R-464 (serv.man7). Complete - Sharp Home Appliance Service Manual (repair manual). Page 7

5

The thermal cut-out, located on the top of the oven cavity,
is designed to prevent damage to the oven by fire. If the
foods load is overcooked, by either error in cook time or
defect in the control unit, the thermal cut-out will open.
Under normal operation, the oven thermal cut-out remains
closed. However, when abnormally high temperatures are
reached within the oven cavity, the oven thermal cut-out
will open at 125˚C, causing the oven to shut down. The
defective thermal cut-out must be replaced with new one.

The thermal cut-out located near the magnetron is de-
signed 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 125˚C causing the oven to shut down.  The
defective thermal cut-out must be replaced with new one.

The thermostat protects the high voltage transformer
against over heating. If the temperature goes up higher
than 150˚C because the fan motor is interrupted or the
ventilation openings are blocked, the thermostat will cycle,
line voltage to the high voltage transformer will also cycle.
(If operated, check the magnetron for damage.)

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 vents surrounding
the magnetron and cools the magnetron. This air is
channeled through the oven cavity to remove steam and
vapors given off from the heating foods. It is then ex-
hausted through the exhausting air vents at the oven
cavity

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

The door is opened by pulling the door, refer to the Figure
D-1.

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.

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. interlock switch and the relay RY1 fail to
open, the fuse blows  simultaneously with closing the
contacts (COM-NC) of the monitor switch.

CAUTION: BEFORE REPLACING A BLOWN FUSE

TEST THE 1ST. INTERLOCK SWITCH,  RE-
LAY  RY1, MONITOR SWITCH AND MONI-
TOR RESISTOR FOR PROPER OPERA-
TION.

Ω

The monitor resistor prevents the fuse bursting when the
fuse blows due to the operation of the monitor switch.

The high voltage fuse blows when the high voltage rectifier
or magnetron is shorted.

1. The fuse blows when the contacts (COM-NO) of the

1st. interlock switch and the relay RY1 remain closed
with the oven door open and when the monitor switch
closes.

2. If the wire harness or electrical components are short-

circuited, this fuse blows to prevent an electric shock or
fire hazard.

Latch 
Heads

Door

Latch Hook

2nd. Interlock
Relay Control
Switch

1st. Interlock
Switch

Monitor Switch