Commodore 1940 - Video Processing Circuit

3. VIDEO PROCESSING CIRCUIT
~: 1 Video Pramplifier
3.1.1 Contrast Control
- ___ --------tl-----a....----Vcc (8V)
r-------r----a....------- SIGNAL OUTPUT
<Fig.3 Internal Contrast Control Circuit>
CONTROL
VOLTAGE
Fig.4 is an internal equivalent contrast control circuit of TA8631 N. Current flowing in 01, 03 determined by voltage
applied to the terminal 2 of TA8631 N.
3.1.2 Blanking
Blanking pulses make the retace lines invisible by biasing the signal amplitude to black level during time the
scanning circuits produce retraces.
(a) RGB Signal
Black Level
n n II (b) Blanking Pulse
-----'- '-- --------"- '-- -----------', L Black Level
=LJ=LJ==\s (clOulpu' Signa'
<Fig.4>
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