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the Zener diode(ZD401) turning it ON. With 0401
turned ON, the X-ray protector of 1C401 operates to
stop the horizontal oscillation,shutting down the
resultant high voltage.
POWER SUPPLY
The AC voltage is full-wave rectified by the rectified-
smoother circuit and then changed to DC voltage
by smoothing capacitor C610. When the power is
turn on, a small current flows into the base of output
transistor (included in 1C601) via the start-up resistor
(R603). As a result, the collector current flows
through the primary windings (pin 1 and pin 3 of
the power transformer T601) and then it produces
an electromagnetic force.Therefore some voltage is
induced between pin 6 and pin 7 (driving winding)
of the power tranormer. The induced voltage is
positively feedback to the base of the output tran-
sistor (included in 1C601) to increase the base current
of this transistor. As a result of this base current,
the collector current of that transistor is increased.
The above operation occurs instaneously to impress
suffiecient base current. The small signal transis-
tor(0601) protects 1C601 from the surge current and
0602 is trigger transistor. The FBT B
+
is selected
by the MODE detecting circuit. In CGA MODE, the
FBT B
+
voltage comes from pin 10 of T60 1 but in
EGA MODE the FBT B
+
comes from pin 11 of T601
by auto mode sensing circuit. Here the mode sensing
circuit let 0604 and 0603 operate.
FROM PIN@
OF T403
(AFC PULSE)
0406
R423
ZD401
0401
AC INPUT
LINE FILTER
(L60
1.
L602)
IC401
f
R422
R438
FIG.6 HIGH VOLTAGE SHUT DOWN SYSTEM CIRCUIT
RECTIFIER IC
(1C60 1)
POWER TRANS
(T60
11
T601
14
DC 85V
13
DC 24V
l-----DC 6.3V
l-----DC 12V
\----DC 54V (MODE
1)
9 l----DC 65V (MODE 2)
FIG. 7 POWER SUPPLY BLOCK DIAGRAM
-8-
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