R-90GCK (serv.man17). Complete - Sharp Home Appliance Service Manual (repair manual). Page 8

6

Automatic cooking will automatically compute the oven
temperature, microwave power and cooking time. And
the oven will cook according to the special cooking
sequence.

Following table shows the power control for manual
cooking.

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 fire sensing feature will
operate when the microwave power level is set to 80% or
more. This is accomplished by the LSI repeatedly meas-
uring the voltage across the temperature measurement
circuit (thermistor) during it's 32-seconds time base com-
paring the obtained voltage measurements. If the most
recent  voltage measured is 300 mV greater 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 fire sensing will start after 30 minutes when the

oven is started.

2. 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
five (25) seconds after the thermistor is cut off the LSI
turns on the convection fan for three (3) seconds.

3. 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 300 mV 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.

Micro ON

Side heaer

%

-
-

70
50
30
10
70
50
30
10
70
50
30
10
70
50
30
10

0
0
0
0

-
-
-
-
-
-
-
-
-
-
-
-
-

 

-

220

o

C

220

o

C

200

o

C

220 - 250

o

C

180 - 190

o

C

40 - 160

o

C

200

o

C

220 - 250

o

C

180 - 190

o

C

40 - 160

o

C

Side heaer

%

-

100

30
50
70
90
30
50
70
90
30
50
70
90
30
50
70
90
20
20
20
20

100

60
60
60
50
50
50
50
40
40
40
40
30

Top heaer

%

-

100

30
50
70
90
30
50
70
70
30
50
70
70
30
30
10
10
10
10
10
10

100

60
50
50
50
50
40
40
40
40
30
30
30

70%

-

50%
50%
30%
10%
50%
50%
30%
10%
50%
50%
30%
10%
50%
50%
30%
10%

-
-
-
-
-
-
-
-
-
-
-
-
-

Micro 

%

10-100

-

70
50
30
10
70
50
30
10
70
50
30
10
70
50
30
10
70
50
30
10

-
-
-
-
-
-
-
-
-
-
-
-
-

Micro. OFF

Oven

temperature

Powr down

time

Power after powr down time

Manual

MENU

MICROWAVE
GRILL

REHAET

CONV.
(Normal)

DUAL1

DUAL2

Air

Balancel

Jet

Jet

Conv.

Conv.

Conv.

Conv.

Conv.

Conv.

Conv.

Conv. or Jet

-

-

-

-

-

50%

-

-

-

-

-

40 - 250

o

C

250

o

C

230

o

C

200 - 220

o

C

40 -190

o

C

250

o

C

230

o

C

200 - 220

o

C

40 - 190

o

C

250

o

C

230

o

C

200 - 220

o

C

40 - 190

o

C

 

40 min.
60 min.

All

30 min.

All

30 min.

All

45 min.

All

45 min.

None

30 min.
30 min.
20 min.
20 min.
30 min.
30 min.
20 min.
20 min.
60 min.
60 min.
30 min.
20 min.

-
-
-
-
-
-
-
-
-
-
-
-
-

50%

30%

30%

30%

-

-

30%
30%
30%
20%
30%
30%
30%
20%
30%
30%
30%
20%

-

-

-

20%

20%

20%

-

-

30%
30%
30%
20%
30%
30%
30%
20%
30%
30%
30%
20%

Top heaer Side heaer

Side heaer

Micro. 

Micro. ON

Micro. OFF

Cool oven 
(Oven Temperature 
less  than 59˚C)

After preheating 
(Oven Temperature
more than 100˚C)

Warm oven 
(Oven Temperature  
60˚C - 99˚C)