging in the unit.
Wait five minutes before cooking on AH SENSOR
COOKING CONDITION.
2. After about 16 seconds, the cook relay (RY2) is
energized. The power transformer is turned on,
microwave energy is produced and first stage is started.
The 16 seconds is the cooling time required to remove
any vapour from the oven cavity and sensor.
(Figure O-2)
NOTE: During this first stage, do not open the door or
touch STOP/CLEAR pad.
3. The oven will go to the Mix Cooking Condition at the
2nd. or 3rd. stage when Reheat pie, Casseroles or
Desserts has been chosen. (Figure O-3)
4. When the sensor detects the vapour emitted from the
food, the display switches over to the remaining cooking
time and the timer counts down to zero. At this time, the
door may be opened to stir food, turn it or season, etc.
NOTE: In case where a small quantity of food is cooked,
the oven will stop without displaying the remaining
cooking time.
5. When the timer reaches zero, an audible signal sounds.
The shut-off relay (RY1+RY6) and cook relay (RY2)
are de-energized and the power transformer, oven
lamp, etc. are turned off.
6. Opening the door or touching the STOP/CLEAR pad,
the time of day will reappear on the display and the
oven will revert to an OFF condition.
MULTI COOK
MULTI COOK will automatically compute and set the oven
temperature, microwave power and cooking time for bak-
ing and roasting. Set the desired program by touching the
MULTI COOK pad, and number pad. Enter the weight by
touching the Number pads. When the START pad is
touched, the oven works on Mix cooking mode, Convec-
tion cooking mode or Preheating mode according to the
special cooking sequence.
EASY DEFROST COOKING
The EASY DEFROST key is a special function key to
defrost meats and poultry faster and better.
EASY DEFROST key has 4 defrost stages.
EASY DEFROST automatically defrosts roast beef, etc.
When EASY DEFROST is selected and the food weight is
entered by using the number pads, the oven will cook
according to the special cooking sequence. (Figure O-2)
FIRE SENSING FEATURE (MICROWAVE MODE)
This model incorporates a sensing feature which will stop
the oven's operation if there is a fire in the oven cavity
during microwave cooking.
This accomplished by the LSI repeatedly measures the
voltage across the temperature measurement circuit (ther-
mistor) during it's 32-seconds time base comparing the
obtained voltage measurements. If the most recent volt-
age measured is 300mV grater than the previous voltage
measured, the LSI judges it as a fire in the oven cavity and
switches off the relays to the power transformer, fan motor
and convection motor. The LSI also stops counting down
and closes the damper door so that no fresh air will enter
the oven cavity. Please refer to the following section for a
more detailed description.
Operation
Please refer to the timing diagrams below.
1. The thermistor operates within a 32-seconds time base
and it is energized for three (3) seconds and off for 29
seconds. Two (2) seconds after the thermistor is
energized, the voltage across the temperature
measurement circuit is sampled by the LSI and twenty
one (21) seconds after the thermistor is cut off the LSI
turns on the cooling fan for six (6) seconds.
2. The above procedure is repeated. If the difference
between the first voltage measured (in step 1) and the
voltage measured when the procedure is repeated
(step 2) is greater than 300mV the LSI makes the
judgment that there is a fire in the oven cavity and will
switch off the relays to the power transformer, fan
motor and convection motor. The LSI also stops
counting down and closes the damper door so that no
fresh air will enter the oven cavity.
3. Once the fire sensor feature has shut the unit down, the
programmed cooking cycle may be resumed by
pressing the "START" pad or the unit may be reset by
pressing the "CLEAR" pad.
IMPORTANT:
During sensor cooking operation, the fire sensing
operation sequence will not begin until the AH sensor
has detected vapours and initiated a sensor cooking
cycle. This is because the operation of the convection
fan would interfere with the AH sensor's vapour detec-
tion.
0 2 3 24
CONVECTION
MOTOR ON
OFF
3 sec.
THERMISTOR
ON
OFF
ON
Sensing
Voltage
OFF
Sensing the voltage across temperature measurement circuit.
6
30 32 (sec.) 64 (sec.)
6 sec.