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X104 acts as a nonlinear amplifier to shape the drive
signal into a rectangular pulse having a pulse dura-
tion of 12 to 14 microseconds.
The drive signal is inverted by T102 and acts to cut
off the horizontal
output transistor X105 during the
retrace
interval. The
output circuit is conventional
and uses D]03 as the damper. To prevent sweep dis-
tortion at thé point where
damper conduction
stops
and
X105
conduction
begins,
the damper diode
is
provided with a small forward bias developed
across
C110. The action of this forward bias circuit is illus-
trated in Fig. 2-4.
UNBIASED
DAMPER
BIASED DAMPER
APPROXIMATELY
EO
40Vp-p
7
.
HORIZONTAL
DEFLECTION OUTPUT
WAVEFORMS
FIG,
2-4, FORWARD BIAS ON THE DAMPER PERMITS A SMOOTH
CROSSOVER POINT BETWEEN THE DAMPER AND THE
HORIZONTAL OUTPUT STAGE.
Deflection currents feed through C111 to the horizontal
deflection winding in the deflection yoke. R115 de-
termines
the amplitude of this current and therefore
controls the width of the vidicon's raster.
2-6. VERTICAL DEFLECTION CIRCUITS
Vertical deflection signals originate. in the blocking
oscillator
X107.
This oscillator
free runs at about
56 Hz and locks up on either the 60-Hz pulses sup-
plied by the Videocorder (VTR mode) or the 60-Hz
power-frequency (VIDEO or RF modes).
Vertical sync signals from the VTR enter the camera
at pin 2 of the VTR connector. These feed through $3
(in the VTR position) to the sync amplifier X106. In
the VIDEO
or RF positions of $3, a sample of the
power-frequency
signal
developed
across
R220
is
supplied to the sync amplifier X106.
X106 inverts the sync signals and applies them to the
blocking
oscillator
X107.
This
is a conventional
blocking
oscillator in which the duration of the off
period is determined
by the discharge
of C115
into
resistors
R124,
R123,
and R112. R124
controls
bias
to determine the point at which X107 comes into con-
duction,
and.so
controls
oscillator
frequency.
The
output sawtooth is developed by the components
C116,
R127, R128 and C117. R128 is adjustable to permit
variation
of waveshape
and so acts as the vertical
linearity control. Transistors X108 and X109 form the
driver and vertical output stage respectively. Feed-
back
is achieved
by returning the cold side of the
vertical deflection winding to a variable control R131
in the emitter circuit of X108.
Since
R131 controls
the. amount
of negative
feedback,
it serves
as the
vertical size or height control.
2-7. BLANKING CIRCUITS
Vertical
and horizontal deflection signals are com-
bined
in the blanking
circuits to form pulses that
blank the vidicon during vertical
and horizontal re-
trace, and to ''clean'' the video signal's set up level
during these retrace periods.
Horizontal
pulses from two sources, the collector of
X104 and the secondary of T102, are combined at the
base of X110,
the blanking amplifier. By combining
2-4
these pulses, a blanking pulse of correct duration is
obtained. Vertical pulses developed across R125 are
fed to X110 through two paths, one consists of C122,
R145
and D107,
the other is R143,
C123,
R144
and
D108. The latter circuit integrates the waveform. By
combining
the signals from both paths,
a pulse of
longer overall duration is obtained. The diodes D107,
D108,
and D109 permit pulse mixing at the base of
X110 and isolate the pulse sources from one
another.
X110
inverts
and squares-off
the blanking
pulses.
The full output of X110 is applied to the cathode of
the vidicon to cut off the vidicon during the blanking
periods.
A
tapped-down
output,
developed
across
R148 is applied to the ''cleaner'' switch X10.
2-8. SYNC CIRCUITS
Deflection
signals are shaped and combined
in the
sync circuits to form the sync pulses that are added
to the video and blanking signals to form the com-
posite video output. A horizontal flyback pulse, de-
veloped across the secondary of T102, and a vertical
pulse developed across R125 are mixed by D105 and
D106 to form a combined
sync signal across
R138.
The
diodes
isolate the pulse sources
from one an-
other. The combined sync signal is then fed to X111
which
inverts
the pulses
to produce
positive-going
pulses. The full output of X111 is fed to the keyed
clamp
X12
to clamp blanking
pulses
to the set-up
level. Part of the output of XI11 is fed to X12. Here
the pulses are inverted once more to form the negative
sync pulses that are added to the video output of X9
through C29 and VR-4. The latter controls the ampli-
tude of the sync component
in the composite video
output.
2-9. POWER SUPPLY
The bridge rectifier D207 — D210 supplies dc power
for the camera circuits through the series
regulator
X201.
The conduction
of X201
is controlled by the
pre-regulator X202 and the error detector X203. The
latter compares a sample of the.dc output voltage with
the reference voltage developed by the Zener diode
D201. R205 is adjusted to provide an output voltage
from the regulator of + 14 volts.
Transistor X204 acts as a constant-current supply for
the focus coil. This system ensures unchanging focus
despite
the changes
in focus
coil resistance
that
accompanies warmup. Resistor R208 adjusts the bias
on X204 to determine focus current.
High voltage for the vidicon electrodes is developed
by D205. The G2 voltage (accelerating grid) is sup-
plied from R211. A lower voltage, developed across
the Zener diode D204 is applied through R212 to the
G3/G4 connection for electrostatic focus. A variable
de voltage, picked off at the arm of R215 feeds the
target voltage (ASC) system. R215 sets vidicon sensi-
tivity and is adjusted to produce
a specified ''dark
current"' with the lens cap in place.
The lower tap on the high-voltage winding of the power
transformer feeds a half wave
rectifier that is poled
to produce a negative output. The negative dc voltage
is set by the BEAM
control and applied to the con-
trol grid of the vidicon.
A voltage divider R219 and
R220 develops the 60 Hz sync signal used for line-
lock operation in the Video/RF
operating modes
of
the camera.
A tapped filament
winding supplies. 12 volts AC to
the Viewfinder's
power circuits via pins 9 and 6 of
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