R-890SLM
6 - 1
CHAPTER 6. FUNCTION OF IMPORTANT COMPONENTS
[1] DOOR OPEN MECHANISM
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.
Figure D-1. Door Open Mechanism
Latch hook
Door
Stop switch
Latch
Heads
Monitor switch
Monitored
latch switch
Tab
[2] SWITCH
1. MONITORED LATCH SWITCH
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.
2. STOP SWITCH
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.
3. MONITOR SWITCH
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
contacts (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 to a closed position, the monitor switch
contacts (COM-NC) are opened and contacts (COM-NO)
closed and then 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 contacts
(COM-NO) fail to open, the fuse F8A blows immediately 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”).
[3] FUSE
1. FUSE 20A 250V
If the wire harness or electrical components are shortcircuited,
this fuse blows to prevent an electric shock or fire hazard.
2. FUSE F8A 250V
1. If the wire harness or electrical components are shortcircuited,
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.
[4] TC TRANSFORMER
T/C transformer converts A.C. line voltage into low voltage to
drive the control unit.
[5] THERMAL CUT-OUT
1. THERMAL CUT-OUT 125°C (MG)
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.
2. THERMAL CUT-OUT 145°C (OVEN)
This thermal cut-out protects against overheating /fire inside the
oven. The cut-out contacts will open when temperatures exceed
145°C. When the cut-out cools itself down to the operating
temperature of 115°C, the contacts of the thermal cut-out will
close again.
[6] ASYMMETRIC RECTIFIER
The asymmetric rectifier is solid state device that prevents current
flow is both directions. And 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 rectifier
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.)
D2
D1
ASYMMETRIC
RECTIFIER
HIGH VOLTAGE
RECTIFIER
1. The high voltage rectifier is shorted by some fault when
microwave cooking or combi cooking.
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