12
R-90GCH
Figure D-3. Flow of hot air
DAMPER OPEN-CLOSE MECHANISM
Usually, the damper is in the open position except during
convection cooking, preheat, grill, dual1, dual2 or all
cooking modes which use the top / side heating elements.
Damper position is set automatically by damper motor
DM, damper switch SW5, motor cam and damper shaft.
These components are operated by a signal that judges
if microwave cooking, convection cooking operation or
other cooking operation is selected by the control unit.
Microwave Cooking:
Damper is in the open position, because a portion of cooling
air is channelled through the cavity to remove steam and
vapors given off from the heating foods. It is then exhausted
at the top of the oven cavity into a condensation compart-
ment.
Convection, Preheat, Grill, Dual1, Dual2, or all cook-
ing modes which use the top / side heating elements:
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 DM is energized, opening the damper door.
1-3. When the damper is moved to the open position by
the damper cam the damper switch SW5 is opened
(OFF position).
1-4. The signal from damper switch SW5 is re-sensed
in the control unit and shut-off relay (RY4) is turned
off.
1-5. The rated voltage to the damper motor DM is
removed 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 and (START)+1min keys.
3-2. When damper is in the closed position (damper
switch SW5 is ON), 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, if the cavity
air temperature is below 121˚C, 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.
TROUBLESHOOTING GUIDE
When troubleshooting the microwave oven, it is helpful to
follow the Sequence of Operation in performing the checks.
Many of the possible causes of trouble will require that a
specific test be performed. These tests are given a proce-
dure letter which will be found in the "Test Procedure
"section.
IMPORTANT: If the oven becomes inoperative because
of a blown fuse F2 (F10A) in the second-
ary interlock swith SW1 - monitor switch
SW2- primary interlock relay RY2 circuit,
check the monitor switch SW2, relay (RY1),
primary interlock relay (RY2) and second-
ary interlock switch SW1 before replacing
the fuse F2 (F10A).
Hot air
Hot air
Hot air
Convection
fan
Hot air
Oven cavity left side
Oven cavity
top wall
Side heating
element unit
Side heating
element unit
Top heating element unit Top heating element unit
Turntable
Convection Mode
JET Mode
