GE 4PE350A3 Instructions Manual page 36

EBI-6351
COLOR CAMERA
drawing its power from a non -regulated
nominal 115 -volt d -c source.
The
differential
amplifier, Q8 and Q9,
provides a high degree of amplification to
voltage changes appearing on the +100 volt
bus. The correction signal necessary to re-
store the supply to
its original operating
condition is applied in the proper phase to
the base
of Q5 through emitter follower
Q6.
If the voltage drop across the one -ohm
resistor, R22, increases because of an over-
load and exceeds the threshold voltage set
by R26 by an amount that triggers unijunction
Q10, it triggers the SCR, Q7, which reduces
the voltage on the base of Q6 to zero and
turns off Q5 so that the voltage output is
zero.
To recycle the supply, it must first be
turned off. If the overload condition still
exists, the supply does not turn on until
the condition has been corrected.
Z1
is
a
flip-flop
2
to
1
microcircuit
counter operating from a 15,750 -hertz pulse.
The output from Z1 is applied to the base
of square wave generator Q11 at a 7.875
-
hertz rate. This allows power switching to
occur during the blanking interval of a nor-
mal broadcast television system.
Q11, Q1, and Q2 form a square wave os-
cillator with feedback from the base circuit
of power switching stages Q3 and Q4. The
power stage drives T2, whose secondary
winding provides several secondary volt-
ages. The voltages for use with constant
loads are rectified and filtered, whereas volt-
ages for varying loads have additional reg-
ulation through series type regulators. Q13,
Q14, and Q15 are the regulators for the
+20 volt circuit, and Q16 and Q17 are the
regulators for the -20 volt circuit.
Q12 and Q18 form a flip-flop
2
to
1
counter circuit triggered by a 60 -hertz ver-
tical drive signal. The output is a 30 -hertz
square wave which is applied to the Plumbi-
con tube beam focus electrode, aiding in
Plumbicon tube alignment.
Viewfinder Switcher Board, PL -7674431
Refer to the Waveforms, Figs. 44 and 45,
the Printed Circuit Diagram, Fig. 46, and the
Schematic Diagram, Fig. 47.
22
All video switching for the Camera view-
finder is accomplished by d -c controlled
diode switches, CR1 through CR6. The five
stages which make up the switcher are all
identical, as are the eight diode switching
networks.
Stages Q4 (luminance) and Q5 (auxiliary)
are emitter followers, while Q1 (red), Q2
(green), and Q3 (blue) are used as phase
splitting stages in order to obtain outputs
which are of opposite polarity°
Because of similarity between stages, only
the red circuit is analyzed. Diodes CR1 and
CR2 are
connected back-to-back between
the emitter of Q1 and the output bus which
terminates at J8-9. When a small voltage
is applied to the cathodes of CR1 and CR2,
through R41, the diode is in the off or non-
conducting state.
To obtain an output from the red circuit,
a negative voltage is applied to the cathodes
of CR1 and CR2, through R40, turning them
on. Once this occurs, an output is provided
from the emitter of Q1 which is in phase
with the signal on its base. This red signal
appears at J8 -R.
To display a color difference signal, such
as W -R, diodes CR3 and CR4 are turned on,
as are diodes CR13 and CR14. This allows
the phase -inverted collector output from Q1
(red) to appear at J8-12 and the in -phase
emitter output from Q4 to appear at J8 -M,
thereby providing the color difference signal,
W -R.
To obtain a display from all circuits si-
multaneously, namely WRBG, all four diode
pairs, CR1 through CR4, CR5 through CR8,
CR9 through CR12, and CR13 through CR16,
must be turned on.
A monitor output coaxial connector per-
mits a video output to be displayed at another
monitoring location.
Sync Adder Board, PL -7782689
Refer to Figs. 48 and 73.
The 60 -volt pulses from the viewfinder
sweep board are used in a combination iso-
lation
and mixing stage. The pulses are
decreased to approximately 3.0 volts by a
resistive divider and fed to the base of Q1.
Q1 is an emitter follower and low driving