R-334 (serv.man4). Complete - Sharp Home Appliance Service Manual (repair manual). Page 10

R-334 - 10

FUSE F1 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 monitored latch switch SW1

remains closed with the oven door open and when the
monitor switch SW2 closes.

3. The fuse blows when the asymmetric rectifier, H.V.

rectifier, H.V. wire harness, H.V. capacitor, magnetron
or secondary winding of power transformer is shorted.

°

The thermal cut-out protects the magnetron against
overheat. If this temperature goes up higher than 125

°

C

because the fan motor is interrupted, the ventilation openings
are blocked, the thermal cut-out TC1 will open and line
voltages to the power transformer T will be cut off and the
operation of the magnetron MG will be stopped. The defective
thermal cut-out TC1 must be replaced with new one.

°

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 oven thermal cut-out remains closed. How-
ever, 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 TC2 must be replaced with new one.

TURNTABLE MOTOR
The turntable motor drives the turntable roller assembly 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 va-
pours given off from the heating foods. It is then exhausted
through the exhausting air vents at the oven cavity.

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

DOOR OPEN MECHANISM
The door can be opened by pulling the door open.

MONITORED LATCH SWITCH SW1
STOP SWITCH SW3
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 SW2
1. When the oven door is closed, the contacts (COM - NC)

must be opened and the contacts (COM - NO) must be
closed.

2. When the oven door is opened,  the contacts (COM -

NC) must be closed and the contacts (COM - NO) must
be open.

3. If the oven door is opened and the contacts (COM - NO)

of the monitored latch switch SW1 fail to open, the fuse
F1 F8A blows simultaneously with closing the contacts
(COM - NC) of the monitor switch SW2.

CAUTION: BEFORE REPLACING A BLOWN FUSE

F1 F8A TEST THE MONITORED LATCH
SWITCH SW1, MONITOR SWITCH SW2
FOR PROPER OPERATION. (REFER TO
CHAPTER ”TEST PROCEDURE”.)

Latch Hooks

Stop Switch
SW3

Monitor Switch
SW2

Monitored Latch
Switch SW1