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R-820BK
R-820BW
ROAST COOKING CONDITION
Touch the ROAST pad once. And then program desired
cooking time by touching the number pads. The ROAST
pad is preprogrammed for 325˚F with 30% microwave
power.
NOTE: The microwave power can not be changed. To
change the temperature, touch the ROAST pad
twice. When the display says "SELECT TEMP",
touch desired temperature pad.
When the START pad is pressed, the following operations
occur:
1. The numbers on the digital read-out start to count down.
2. The shut-off relays(RY1, RY5 and RY6) are energized,
turning on the oven lamp, turntable motor, cooling fan
motor and convection motor.
3. The microwave relay(RY2) is energized for 16 seconds
within a 48 second time base.
4. The heater relays(RY3 and RY4) are energized
intermittently within a 48 second time base. The power
output is set in accordance with the following table.
Selected Temp- Top Heaters Bottom Heaters
erature (˚F) Power (%) Power (%)
100 20 40
150 30 50
275 50 60
300 60 70
325 70 70
350 70 70
375 70 70
400 70 70
425 70 70
450 70 70
5. The microwave relay(RY2) and the heater relays(RY3
and RY4) are not energized simultaneously.
ON/OFF TIME RATIO
In grill cooking, convection cooking or roast cooking, the top
heaters, bottom heater or magnetron operate whithin a 48
second time base. The following table is the ON / OFF time
ratio at each power output of the top heaters, bottom heater
or magnetron.
POWER OUTPUT ON TIME OFF TIME
100% 48 sec. 0 sec.
90% 44 sec. 4 sec.
80% 40 sec. 8 sec.
70% 36 sec. 12 sec.
60% 32 sec. 16 sec.
50% 26 sec. 22 sec.
40% 22 sec. 26 sec.
30% 16 sec. 32 sec.
20% 12 sec. 36 sec.
10% 8 sec. 40 sec.
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 is accomplished by the LSI repeatedly measuring 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 voltage
measured is 700mV 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,
oven lamp and turntable motor. The LSI also stops counting
down. 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 700mV 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, oven lamp
and turntable motor. The LSI also stops counting down.
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.
THERMISTOR
SENSING
VOLTAGE
ON
OFF
ON
OFF
0 2 32 64 (sec.)
3 sec.
Sensing the voltage across temperature
measurement circuit.