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CHANNEL AMPLIFIER
EBI-36111
The gamma correction feature
is
usually used only when
the
Channel
Amplifier
is
used with television cameras employing Vidicon
tubes.
The
transfer
curve of the Image
Orthicon tube
is of
such
a
nature that gamma
correction
is
not
normally necessary.
However,
if an
Image Orthicon tube
is
used below the "knee,"
it
may
bedesirable
to
add gamma correction.
When video reversal relay
Kl is energized, the gamma
correction feature
is
disabled because normally processed negative film
does not require gamma
correction.
FEEDBACK OUTPUT
The video input signal
to
V8
is
amplified and fed
to
the grid
of
V10.
Video outputs V9 and V10
are
series connected with
V8,
V9, and
V10 forming
the
feedback output
circuit.
The output video
at C88 is
fed back
to the cathode of V8.
Trimmer
capacitors
C50, in the cathode
circuit
of
V8,
and
C53,
in the
feedback
loop,
are
adjustments for frequency response alignment.
Four 1.0 volt outputs,
J2
through
J5,
and one 0.5 volt output are
furnished.
The 0.5 volt output
at J6 is
intended for use
at
the camera
viewfinder.
SYNC ADDER
External sync
is
applied
to
the
grid
of
sync adder
V11B through
J15.
The sync peaks are clamped
at 0
volt by CR20 with the broad part
of
the pulse
going below
the cutoff point
of
V11A.
The
gain
of
V11A
is
controlled by the SYNC HGT control, R137, which
is
used
to
adjust the percentage
of
sync
to
be used.
The sync output
of
V11A
is
coupled through C90
to
J4 and J5 via
a
jumper
to
mix
the sync
signal
with the video signal for
a
composite signal
output.
BLANKING ADDER
A negative blanking input signal
is
connected
to J13 and
applied
to
the grid
of
V22A where
the
signal
is
amplified.
The tips
of
this signal
are
clipped by diode
CR22.
The resulting waveshape
is
then applied
to
the
grids
of
V22B and V12B.
The
blanking signal
is
added
to the
video signal
by V12B
at
clipper stage
V7.
V22B
adds
blanking
to
the video
signal in the
feedback output
to
introduce added
setup.
The
mixing
of
these signals
is
performed
in the cathode circuit
of V8.
SETUP control R198
is
adjusted
to
provide
the correct amount of
desired
setup.
CR23 clips the
broad part
of
the
blanking
pulse.
9
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