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SECTION
8
CIRCUIT
DESCRIPTION
8-1.
VIDEO CIRCUIT
Q707, Q102
Q103, Q104
Q106
0201, Q202
low-pass
pre-
filter
emphasis
D101, D102
Q107,D104
Q108, Q109
frequency
modulator
detector
Q221, Q223
Oo
pb head amp.
ro i
0224, Q226
Q227 |
.
:
ne
ae
V1 (video) board
We Rote oom soe
Q301, Q302
Q303
0310
T7301
differ-
rf amp.
limiter
.
entiator
FL301, Q312
int
"
de-
integrator
7
ss
emphasis
Q313, Q314
Q315
REC
MN,
output
O
° PB
amp.
|
Fig. 8-1
Video system, block diagram
Video input and
The input video signal amplitude
monitor
output.
Since
the
AGC
is held
constant
by
an
AGC
Q101 and Q102
Low-pass filter
L101, L102,
C107
Video amplifier
Q103 and Q104
system.
Output
from
Q104
is
sampled and detected by D101
and D102
in order to control
the conduction
of FET
Q101.
Q101 acts as a variable resistor.
The 4.43 MHz
color sub-carrier,
5.5 MHz sound carrier and other
high frequency components
are
removed by this filter.
The amplified video is supplied
to three outputs, the FM mod-
ulator,
AGC
detector,
and
Clamp
D103, C112
Differential
amplifier
Q105 and Q106
Pre-em phasis
AV-3420CE has no E-to-E mode,
teocrd
video
is monitored
at
the
output
of
Qi04.
The video
signal is clamped
by
this
circuit.
The video signal, including the
d-c
level,
is amplified
by the
differential
amplifier
with
pre-
emphasis provided for high fre-
C114, R121, R122
quencies.
White clip
D104
D104
clips
the
white
peaks
(overshoot)
produced
by
the
pre-emphasis network.
8-1
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