Silicon Valley Computer SHUGART 706 User Manual download pdf (Page 39)

r

VIDEO

LOOP

THROUGH

VIDEO

IN

DCA

Ó

S4

T

0

r

BYPASS

SWITCH

Sta

TERMINATION

& DC

BLOCK

GAIN

INPUT

VIDEO

AMPL

S1

7M!

SYNCH

SEPARATOR

V

SYNCH

H

SYNCH

HORIZ

LINE

DELAY

FRAME

DELAY

VIDEO

SWITCH

SPDT

SYNCH

BURST

VIDEO

& CHROMA

HORIZ

GA"ING

MULTI

VIBRATOR

VERT

GATING

MULTI-

l

VIBRATOR

LP

FILTER

HP

FILTER

LP

FILTER

SYNCH

SYNCH

1

BURST

BURST

=

PHASE

BL R

ST

AMP

LUMINANCE

HP

FILTER

CHROMA

BLRST

AMPLITUDE

&

POLARITY

LUMINANCE

LEVEI

CHRCMA

AM°/

CHROMA

AMPLITUDE

& POLARITY

h

EFFETS EFFECTS

VIDEO

INPUT

OUTPUT INVERTER IN-OUT

SOLARIZER

INPUT

SOLARIZER

OUTPUT

EFFECTS

BOAF.D

Fig. 2 -THE CIRCUITS

FOR THE

videc palette are arranged

on two s?parate

circuit boards.

A

bypass

switch allows all

`unctions to

be

instan-ly

bypassed without having

to

reset

the Individual controls.

NTSC TIGvAL 8 -10 CYCLES

^

¡

BOF

3.58MHz SIGNAL

l!, I

)4.

IIS

V

)III

+

-

BURST

BLANK'NG

SYNCH

\

INTERVAL

PULSES

V

2.4µsec

10µsec

& BLANKING

63µsec

LINE

SCAN

`INTERVAL

53psec

OD-

LIGHT

DARK

LUM NANCE

SIGNAL

/

_CHROMINANCE

;

f

(-1

U

,-a41(t,-alg_.. ,rh.....

3 58MH MODULATED

IN

AMPLITUDE

&

PHASE

WITH

COLOR INFORMATION

FIG.

3 -AN

NTSC CDLOR SIGNAL has four individual

components. all of

which

can be separately

controlled by the video palette.

Depending on the settings of the controls,

we might get

an

improved

picture, a de-

graded picture, or

an altered picture. By

this method,

we

can custom -correct indi-

vidual faults in

the

video

signal. For all

practical purposes, we

have a graphic

equalizer

for

video.

Analog effects

A few analog

effects

am incorporated in

the

video

palette. Those are

inversion,

posterization,

and

solarization.

Inversion. shown in Fig.

4,

is

simply

what

it implies: the video signal levels are

inverted about

a given

reference axis. For

example, if zero

volts

represents max-

imum

white

and I

volt

represents max-

imum black (Fig. 4 -a), passing the signal

through an inverter such that the output is

I

volt when

the input is zero

volts,

and the

output is zero volts when

the

input is I

volt, will

produce an inverted

video

signal

(Fig. 4 -b).

Note that a true inverter

would

just

change the sign. For example, let us take

the case

of

a signal

at

+0.5 volt, which

would

represent a middle gray. Ideally, if

we

invert a gray tone, it is gray. (Gray

is its

own complementary color.) However,

a

true inverter

would

give - 0.5

volts

out-

put, which would be

whiter

than

white.

Therefore,

we

must add a DC offset of

+ I

volt to the output so a that a zero

volt

input

produces a

+

I

volt

output, thereby restor-

ing

the

original gray

(Fig.

4 -c). As shown

in Fig.

4 -d,

that can be done by adding a

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