Sharp R-9H58, Service Manual

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R-9H58
7
UPPER AND LOWER LATCH SWITCHES
Those latch switches are mounted in the latch hooks as
shown in figure. They are activated by the latch heads on
the door.
When the door is opened, the switches interrupt the circuit
to all components except CPU unit and relay unit and oven
lamp. A cook cycle cannot take place until the door is firmly
closed thereby activating both interlock switches.
LATCH HOOK
STOP SWITCH
MONITOR SWITCH
SWITCH LEVER
OPEN LEVER
LATCH
HEADS
DOOR OPEN
BUTTON
UPPER LATCH SWITCH
LOWER LATCH SWITCH
Figure D-1. Switches
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
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.
CONVECTION
MOTOR
THERMISTOR
Sensing
Voltage
ON
OFF
ON
OFF
ON
OFF
0 2 24 30 64 (sec.)
3 sec.
Sensing the voltage across the temperature measurement circuit.
6 sec.
3 32 (sec.)
FUNCTION OF IMPORTANT COMPONENTS
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”).
STOP SWITCH
The stop switch is activated by the latch head.
When the door is opened while the oven is in cook cycle,
the stop switch contacts open to de-energize the relay
(RY-1,RY-2,RY-3,RY-5,RY-6). Then the cook cycle is
stopped.
THERMAL CUT-OUT 150˚C (OVEN)
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.