Function Of Important Components - Sharp R-980J Service Manual

DOOR OPEN MECHANISM
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 lever pushes up
the switch lever, and then the switch lever pushes up the
the latch head. The latch heads are moved upward and
released from latch hook. Now the door will open.
LATCH
HEADS
DOOR OPEN
BUTTON
Figure D-1. Door Open Mechanism
UPPER LATCH SWITCH, LOWER LATCH SWITCH
AND STOP SWITCH
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
The monitor switch is mounted on the latch hook. It is
activated (the contacts opened) by the lower latch head
when the door is closed. The switch is intended to render
the oven inoperative by means of blowning the fuse when
the contacts of the common and normal open contacts of
upper latch switch and lower latch switch
fail to open when the door is opened.
Functions:
1. When the door is opened, the monitor switch contacts
close (to the ON condition) due to their being normally
closed. At this time the common and normal open
contacts of upper latch switch and lower latch switch
are in the OFF condition (contacts open) due to their
being normally open contacts switch.
2. As the door goes to a closed position, the monitor
switch contacts are first opened and then the common
and normal open contacts of upper latch switch close.
(On opening the door, each of these switches operate
inversely.)
3 If the door is opened during cooking, and the common
and normal open contacts of upper latch switch and
lower latch switch fail to open, the fuse blows
simultaneously with closing of the monitor switch
contacts.
CAUTION: BEFORE REPLACING A BLOWN FUSE
TEST THE UPPER LATCH SWITCH, LOWER
LATCH SWITCH AND MONITOR SWITCH
FOR PROPER OPERATION. (REFER TO
CHAPTER "TEST PROCEDURE").

FUNCTION OF IMPORTANT COMPONENTS

LATCH HOOK
UPPER LATCH SWITCH
STOP SWITCH
MONITOR SWITCH
LOWER LATCH SWITCH
SWITCH LEVER
OPEN LEVER
THERMAL CUT-OUT 150˚C (CONV.)
The oven thermal cut-out located on the left side of the
thermal protection plate is designed to prevent damage to
the convection heater unit if an overheated condition
develops in the tube due to cooling fan failure, obstructed
air ducts, dirty or blocked air intake, etc. Under normal
operation, the oven thermal cut-out remains closed. How-
ever, when abnormally high temperatures are reached
within the heater unit, the oven thermal cut-out will open,
causing the oven to shut down. When the oven has cooled
temperature, the oven thermal cut-out closes.
THERMAL CUT-OUT 95˚C (FAN MOTOR)
The thermal cut-out protect the fan motor against over-
heating. If its temperature goes up higher than 95˚C
because the fan motor is locked or the ventilation operat-
ing are blocked, the contacts of the thermal cut-out will
open and switch off the oven. When the thermal cut-out
cools itself down to 75˚C, the contacts of the thermal cut-
out will close again.
TEMPERATURE FUSE 150˚C (MG)
This fuse protects the magnetron against overheating. If
the temperature goes up higher than 150˚C because the
fan motor is interrupted, the air inlet duct is blocked or the
ventilation openings are obstructed, the fuse blows and
cuts off the power supplying to the power transformer. The
defective fuse must be replaced with new rated one.
FUSE M8A 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 upper latch switch and lower
latch switch remain closed with the oven door open and
when the monitor switch closes.
3. The fuse M8A also blows when asymmetric rectifier,
H.V. rectifier, H.V. wire harness, H.V. capacitor,
magnetron or secondary winding of power transformer
is shorted.
ASYMMETRIC RECTIFIER
The asymmetric rectifier is a solid state device that pre-
vents current flow ins both directions. And it prevents the
temperature rise of the power transformer by blowing the
fuse M8A when the high voltage rectifier is shorted.
D2
ASYMMETRIC
RECTIFIER
The rated peak reverse voltage of D1 of the asymmetric
rectifier is 6 KV The rated peak reverse voltage of D2 of the
asymmetric rectifier is 1.7 KV. D1 and D2 of the asymmet-
ric rectifier or high voltage rectifier are shorted when the
each peak reverse voltage goes beyond the each rated
peak reverse voltage. (The process of blowing the fuse
M8A.) .
1. The high voltage rectifier is shorted by any causes
when microwave cooking.
2. The peak reverse voltage of D2 of the rectifier goes
7
R-980J
D1
HIGH VOLTAGE
RECTIFIER