GE 4PE350A3 Instructions Manual page 33

COLOR CAMERA
EBI-6351
the
scanning beam. The video has been
clipped
at the point shown by the dotted
line
in
Sketch A
(1).
The output of Q7
appears like
that shown in Sketch A (2)
at the emitter and in Sketch A (3) at the
collector.
The emitter output is coupled
to the base of Q10. The collectors of Q9,
Q10, and Q11
are common and have a
common load. Therefore, any signal that
appears at the bases of these transistors
is
mixed as a single common output as
shown in Sketch A (4). The collector out-
put of Q7 is delayed by L2 -L7, etc.,
an
amount equal
to
the delay
of
Q8. This
delay is equal to the maximum rise time
of
the
video pulses. This delayed video
is
applied to the base of Q11 and is also
given a rising frequency response by C19
on the base of Q11. It results in the pulse
shown in Sketch A (5). The network on the
emitter of Q10 (L15 and C18) boosts the
high frequencies, which results in the pulse
shown in Sketch A (6).
It can be seen that when all of these are
added in the common collector circuits, the
looks like that shown in Sketch
A (7). The consequence is an increase in
rise time of the video, which gives an in-
crease in apparent resolution. This com-
bined output is applied to the feedback stages,
Q12 and Q13.
R25 is used to adjust the amount of aper-
ture correction, and R31 is used to adjust
the balance between the leading and trailing
edge correction.
A sample of the video is rectified by the
peak -to -peak detector, CR5 and CR6, to pro-
duce a d -c voltage proportional to the video
level. This voltage is applied to the video
level meter.
Chrominance Video Amplifier Board,
PL -7674505
Refer to the Waveforms, Figs. 22 and 23,
the Printed Circuit Diagram, Fig. 24, and
the Schematic Diagram, Fig. 25.
It
should be noted that there are three
identical video
amplifier
circuits on the
chrominance video amplifier board. The cir-
cuit analysis that follows applies to the red
chrominance video amplifier. The blue and
green amplifiers are the same, except that
the blue amplifier uses the 200 -series and
the green amplifier the 300 -series of com-
ponent numbers.
The input circuit of the chrominance video
amplifier provides
a
75 -ohm termination
impedance for the preamplifier board and a
level setting potentiometer for the succeeding
stages. A voltage gain of 10 is realized in
the first stage, 0101, which represents the
major part of the gain of the amplifier. An
emitter follower, Q102, furnishes the buf-
fering for the clamped stage, Q104, while
Q103 is the squasher/clamp. A phase in-
verter, Q106, precedes the feedback stage,
Q107 and Q108. The nominal output voltage
of Q108
is
0.7
volt peak -to -peak, when
properly terminated. A peak -to -peak detector
using diodes CR103 and CR104 is employed
at the output to provide a d -c voltage which
is proportional to the video for video meter-
ing.
Timing and Calibration Generator
Board, PL -7674517
Refer to the Waveforms, Figs. 26 through
28, the Printed Circuit Diagram, Fig. 29, and
the Schematic Diagram, Fig. 30.
This board contains circuits for several
different functions.
It generates a squash
pulse, a power supply trigger pulse, a cali-
bration sawtooth, and a buffered 15 -kHz sine
wave for other boards. The board also in-
cludes the circuit for the Camera tally lights.
Q8 and Q9 are common emitter stages
which amplify and shape the horizontal blank-
ing pulses. These pulses are used to drive
Q10. a ringing circuit. The ringingfrequency
is determined by L3 and C31. CR6 is
a
damper diode used to clip the negative half
of the cycle. CR8 and CR19 further clip the
remaining half sine wave to form a pulse.
Q11 is a phase splitter. The negative pulse
(collector) is used as the squash pulse, and
the positive (emitter) is differentiated and
then amplified by Q14 and used as the Camera
power supply trigger. A second output from
Q11 is fed to Q1.
Q1 and Q2 are used to generate a sawtooth
wave shape. The pulses from Q11 are applied
to the base of Ql, which is normally turned
19