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activating both interlock switches. The primary interlock system
consists of the door sensing switch and primary interlock relay
located on the control circuit board.
LATCH
HEADS
DOOR OPEN
DOOR OPEN
BUTTON
BUTTON
Figure D-1. Door sensing switch, monitor switch and
secondary interlock switches
MONITOR SWITCH
The monitor switch is mounted on the middle position of latch
hook. It is activated (the contacts opened) by the lower latch head
while the door is closed. The switch is intended to render the oven
inoperative by means of blowing the monitor fuse when the
contacts of the primary interlock relay and secondary interlock
switch fail to open when the door is opened.
Functions:
1. When the door is opened, the monitor switch contact close
(to the ON condition) due to their being normally closed. At
this time the door sensing and secondary interlock switches
are in the OFF condition (contacts open) due to their being
normally open contact switches.
2. As the door goes to a closed position, the monitor switch
contacts are first opened and then the door sensing switch
and the secondary interlock switch contacts close. (On opening
the door, each of these switches operate inversely.)
3. If the door is opened, and the primary interlock relay and
secondary interlock switch contacts fail to open, the monitor
fuse blows simultaneously with closing of the monitor
switch contacts.
CAUTION: BEFORE REPLACING A BLOWN MONITOR
FUSE TEST THE DOOR SENSING SWITCH,
PRIMARY INTERLOCK RELAY, SECONDARY
INTERLOCK SWITCH AND MONITOR SWITCH
FOR PROPER OPERATION. (REFER TO CHAP-
TER "TEST PROCEDURE").
NOTE: MONITOR FUSE AND MONITOR SWITCH ARE
REPLACED AS AN ASSEMBLY.
THERMISTOR
The thermistor is a negative temperature coefficient type. The
temperature in the oven cavity is detected through the resist-
ance of the thermistor, and then the control unit causes the
heater relay to operate, thus the current to the heating element
is turned ON/OFF.
MAGNETRON TEMPERATURE FUSE.
The temperature fuse located on the waveguide is designed to
prevent damage to the magnetron if an over heated condition
develops in the magnetron due to cooling fan failure, ob-
structed air guide, dirty or blocked air intake, etc.
LATCH HOOK
DOOR SENSING
SWITCH
MONITOR SWITCH
SECONDARY
INTERLOCK SWITCH
SWITCH LEVER
OPEN LEVER
11
Under normal operation, the temperature fuse remains closed.
However, when abnormally high temperatures are reached
within the magnetron, the temperature fuse will open at
302˚F(150˚C) causing the oven to shut down.
CONV. THERMAL CUT-OUT
The thermal cut-out located on the left side of the thermal
protection plate (left) is designed to prevent damage to the
heater unit if an over heated condition develops in the heating
unit due to convection fan failure, thermistor failure, obstructed
air ducts, dirty or blocked air intake, etc. Under normal opera-
tion, the thermal cut-out remains closed. However, when abnor-
mally high temperatures are reached within the heater unit, the
thermal cut-out will open at 302˚F(150˚C) causing the oven to
shut down. When the thermal cut-out has cooled, the thermal
cut-out closes at 266˚F(130˚C).
HEATING ELEMENT
The heating element is located at the left side of the oven cavity.
It is intended to heat air driven by the convection fan. The
heated air is kept in the oven and force-circulated and reheated
by the heating element.
NOISE FILER
The noise filter prevents the radio frequency interference that
might flow back in the power circuit. .
CONVECTION COOKING SYSTEM
This oven is designed with a hot air heating system where food
is not directly heated by the heating element, but is heated
by forced circulation of the hot air produced by the heating
element. The air heated by the heating element is circulated
through the convection passage provided on the outer
casing of the oven cavity by means of the convection fan
which is driven by the convection motor. It then enters the
inside of the oven through the vent holes provided on the left
side of the oven. Next, the hot air heats the food on the
turntable and leaves the oven cavity through the vent in the
center of the oven cavity left side wall. Without leaving the
oven, this hot air is reheated by the heating element, passes
through the convection passage and enters the inside of the
oven cavity again, in a continuing cycle. In this way, the hot
air circulates inside the oven cavity to raise its temperature
and, at the same time, comes into contact with the food
being cooked. When the temperature inside the oven cavity
reaches the selected temperature, the heating element is
de-energized. When the temperature inside the oven cavity
drops below the selected temperature, the heating element
is energized again. In this way, the inside of the oven cavity
is maintained at approximately the selected temperature.
When the convection time reaches 0, the heating element
is de-energized and the convection fan stops operating and
the oven shuts off.
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 se-
lected by the control unit.
Microwave Cooking:
Damper is in the open position, because a portion of cooling air
R-930AK-F
R-930AW-F
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