Function Of Important Components - Sharp R-240B Service Manual

DOOR OPEN MECHANISM
The door is opened by pulling the door, refer to the Figure
D-1.
Latch Heads
1st. Latch
Door
Switch
Figure D-1. Door Open Mechanism
1ST. LATCH SWITCH, 2ND. LATCH SWITCH AND
STOP SWITCH
1. When the oven door is closed, the contacts (COM-NO)
must be closed.
2. When the oven door is opened, the contacts (COM-
NO) must be opened.
MONITOR SWITCH
1. When the oven door is closed, the contacts (COM-NC)
must be opened.
2. When the oven door is opened, the contacts (COM-
NC) must be closed.
3. If the oven door is opened and the contacts (COM-NO)
of the 1st latch switch and 2nd latch switch fail to open,
the fuse blows simultaneously with closing the con-
tacts (COM-NC) of the monitor switch.
CAUTION: BEFORE REPLACING A FUSE TEST THE
1ST LATCH SWITCH, 2ND LATCH SWITCH,
MONITOR SWITCH, MONITOR RESISTOR
AND RELAY (RY2) FOR PROPER OPERA-
TION. (REFER TO CHAPTER "TEST PRO-
CEDURE".)
MONITOR RESISTOR 0.8 20W
The monitor resistor prevents the fuse bursting when
the fuse blows due to the operation of the monitor
switch.
FUSE
1. The fuse blows when the contacts (COM-NO) of the 1st
latch switch and 2nd latch switch remain closed with
the oven door open and when the monitor switch
closes.
2. If the wire harness or electrical components are short-
circuited, the fuse M8A blows to prevent an electric
shock of fire hazard.
HIGH VOLTAGE FUSE
The high voltage fuse blows when the high voltage rectifier
or the magnetron is shorted.

FUNCTION OF IMPORTANT COMPONENTS

Latch Hook
2nd. Latch
Switch
Stop
Switch
Monitor
Switch
THERMAL CUT-OUT 125˚C (OVEN)
The thermal cut-out located on the top of the oven cavity
is designed to prevent damage to the oven if the foods in
the oven catch fire due to over heating produced by
improper setting of cook time or failure of control unit.
Under normal operation, the thermal cut-out remains
closed. However, when abnormally high temperatures are
reached within the oven cavity, the thermal cut-out will
open at 125˚C, causing the oven to shut down. The
defective thermal cut-out must be replaced with a new
one.
THERMAL CUT-OUT 95˚C (MAGNETRON )
The thermal cut-out located on the top of the oven cavity
is designed to prevent damage to the magnetron if an over
heated condition develops in the tube due to cooling fan
failure, obstructed air guide, dirty or blocked air intake, etc.
Under normal operation, the thermal cut-out remains
closed. However, when abnormally high temperatures are
reached within the magnetron, the thermal cut-out will
open at 95˚C, causing the oven to shut down. When the
magnetron has cooled to 75˚C, the thermal cut-out closes
and cook cycle will resume.
NOISE FILTER
The noise filter prevents the radio frequency interference
that might flow back in the power circuit.
TURNTABLE MOTOR
The turntable motor drives the roller stay to rotate the
turntable.
FAN MOTOR
The fan motor drives a blade which draws external cool air.
This cool air is directed through the air vanes surrounding
the magnetron and cools the magnetron. This air is chan-
nelled through the oven cavity to remove steam and
vapours given off from the heating foods. It is then ex-
hausted through the exhausting air vents at the oven
cavity.
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R-240B