Sharp R-4A52 Service Manual page 7

R-4A52
R-4E52
FUSE _E M8A 250A
1. If the wire harness or electrical components are
short-circuited, this fuse blows to prevent an elec-
tric shock or fire hazard.
2. The fuse blows when the asymmetric rectifier, H.V.
rectifier, H.V. wire harness, H.V. capacitor,
magnetron or secondary winding of power trans-
former is shorted.
3. The fuse also blows when upper and lower latch
switches SW1 + SW2 remains closed with the oven
door open and when the monitor switch SW3
closes.
TEMPERATURE FUSE E 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 puts the oven out of operation. The defec-
tive fuse must be replaced with new rated one.
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 sur-
rounding 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
ASYMMETRIC RECTIFIER
The asymmetric rectifier is a solid state device that
prevents current flow in both directions. And it pre-
vents the temperature rise of the power transformer by
blowing the fuse E M8A when the high voltage rectifier
is shorted.
*qlG" VOLTAGE RECTIF,ER
The rated peak reverse voltage of Dl of the asymmetric
rectifier is 6 KV The rated peak reverse voltage of D2
of the asymmetric rectifier is 1.7 KV. Dl 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 blowing the fuse E M8A.)
1.
2.
3.
4.
5.
6.
7.
The high voltage rectifier is shorted by any causes
when microwave cooking.
The peak reverse voltage of D2 of the rectifier goes
beyond the rated peak reverse voltage 1.7 KV in the
voltage doubler circuit.
D2 of the rectifier is shorted.
The large electric currents flow through the high
voltage winding of the power transformer.
The large electric currents beyond 8A flow through
the primary winding of the power transformer.
The fuse E M8A blows by the large electric currents.
The power supply to the power transformer is cut
off.
NOISE FILTER
(For New Zealand Model)
The noise filter prevents the radio frequency interfer-
ence that might flow back in the power circuit.