GE 4PE21A1 Instructions Manual page 26

EBI-36.57
11.
Manual Operation
a,.
When
the Channel
is
operating under normal conditions,
compenastion for variations
in film densities should
be
made
by
adjusting
the
`Jidicon
Control Panel TARGET control,
R24,
It
is
not
recommended
that the CONTRAST control
be
used for level riding.
b.
The
signal electrode (target)
voltage controls the
sensitivity
of the
Vi_dico.i
tube. By
using
the
TARGET control for
level adjustments, advantages can
be
gained over other gain
control methods. Operating
in this
manner will assure constant signal
to noise ratio.
c.
Depress
the
Vidicon Control Panel GAIN TEST switch,
Si.
This will result in
a
test signal corresponding to
0.3
microamperes
bei.i:
applied
to the camera
preamplifier
input.
The
Channel
stability
is such that only the TARGET and BLANKING controls will
have to
be
adjusted
by the operator. The adjustment
of
these controls
will depend
on the
variations that arise
in program material.
12.
Automatic Target Control
(ATC)
An automatic target control facility
is
provided for
automatically controlling
the
output level. This control
i8 on
the
Vidicon Control Panel.
The ATC control
is set in the
following
manner:
a. Set the TARGET
AUTO/MAN
switch, S3, to
AUTO then
adjust
the TARGET control,R24,
(use
a
fairly dense film) for
the
desired output
level. The output level should
be
between
80
-.and
100 percent.
This can
he
measured
on the
monitor oscilloscope.
When thin density film
is used,
it is
compensated for
by
controlling
the
target voltage. An increase
in light will reduce the target
voltage
to
a
value under 10 volts. Capping the camera lens will
increase
the target voltage to 30 volts.
If it is
necessary,
the
camera -15V ADJ control,
R63, should
be
adjusted to produce -15 volts
as
measured
at the
camera ATC VOLTAGE, test jack, J8.
Capping
the
camera lens will produce
a
voltage reading
of 30 volts
as
measured
on the
Vidicon Control Panel TARGET VOLTAGE meter, Ml.
b.
When substituting thin density film
for,
dense film,
the
abrupt changes are compensated for in
apoximately
three TV
fields. In order tb ensure that there will
be
no white overshoot,
adjust
the
Channel Amplifier WHITE CLIP ADJ control,
R65,
counter-
clockwise
to clip the
picture portions which exceed
the
desired level.
11