Sharp R-677W Service Manual page 12

FUNCTION OF IMPORTANT COMPONENTS
SPECIAL FUSE F1 20A
If the wire harness or electrical components are short-
circuited, this fuse F1 blows to prevent an electric shock of
fire hazard.
FUSE F2 F8A 250V
1. If the wire harness or electrical components are short-
circuited, this fuse blows to prevent an electric shock or
fire hazard.
2. The fuse also blows when the primary (monitored)
latch switch remains closed with the oven door open
and when the monitor switch contact (COM-NC) closes.
THERMAL CUT-OUT TC1 145˚C (HVT)
This thermal cut-out protects the high voltage transformer
against overheating. The cut-out is incorporated into the
HVT primary windings. If the temperature goes up higher
than 145˚C because the fan motor is interrupted or the
ventilation openings are blocked, the thermal cut-out TC1
will open and line voltage to the high voltage transformer
will be cut off and the operation of the magnetron will be
stopped. The thermal cut-out will cut back in at 115˚C.
THERMAL CUT-OUT TC2 150˚C (OVEN)
This thermal cut-out protects the oven against overheat-
ing during grill cooking. The thermal cut-out is also de-
signed to prevent damage to the oven if the foods in the
oven catch fire due to over heating produced by improper
setting of the cooking time or failure of the control unit.
Under the normal operation, the oven thermal cut-out TC2
remains closed. However, when abnormally high tem-
perature are reached within the oven cavity, oven thermal
cut-out TC2 will open at 150˚C causing the oven to shut
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 procedure
letter which will be found in the "Test Procedure" section.
IMPORTANT: If the oven becomes inoperative because of a blown fuse (F8A) in the monitored latch switch - monitor
switch circuit, check the monitored latch switch and monitor switch before replacing the fuse (F8A).
down. The thermal cut-out will cut back in at 130˚C.
TURNTABLE MOTOR TTM
The turntable motor drives the turntable roller assembly
to rotate the turntable.
FAN MOTOR FM
The fan motor drives a blade which draws external cool
air. This cool air is directed through the air vanes sur-
rounding the magnetron and cools the magnetron. This
air is channelled through the oven cavity to remove steam
and vapours given off from heating food. It is then ex-
hausted through the exhausting air vents of the oven
cavity.
NOISE FILTER
The noise filter assembly prevents radio frequency inter-
ference that might flow back in the power circuit.
GRILL HEATING ELEMENT (TOP GRILL) GH1
The grill heating element GH1 is located on the top of the
oven cavity assembly. The grill heating element GH1
sends out heat to grill foods.
BOTTOM HEATING ELEMENT GH2
The bottom heating element GH2 is located on the floor
of the oven cavity assembly. The bottom heating element
GH2 sends out heat to grill foods.
TROUBLESHOOTING GUIDE
R-677 - 12
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CONT