R-234 (serv.man2). Part 1 Text (1-28) - Sharp Home Appliance Service Manual (repair manual). Page 10

R-234 - 10

1. The fuse F1 also blows when the H.V. rectifer, H.V. wire

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

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

circuited, the fuse F1 blows to prevent an electric shock
of fire hazard.

°

°

The thermostat protects the magnetron against overheat.
If this temperature goes up higher than 150

°

C because the

fan motor is interrupted, the ventilation openings are blocked,
the thermostat  will open and line voltages to the power
transformer will cycle and the operation of the magnetron
will also  cycle.

°

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.

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 flows
through the oven cavity to remove steam and vapors given
off from the heating foods. It is then vented through the
exhaust air vents at the rear of oven cavity.

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.

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

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.

CAUTION: BEFORE REPLACING A BLOWN FUSE (F1)

TEST THE MONITORED LATCH SWITCH
(SW1) AND MONITOR SWITCH (SW2) FOR
PROPER OPERATION. (REFER TO
CHAPTER "TEST PROCEDURE".)

Latch hook

SW3: Stop switch

Door

SW2: Monitor switch

SW1:Monitored latch switch

Latch heads