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Pin 29 is for the oscillator time constant. The discharging
resistor (RD) is included in the IC. The vertical retrace
time is determined by the time constant : C352 x (RC//
RD).
The oscillation output is internally fed to the ramp gene—
rator for obtaining the sawtooth voltage.
Fig. 25. Vertical oscillator.
(7) Ramp generator.
A linear ramp wave is generated by constant voltage charging and constant current discharging
a capa—
citor (C353) connected to Pin 27. The charge—discharge timing is controlled by the vertical oscillator out—
put. The discharging current is determined by R307, VR302 and R308 connected to Pin 25. When
rotat—
ing the V—height volume (VR302) to the right, the resistance of VR302 is reduced and then V—size de—
creases.
As the vertical output amplitude is proportional to the voltage amplitude of Pin 27, the output from IC301
Pin 2 is fed back to Pin 25 through R309 for compensating the vertical linearity.
The sawtooth wave generated by the ramp generator is fed to the internal drive block.
bce
osc
Vv
V427
ge
—
1.4Vp—p
+
Discharge
——w—> Vertical Out
Fig. 26. Vertical ramp generator.
(8) Vertical drive amplifier.
The sawtooth voltage of the ramp generator is amplified in the vertical drive amplifier inside IC501,
and
then the output through Pin 24 is applied to Pin 6 of IC301 (Vertical output IC).
The vertical output section which is consisted of the vertical drive NFB (Negative Feedback) amplifier of
IC501 and an SRPP (Shunt Regulated Push—Pull) output stage of IC301 drives a vetical deflection coil so
that the current waveform of the deflection coil will be similar to the ramp waveform at Pin 27.
Pin 26 of IC501 is the AC/DC feedback terminal from the vertical output stage. The DC bias of the ver—
tial drive NFB amplifier is determined by the DC negative feedback to Pin 26 through R312, R313
and R314. -
C354 and R310 are provided for AC negative feedback. So to speak, a series resistor (R310) converts the
DY current waveform to a similar voltage waveform, and then the output voltage waveform and the output
DC component are applied to Pin 26 through a B circuit (AC/DC feedback circuit).
The B circuit determines the output current amplitude and the center voltage, so that the linearity
of ver—
tical scanning can be compensated by above AC/DC feedback.
42
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