R-671M - Sharp Home Appliance Service Manual (repair manual). Page 9

R-671M  -  9

This thermal cut-out protects the high voltage transformer
against overheating. 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 will
open and line voltages 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.

The door can be opened by pushing the open button on the
control panel. When the button is pushed, the open lever
pushes the lower latch head on the door upward. The latch
head is linked with the lower latch head, so now, the door
can be opened.

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 primary latch
switch - monitor switch , check the primary
latch switch and  monitor switch before
replacing the fuse F1 (F8A).

LATCH HOOK

STOP SWITCH
SW2

MONITORED
LATCH SWITCH
SW1

MONITOR SWITCH
SW3

LATCH
HEADS

OPEN LEVER

DOOR OPEN BUTTON

DOOR

FIG D-1. Door Open Mechanism

The thermal cut-out protects the oven against over heating
during grill cooking, also the thermal cut-out  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 the cooking time or failure of control unit. Under
the normal operation, the oven thermal cut-out remains
closed. However, when abnormally high temperature are
reached within the oven cavity, oven thermal cut-out will
open at 150˚C causing the oven to shut down. The thermal
cut-out will cut back in at 130˚C.

The turntable motor drives the turntable roller assembly to
rotate the turntable.

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
channelled through the oven cavity to remove steam and
vapours given off from heating food. It is then exhausted
through the exhausting air vents of the oven cavity.

The noise filter assembly prevents radio frequency
interference that might flow back in the power circuit.

The grill heating element is located on the top of the oven
cavity assembly. The grill heating element sends out heat
to grill foods.

The bottom heating element is located on the floor of the
oven cavity assembly. The bottom heating element sends
out heat to grill foods.