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Theory of Operation
- 067-1039-00
VIDBO LOGIC AND DRIVERS
0
This schematic diagram consists
of Power Supplies,
Video
Logic,
and Video Drivers.
Power Supplies
The Power Supplies
provide the following
de voltages:
+15 V, +12
V, +11.7 V, +10 V, +5 VA, +5 VB, -10 V, -12 V, and -15 V.
The +15 V and -15 V supplies
together
with a +8 V supply provided
by
the
TM500 host
mainframe
are
used
to
derive
the rest
of the
supplies.
The +12 V, +5 VA, +5 VB, and -12 V supplies
are obtained
through
the
use
of
1% regulators.
The rest
of the supplies
are obtained
by
placing
the appropriate
zener diodes across the proper de busses,
with
the exception
of the +15 V and -15 V.
Video Logic
The Video Logic circuitry
combines
a
number
of
video
signals
generated
in
other parts
of the Horizontal
Sync Generator
board, and
other video signals
from the Horizontal
Line
Generator
and
Vertical
Sync Generator
boards.
These
signals
consist
of the Vertical
Bar;
Horizontal
Blanking;
Vertical
Blanking;
Bounce (alternate
"on"
and
"off"
blanking
signal);
V Line,
and
signals
resulting
from the
positions
of the program switches
(front
panel controls)
such as V Bar
Enable
(labeled
GG),
V Line
Enable (labeled
AA), Horizontal
Video
(labeled
VV); and External
Video.
These signals
are combined with
a
series
of gates resulting
in a drive signal
at the output of U355C.
A Vertical
Sync signal
from U238A on the Vertical
Sync Generator
board
is
buffered
by U495B resulting
in TTL V SYNC available
at the
front
panel.
The output of the Video Logic circuit
(pin 8 of U355C) drives
the
Video Output Drivers.
Video Output Drivers
This circuitry
consists
of a TTL video driver
(U495A, Q396, and
Q398) and a television
video driver.
3-5
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