Damper Open-Close Mechanism - Sharp R-969IN Service Manual

R969(W)

[21] DAMPER OPEN-CLOSE MECHANISM

Damper position is set automatically by damper motor DM, damper
switch and motor cam. These components are operated by a signal
that judges if microwave cooking or convection cooking operation is
selected by the CPU unit.
1. Microwave Cooking:
Damper is in the open position, because a portion of cooling air is
channelled through the cavity to remove steam and vapours given off
from the heating foods. It is then exhausted at the top of the oven cav-
ity into a condensation compartment.
2. Convection Cooking:
Damper is in the closed position, so that no hot air will be allowed to
leak out the oven cavity.
3. Damper Operation
1. When power supply cord is plugged in or when the control unit
resumes after energy save mode finishes:
1) When power supply cord is plugged in, a signal is sensed in the
control unit, and operates shut-off relay (RY8).
2) Contacts of shut-off relay (RY8) close, the damper motor DM is
energized, opening the damper door.
3) When the damper is moved to the open position by the damper
cam, damper switch SW4 is closed (ON position).
4) The signal of damper switch SW4 is re-sensed in the control
unit and shut-off relay (RY8) is turned off.
5) The rated voltage to the damper motor DM is stopped and the
motor turns off.
2. When oven is microwave cooking: Damper is in the open position
3. When oven is convection cooking:
1) Damper motor DM is energized right after the oven is started.
2) When damper is in the closed position (damper switch SW4 is
OFF), its signal is sensed by the control unit, and shut-off relay
(RY8) is de-energized.
3) The damper is held in the closed position during the convection
cooking operation.
4) At the end of the convection cooking, when the fan motor FM
stops, shut-off relay (RY8) is energized, and the damper is
returned to the open position.
NOTE: If the damper door is not in the proper position, closed during
convection, grill or dual, or open during microwave, the control
unit will stop oven operation after 1 minute.
4. Operation of damper is shown below.
Cooking Mode
Microwave cooking
Convection cooking
Grill; during backed up with convection
heating element
Grill; after convection heating element
backed up has stopped
Dual (Microwave and Convection)
Dual (Microwave and Grill) Open
Fire sensing condition Closed
Operation of Damper
Open
Closed
Closed
Open
Closed
Open
Closed
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