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Switch SlOl.
Connector Jl94 allows for loop-through
operation.
Input video signal is ac-coupled to the base of emitter-
follower QlOl by capacitor ClOl.
The output at the
emitter of @101 drives the GREEN channel contrast
control (VR101) on the PCB-VIDEO-SUB.
The individual
contrast controls allow matching the CRT color levels.
Emitter-follower Ql02 isolates the contrast control
from the following cicuitry.
3.3.2
Sync Separator
The green video signal is provided by Ql31, Ql32, Ql33
and Ql34.
DlOl is a clamper diode for de restoration.
The composite video signal is clamped by Dl03, and
applied to pin 9 (the non-inverting input) of
operational amplifier IC101 through an emitter-follower
Ql36, IC101 pin 10 (the inverting input) is referenced
to approx. +5.6V.
Therefore only the sync tip would
have an amplitude less than the reference (+5.6V)
causing IC101 (pin 7) to switch to negative going
output which is applied to sync switcher Ql40 and
sync mixer Ql38, Ql39.
When External Sync is applied, sync switcher Ql40
automatically kills the output of sync separator
IC101(7).
For Internal Sync, Ql40 is non-conducting,
and the composite sync singal is applied to sync
mixer, Ql39.
In external sync condition, composite
sync signal is applied to SYNC/HD input terminal,
Jl97, and sync signal is rectified by diodes, Dl07,
0108.
The rectified output voltage turn on the sync
switcher, Ql40, and composite sync signal from the
syrtc separator is shunted to ground through
resist~r,
Rl69.
3-5
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