Sharp Carousel R-990K, Service Manual

R990K(W)

5 – 3

3. Sensor detects moisture and humidity and calculates cooking time

and variable power.

[6] 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 SENSORCOOKING

immediately after plugging in the unit.Wait two minutes before
coo

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 the2nd. 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 dis-

play 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.

[7] MULTI COOK

MULTI COOK will automatically compute and set the oven tempera-
ture, microwave power and cooking time for baking 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, Convection
cooking mode or Preheating mode according to the special cooking
sequence.

[8] 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)

[9] 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 (thermistor) during it's 32-sec-
onds time base comparing the obtained voltage measurements. If the
most recent volt-age measured is 300mV grater than the previous volt-
age measured, the LSI judges it as a fire in the oven cavity and
switches off the relays to the power transformer, fan motor and con-
vection 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 29seconds. Two (2) sec-
onds after the thermistor is energized, the voltage across the tem-
perature 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 con-
vection 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 pro-

grammed 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 detection.

MIC R

OW

AVE

AH S E NS OR

C ONV E C T ION

MOT OR

T HE R MIS T OR

S ens ing

V oltage

ON

OF F

ON

OF F

ON

OF F

0 2 3

24

30

32 (s ec.)

64 (s ec.)

3 s ec.

S ens ing the voltage acros s temperature meas urement circuit.

6 s ec.