R-82FBSTM (serv.man2) - Sharp Home Appliance Service Manual (repair manual). Page 10

R-82FBSTM - 10

D2

D1

ASYMMETRIC
RECTIFIER

HIGH VOLTAGE 
RECTIFIER

A

B

C

The door can be opened by pulling the door handle. When
the handle is pulled, the latch head is pulled, the latch head
is moved upward, and released from the latch hook now
the door can be opened.

1. When the oven door is closed, the contacts (COM-NO)

of the switch must be closed. The contacts (COM-NC) must
be opened.

2. When the oven door is opened, the contacts (COM-NO) of

the switch must be opened. The contacts (COM-NC) must be
closed.

1. When the oven door is closed, the contacts (COM-NO) of the

switch must be closed.

2. When the oven door is opened, the contacts (COM-NO) of

switch must be opened.

The monitor switch is activated (the contacts opened) by the upper
latch head on the door while the door is closed. The switch is
intended to render the oven inoperative by means of blowing the
fuse F8A when the contacts of the monitored latch switch fail to open
when the door is opened.
Function
1. When the door is opened, the contacts (COM-NC) of monitor

switch  close (to the ON condition) due to their being normally
closed and contacts (COM-NO) open. At this time the con-
tacts (COM-NO) of monitored latch switch is in the OFF
condition (contacts open) due to their being normally open
contact switches.

2. As the door goes closed, the monitor switch contacts (COM-

NC) are opened and contacts (COM-NO) are closed. The
contacts (COM-NO) of monitored latch switch and stop switch
are closed.(On opening the door, each of these switches
operate inversely.)

3. If the door is opened and the monitored latch switch  con-

tacts  (COM-NO) fail to open, the fuse F8A blows immedi-
ately after closing of the monitor switch (COM-NC) contacts.

CAUTION: BEFORE REPLACING A BLOWN FUSE F8A,

TEST THE MONITORED LATCH SWITCH AND
MONITOR SWITCH FOR PROPER OPERATION.
(REFER TO CHAPTER “TEST PROCEDURE”)

If the wire harness or electrical components are short-circuited,
this fuse blows to prevent an electric shock or fire hazard.

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 the monitored latch switch remains

closed with the oven door open and when the monitor switch
contact (COM-NC) closes.

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

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

T/C transformer converts A.C. line voltage into low voltage to
drive the control unit.

This thermal cut-out protects the magnetron against overheat.
If the temperature goes up higher than 125˚C because the fan
motor is interrupted or the ventilation openings are blocked, the
thermal cut-out will open and line voltage to the high voltage
transformer will cut off and operation of the magnetron will be
stopped. The defective thermal cut-out must be replaced with a
new one.

This thermal cut-out protects against overheating or fire inside the
oven. If the temperature rises above 160˚C the thermal  cut-out
opens, the oven will switch off.The defective thermal cut-out must
be replaced with a new one.

T

he asymmetric rectifier is solid state device that prevents

current flow in both directions. It prevents the temperature rise of
the high voltage transformer by blowing the fuse F8A when the
high voltage rectifier is shorted.

The rated peak reverse voltage of D1 of the asymmetric
r

ectifier is 6 KV. The rated peak reverse voltage of D2 of the

asymmetric rectifier is 1.7 KV. D1 and D2 of the
asymmetric rectifier or high voltage rectifier are shorted when the
each peak reverse voltage goes beyond the each rated peak
reverse voltage. (The process of the blowing the fuse F8A.)
1. The high voltage rectifier is shorted by some fault when

microwave cooking or dual cooking.

2. The peak reverse voltage of D2 of the rectifier goes beyond

the rated peak reverse voltage 1.7 KV in the voltage doubler
circuit.

3. D2 of the rectifier is shorted.
4. The large electric currents flow through the high voltage

winding of the high voltage transformer.

5. The large electric currents beyond 8A flow through the

primary winding of the high voltage transformer.

6. The fuse F8A blows by the large electric currents.
7. The power supplying to the high voltage transformer is cut off.

Latch hook

Door

SW2: Stop switch

Latch
Heads

SW3: Monitor switch

SW1: Monitored

latch switch

Tab