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2-2-3 H. POSITION control circuit
Horizontal display position is adjusted by shifting horizontal sync. signal to be input. Horizontal
sync. signal is input to IC553 pin 1 1 . The shift time is determined by the time constant of CR to be
connected to pin 1 4. The shifted pulse is input to IC451 pin 8.
Adjustment is made according to the mode as foll ows:
VGA
800X600
MAC:II
2-2-4
H. DRIVE circuit
T he ho rizo n tal p r e - dr iv e pul se output from IC451 pin 1 5 i s input to 0501 , then it passes through
T501 to turn on a horizontal output transistor 0502.
2-2-5
H.
OUTPUT
circuit
The signal from T501 turns on and off a horizontal output transistor 0502. Co nseq u e n t l y
damper diode D501 and 0502 are turned on and off alternately so that the saw-tooth current flows
into the horizontal deflection coil.
The fly-back transformer T502 boosts up the 0502 output to approximately 23.5kV at the time of
cut off CRT anode current.
2-2-6 H. raster centering switching circuit
The raster position is controlled by superimposing DC current onto the deflection yoke current.
This DC power is generated by rectifying and smoothing T502 ( F.B.T) pulses. The inserting
position and direction of connector RH switches over the shift amount and direction of raster.
2-2-7 High voltage protector circuit
The voltage of T502 pin 5 rises as high voltage becomes higher. The high voltage protector IC451
works to stop horizontal oscillation when the voltage of IC451 pin 1 6 exceeds approximately 0.72V
(0.65 to 0.79V).
2-2-8 12V regulation circuit
The 1 2V regulation circuit regulates the power generated by rectifying the output pulses of T502
( F.B.T) to 1 2V and supplies it.
3. Vertical System
3-1 Vertical oscillation
Vertical free-run frequency is determined by an external resistor and capacitor of IC451 pins 5 and
6. Vertical oscillation occurs synchronously with sync. signal that has higher frequency than
tree-run frequency when that sync. signal is input to IC451 pin 7.
3-2 V. DRIVE, V.
OUT
The IC401 contains a vertical drive, vertical out and pump-up circuits.
Output is generated from IC401 pin 2 and is sent as the vertical deflecting current to the V. DY.
VR552
VR553
VR554
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33
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a
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