Sharp R-870B, Service Manual

Page: 10 / 48

8
R-870B
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.
Figure D-1. Door Open Mechanism
FUNCTION OF IMPORTANT COMPONENTS
1ST. LATCH SWITCH AND 2ND. INTERLOCK
RELAY CONTROL 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.
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 and 2nd. interlock 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.
INTERLOCK RELAY (RY2), MONITOR
SWITCH AND MONITOR RESISTOR FOR
PROPER OPERATION. (REFER TO CHAP-
TER “TEST PROCEDURE”).
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.
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 ON TIME OFF TIME
100% 48 sec. 0 sec.
90% 44 sec. 4 sec.
80% 40 sec. 8 sec.
70% 36 sec. 12 sec.
60% 32 sec. 16 sec.
50% 26 sec. 22 sec.
40% 22 sec. 26 sec.
30% 16 sec. 32 sec.
20% 12 sec. 36 sec.
10% 8 sec. 40 sec.
Latch Hook
Latch Heads
Door
1st. Latch Switch
2nd. Interlock
Relay Control
Switch
Monitor Switch
Switch Lever
CONVECTION
MOTOR
THERMISTOR
Sensing
Voltage
ON
OFF
ON
OFF
ON
OFF
0 2 3 24 30 32 (sec.) 64 (sec.)
3 sec.
Sensing the voltage across temperature measurement circuit.
6 sec.