R-4G75M (serv.man2). Section 1 Text (page 1-7) - Sharp Home Appliance Service Manual (repair manual). Page 8

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6
R-4G75(W)M
R-4G75(B)M
FUNCTION OF IMPORTANT COMPONENTS
DOOR OPEN MECHANISM
The door can be opened by pushing the door open button
on the control panel. When the door open button is pushed,
the cook 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
2ND LATCH
SWITCH
STOP
SWITCH
MONITOR
SWITCH
OPEN LEVER
DOOR OPEN BUTTON
LATCH HOOK
DOOR
PRIMARY
LATCH SWITCH
Figure D-1. Door Open Mechanism
PRIMARY LATCH SWITCH AND
2ND LATCH SWITCH SW2
STOP SWITCH.
1. When the oven door is closed, the contacts (COM - NO)
must be closed.
2. When the oven door is opened, the contacts (COM - NO)
must be opened.
MONITOR SWITCH.
1. When the oven door is closed, the contacts (COM - NC)
must be opened and the contacts (COM - NO) must be
closed.
2. When the oven door is opened,  the contacts (COM - NC)
must be closed
3. If the oven door is opened and the contacts (COM - NO)
of the primary latch switch  fail to open, the fuse  M8A
blows simultaneously with closing the contacts (COM -
NC) of the monitor switch.
CAUTION: BEFORE REPLACING A BLOWN FUSE  M8A
TEST THE PRIMARY LATCH SWITCH,
MONITOR SWITCH AND MONITOR
RESISTOR  FOR PROPER OPERATION.
(REFER TO CHAPTER ”TEST PROCEDURE”.)
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.
2. The fuse also blows when primary latch switch remains
closed with the oven door open and when the contacts
of monitor switch closes.
3. The fuse blows when the asymmetric rectifier,  H.V.
rectifier,  H.V. wire harness,  H.V. capacitor, magnetron
or secondary winding of power transformer is shorted.
FUSE 13A
If the wire harness or electrical components are short-circuited,
this fuse blows to prevent an electric shock or fire hazard.
THERMAL CUT-OUT 125
°
C  (MAG)
The thermal cut-out protects the magnetron against overheat.
If this temperature goes up higher than 125
°
C because the
fan motor is interrupted, the ventilation openings are blocked,
the thermal cut-out will open and line voltages to the power
transformer  will be cut off and the operation of the magnetron
will be stopped.  The defective  thermal cut-out  must be
replaced with new one.
THERMAL CUT-OUT 160
°
C  (OVEN)
The thermal cut-out located on the top the oven cavity is
designed to prevent damage to the oven if the foods in the
oven catch fire due to over heating produced by unproper
setting of cook time or failure of control unit. Under normal
operation, the oven thermal cut-out remains closed. How-
ever, when abnormally high temperatures are reached within
the oven cavity, the oven thermal cut-out will open at 160
°
C,
causing the oven to shut down. The defective thermal cut-out
must be replaced with new one.
THERMAL CUT-OUT 150
°
C (GRILL)
The thermal cut-out located at the bottom of the oven cavity
is designed to prevent damage to the door film and the door
screen when the oven operates in Grill or Dual cooking mode
without any foods. Under normal operation, the oven thermal
cut-out remains closed. If the temperature of the thermal cut-
out goes up higher than 150
°
C, the thermal cut-out will open
and grill heating elements will be turned off. When the
temperature of the thermal cut-out goes down lower than
130
°
C, thermal cut-out will close again.
TURNTABLE MOTOR
The turntable motor drives the turntable roller assembly to
rotate the turntable.
FAN MOTOR
The fan motor drives a blade which draws external cool air.
This cool air is directed through the air vanes surrounding the
magnetron and cools the magnetron. This air is channeled
through the oven cavity to remove steam and vapors given off
from the heating foods. It is then exhausted through the
exhausting air vents at the oven cavity.
NOISE FILTER
The noise filter prevents the radio frequency interference that
might flow back in the power circuit.
MONITOR RESISTOR 0.8
/20W
The monitor resistor prevents the fuse  M8A 250V bursting
when the fuse  M8A 250V blows due to the operation of the
monitor switch.
GRILL HEATER
The grill heater element is located on the top of the oven cavity
assembly. The heater sends out heat to grill foods.
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