Function Of Important Components - Sharp R-880B Service Manual

R-880B
judgment that there is a fire in the oven cavity and will
switch off the relays to the power transformer, fan
motor, turntable motor and the oven lamp. The LSI
also stops counting down.
3. Once the fire sensor feature has shut the unit down, the
programmed cooking cycle may be resumed by press-
ing the "START" pad or the unit may be reset by
pressing the "CLEAR" pad.
IMPORTANT:
During sensor cooking operation, the fire sensing
operation sequence will not begin until the AH sensor
has detected vapours and initiated a sensor cooking
cycle. This is because the operation of the convection
fan would interfere with the AH sensor's vapour detec-
tion.
0 2 3 24
6 sec.
CONVECTION
MOTOR ON
OFF
3 sec.
THERMISTOR
ON
OFF
ON
Sensing
Voltage
OFF
Sensing the voltage across the temperature measurement circuit.
DOOR OPEN MECHANISM
The door can be opened by pushing the open button on the
control panel. When the open button is pushed, the switch
lever is moved upward, operating the latch head. The latch
head is moved upward and released from the latch hook.
Now, the door can be opened.
Latch Heads
Door
Figure D-1. Door Open Mechanism
1ST. LATCH SWITCH AND 2ND. LATCH SWITCH
AND STOP SWITCH
1. When the oven door is closed, the contacts (COM-NO)
of each switch must be closed.
2. When the oven door is opened, the contacts (COM-
NO) of each switch must be opened.
MONITOR SWITCH
1. When the door is closed, the contacts (COM-NC) must
be opened.
30 32 (sec.) 64 (sec.)

FUNCTION OF IMPORTANT COMPONENTS

Latch Hook
2nd. Latch Switch
Monitor Switch
1st. Latch Switch
Stop Switch
Switch Lever
ON/OFF TIME RATIO
In grill cooking, convection cooking or mix cooking, the top
heaters, bottom heater or magnetron operate whithin a 48
second time base. The following table is the ON / OFF time
ratio at each power output of the top heaters, bottom
heater or magnetron.
POWER OUTPUT
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
2. When the door is opened, the contacts (COM-NC)
must be closed.
3. If the oven door is opened and he contacts (COM-NO)
of the 1st. latch switch, 2nd. latch switch and relay
(RY2) fail to open, the fuse M10A blows immediately
after closing the contacts (COM-NC) of the monitor
switch.
CAUTION: BEFORE REPLACING A BLOWN FUSE
M10A TEST THE 1ST. LATCH SWITCH, 2ND.
LATCH SWITCH, RELAY (RY2), MONITOR
SWITCH AND MONITOR RESISTOR FOR
PROPER OPERATION. (REFER TO CHAP-
TER "TEST PROCEDURE").
FUSE M10A 250V
1. If the wire harness or electrical components are short-
circuited, this fuse blows to prevent an electric shock or
fire hazard.
2. This fuse blows when the 1st. latch switch, 2nd. atch
switch and relay (RY2) remain closed with the oven
door open and when the
monitor switch closes.
3. The fuse also blows when asymmetric rectifier, H.V.
rectifier, H.V. wire harness, H.V. capacitor, magnetron or
secondary winding of high voltage transformer is shorted.
FUSE 15A
If the wire harness or electrical components are short-
circuited, this fuse blows to prevent an electric shock or fire
hazard.
8
ON TIME OFF TIME
48 sec. 0 sec.
44 sec. 4 sec.
40 sec. 8 sec.
36 sec. 12 sec.
32 sec. 16 sec.
26 sec. 22 sec.
22 sec. 26 sec.
16 sec. 32 sec.
12 sec. 36 sec.
8 sec. 40 sec.
contacts (COM-NC) of