Function Of Important Components - Sharp R-937 Service Manual

DOOR OPEN MECHANISM
The door can be opened by puiiing the door handle.
When the door handle is pulled, the latch head is moved
upward, and released from the latch hook now the door
can be opened.
Door
Latch
Heads
SW1: Monitored
latch switch
Figure D-1. Door Open Mechanism
MONITORED LATCH SWITCH SW1
1. When the oven door is closed, the contacts (COM-NO)
of the switch must be closed. And the contacts (COM-
NC) must be opened.
2. When the oven door is opened, the contacts (COM-
NO) of the switch must be opened. And the contacts
(COM-NC) must be closed.
STOP SWITCH SW2
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.
MONITOR SWITCH SW3
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 F2 F8A when the contacts of
the monitored latch switch SW1 fail to open when the door
is opened.
Function
1. When the door is opened, the contacts (COM-NC) of
monitor switch SW3 close (to the ON condition) due to
their being normally closed and contacts (COM-NO)
open. At this time the contacts (COM-NO) of monitored
latch switch SW1 is in the OFF condition (contacts
open) due to their being normally open contact switches.
2. As the door goes to a closed position, the monitor
switch SW3 contacts (COM-NC) are opened and con-
tacts (COM-NO) closed and then contacts (COM-NO)
of monitored latch switch SW1 and stop switch SW2
are closed.(On opening the door, each of these switches
operate inversely.)
3. If the door is opened and the monitored latch switch
SW1 contacts (COM-NO) fail to open, the fuse F2
(F8A) blows immediately after closing of the monitor
switch SW3 (COM-NC) contacts.

FUNCTION OF IMPORTANT COMPONENTS

Latch hook
Tab
SW2: Stop switch
SW3: Monitor switch
CAUTION: BEFORE REPLACING A BLOWN FUSE F2
F8A, TEST THE MONITORED LATCH
SWITCH SW1 AND
SW3 FOR PROPER OPERATION. (REFER
TO CHAPTER "TEST PROCEDURE").
FUSE F1 20A 250V
If the wire harness or electrical components are short-
circuited, this fuse F1 20A blows to prevent an electric
shock of fire hazard.
FUSE F2 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 the monitored latch switch
SW1 remains closed with the oven door open and
when the monitor switch SW3 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 trans-
former is shorted.
TC TRANSFORMER
T/C transformer converts A.C. line voltage into low voltage
to drive the control unit.
THERMAL CUT-OUT TC1 125˚C (MG)
This thermal cut-out protects the magnetron against over-
heat. If the temperature goes up higher than 125˚C be-
cause the fan motor is interrupted or the ventilation open-
ings are blocked, the thermal cut-out TC1 will open and
switch off all the electrical parts. The defective thermal
cut-out must be replaced with a new one.
THERMAL CUT-OUT TC2 170˚C (GRILL)
This thermal cut-out protects the oven against the over-
heat during grill cooking, convection cooking or dual
cooking. If the temperature rises above 170˚C because
the fan motor is interrupted, the air inlet duct is blocked or
the ventilation openings are obstructed, the thermal cut-
out TC2 opens and switches off all the electrical parts.
When the cools itself down to the operating temperature of
155˚C, the contacts of the thermal cut-out will close again.
THERMAL CUT-OUT TC3 170˚C (CONV.)
This thermal cut-out protects the convection motor against
the overheat. If the temperature of the thermal cut-out TC3
rises above 170˚C because the convection fan is inter-
rupted, the ventilation openings are obstructed or the
other abnormal matter occurs, the thermal cut-out opens
and switches off the convection heating element and the
other electrical parts. When the cools itself down to the
operating temperature of 155˚C, the contacts of the ther-
mal cut-out will close again.
10
MONITOR SWITCH