Sharp R-950A Service Manual page 16

DAMPER OPEN-CLOSE MECHANISM
Usually, the damper is in the open position except during
convection cooking.
Damper position is set automatically by damper motor,
damper switch, motor cam and damper shaft.
These components are operated by a signal that judges if
microwave cooking or convection cooking operation is
selected by the CPU unit.
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 cavity into a
condensation compartment.
Convection Cooking:
Damper is in the closed position, so that no hot air will be
allowed to leak out the oven cavity.
Damper Operation
1. When power supply cord is plugged in:
1-1. When power supply cord is plugged in, a signal is
sensed in the control unit, and operates shut-off relay
(RY4).
1-2. Contacts of shut-off relay (RY4) close, the damper
motor is energized, opening the damper door.
1-3. When the damper is moved to the open position by
the damper cam, damper switch is closed (ON
position).
1-4. The signal of damper switch is re-sensed in the
control unit and shut-off relay (RY4) is turned off.
1-5. The rated voltage to the damper motor 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:
3-1 Damper motor is energized by touching the convection,
temperature and START pads.
3-2. When damper is in the closed position (damper
switch is OFF), its signal is sensed by the control unit,
and shut-off relay (RY4) is de-energized.
3-3. The damper is held in the closed position during the
convection cooking operation.
3-4. At the end of the convection cooking, shut-off relay
(RY4) 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 or open during
microwave, the control unit will stop oven operation
after 1 minute.
Cooking Mode
Microwave cooking
Convection cooking
Grill cooking
Simul Convection cooking
Simul Grill cooking
Operation of Damper
OPEN
CLOSE
CLOSE
CLOSE
CLOSE
DAMPER SHAFT
Figure D-2. Damper Mechanism
NOISE FILTER
The noise filter prevents the radio frequency interference
that might flow back in the power circuit.
9
R-950A
DAMPER DUCT
DAMPER
DAMPER CAM
DAMPER SWITCH
DAMPER MOTOR