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Channel
|
Control
Circuits
The
VAR
ATTEN
BAL
control
sets
the
base
DC
level
of
the
undriven
side
of
the
paraphase
amplifier.
This
control
is adjusted
for
no
trace
shift
as
the
VARIABLE
is
rotated.
The
setting
of
the
VAR
ATTEN
BAL
pot
is
specified
at
90°
from
center
(+1.7v
+.6v).
If
the
nuvistor
bias
is
too
far
from
design
center,
the
VAR
ATTEN
BAL
pot
can
not
make
this
spec.
The
coaxial
leads
to
the
VAR ATTEN
BAL
pot
are
used
to
keep
spurious
signals
out
of
the
paraphase
amplifier.
C159
is a high
fre-
quency
bypass
cap.
R159
is
used
to present
a
resistive
load
to
the
base
of
the
undriven
side
of
the
paraphase
amplifier.
The
PULL
TO
INVERT
sw and
the
POSITION
control
are
tied
across
the
collector
circuit
of
the
paraphase
amplifier.
The
PULL
TO
INVERT
sw
provides
a
180°
phase
inversion
of
the
current
drive
to
the
output
amplifier.
The
only
difference
in
the
Channel
1 and
Channel
2 circuits
is
the
operation
of
the
Channel
2 POSITION
control.
The
MODE
sw disconnects
the
Channel
2 POSITION
control in the
added
mode.
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