Sharp R-5L16 Service Manual page 8

R-5L16
THERMAL CUT-OUT 125
The thermal cut-out protects the magnetron against over-
heat. If this temperature goes up higher than 125°C because
the fan motor is interrupted, the ventilation openings are
blocked, the thermal cut-out TC1 will open and line voltages
to the high voltage transformer T will be cut off and the
operation of the magnetron MG will be stopped. The defective
thermal cut-out TC1 must be replaced with new one.
THERMAL CUT-OUT 125
The thermal cut-out located on the top of 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 improper
setting of cook time or failure of control unit. Under normal
operation, the oven thermal cut-out remains closed. How-
ever, when ab-normally high temperatures are reached within
the oven cavity, the oven thermal cut-out will open at 125°C,
causing the oven to shut down. The defective thermal cut-out
TC2 must be replaced with new 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 surrounding the
magnetron and cools the magnetron. This air is channelled
through the oven cavity to remove steam and vapours 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.
SURGE RELAY RY AND SURGE RESISTOR R2
Ω
10 /20W
1. When the oven is switched on the surge current (peak
current) flows through the surge resistor R2, for approx.
6msec. The surge resistor R2 puts down the surge current
(peak current).
°
C TC1 (MG)
°
C TC2 (OVEN)
2. After approx, 6msec. the contacts of the surge relay RY2
close and the line voltage is supplied to the high voltage
transformer T.
3. If the surge resistor R2 is defective, the home fuse or fuse
F2 may break down when the oven is switched on.
4. If the contacts of the surge relay RY2 remains opened after
6msec. since the oven is switched on the temperature of
the surge resistor R2 of may rise high and may damage
the electric or mechanical parts around the surge resistor
R2.
ASYMMETRIC RECTIFIER
The asymmetric rectifier is a solid state device that prevents
current flow in both directions. And it prevents the tempera-
ture rise of the high voltage transformer by blowing the
special fuse F2 when the high voltage rectifier is shorted.
A
D2 D1
ASYMMETRIC
RECTIFIER
The rated peak reverse voltage of D1 of the asymmetric
rectifier is 6 KV. The rated peak reverse voltage of D2 of the
asymmetric rectifier is 1.7 KV. D1 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 special fuse F2)
1. The high voltage rectifier is shorted by any causes when
microwave cooking.
2. The peak reverse voltage of D2 of the rectifier goes
beyond the rated peak reverse voltage 1.7 KV in the
voltage doubler circuit.
3. D2 of the rectifier is shorted.
4. The large electric currents flow through the high voltage
winding of the high voltage transformer.
5. The large electric currents beyond 10A flow through the
primary winding of the high voltage transformer.
6. The special fuse F2 blows by the large electric currents.
7. The power supply to the high voltage transformer is cut off.
6
B
HIGH VOLTAGE RECTIFIER
C