R-249 - Sharp Home Appliance Service Manual (repair manual). Page 7

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The temperature fuse, located on the top of the oven
cavity, is designed to prevent damage to the oven by fire.
If the food load is overcooked, by either error in cook time
or defect in the control unit, the temperature fuse will open.
Under normal operation, the temperature fuse remains
closed. However, when abnormally high temperatures are
reached within the oven cavity, the temperature fuse will
open at 248˚F(120˚C), causing the oven to shut down.

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

The turntable motor drives the roller stay 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
channelled 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.

1. When the oven is switched on at microwave cooking,

at first the contacts of the surge relay is open and the
surge current flows through the surge resistor RS.

2. And then after a few msec., the contacts of the surge

relay RY1 are closed and rated voltage are supplied to
the high voltage transformer.

3. The surge resistor RS lets the current (peak current)

flow when the oven is switched on. If the surge resistor
is defective, the home fuse or monitor fuse may break
down when the oven is switched on (microwave mode).

The door is opened by pushing the open button on the
control panel, refer to the Figure D-1.
When the open button is pushed, the open button pushes
up the switch lever, and then the switch lever pushes up
the latch head. The latch heads are moved upward and
released from latch hook. Now the door will open.

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 latch switch and 2nd. interlock relay fail to
open, the fuse blows simultaneously with closing the
contacts (COM-NC) of the monitor switch.

CAUTION: BEFORE REPLACING A FUSE TEST THE

1ST LATCH SWITCH, 2ND. INTERLOCK
RELAY AND MONITOR SWITCH FOR
PROPER OPERATION. (REFER TO CHAP-
TER "TEST PROCEDURE".)

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

latch switch, 2nd. interlock relay 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 T6.3A blows to prevent an electric
shock of fire hazard.

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

Latch Heads

Latch Hook

Door

2nd. Interlock Relay
Control Switch

Monitor Switch

Switch Lever

1st. Latch Switch