TOVIS P/N
MTG-1972XN
DATE
2002.03.11
REV NO.
0
TOVIS
Color Monitor Service Manual
PAGE
23/30
8-2.3. B+ Regulator
B+ PWM regulator output is available on pin 28 of IC301 for driving the
B+ control stage. This PWM output is adjusted through VR301.
8-3. Vertical Deflection (IC201)
IC201 (KA2142) is used for direct driving of vertical deflection yoke.
8-4. Horizontal scan voltage control stage
The step-up converter is used in this stage.
The output pulse at pin 28 of the IC301 is synchronized on horizontal
frequency. And this pulse is operated via buffer stage Q311/Q312.
This output is rectified through D315/L304.
In this way, the supply voltage to the fly-back transformer can be proportional
to the horizontal line frequency.
8-5. Horizontal deflection output stage
8-5.1. Line driver stage
As a driver device, small MOSFET Q307 (IRF630) is used.
The driver transformer T302 is equipped with a snubber circuit
(R327/C309) at the primary side to damp excessive ringing.
8-5.2. Horizontal power output stage
The horizontal power output stage is a conventional one with a diode
modulator.
As a deflection transistor, the Q308 (2SC5682) is used.
To compensate the horizontal linearity, T301 is connected in a series
with the horizontal DY. It is controlled by DC collector voltage of Q304,
which the base voltage of Q304 is integrated from output at pin 22 of
IC601.
8-5.3. S-correction capacitor switches
Q316 is off when horizontal frequency is 35KHz.
Q316, Q317 is off when horizontal frequency is 37KHz.
Q316, Q318 is off when horizontal frequency is 43KHz-52KHz.
Q317, Q318 is off when horizontal frequency is 53KHz
∼
61KHz.
Q316, Q317,Q318 is off when horizontal frequency is 62KHz
∼
70KHz.
Q316, Q318 is off when input is override condition.
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