Theory of Operation—
465B Service
DETAILED DESCRIPTION
CHANNEL 1 PREAMP
Introduction
The Channel
1
Preamplifier
circuit, shown in Figure
3-
2,
provides
control of input coupling, vertical deflection
factor, gain and
dc
balance. Input
signals
for vertical
deflection
on the crt are connected
to the
CH
1 OR
X
input
connector
When
the
TIME/DIV switch
is set to the X-Y
mode, theinput signal appliedtotheCH
1 ORXconnector
provides the horizontal (X-axis)
deflection
Input Coupling
Signals applied
to
the
input connector can
be
either
ac-
coupled or
dc-coupled or, they can be internally
dis-
connected from the input
to the Vertical Input Amplifier
stages. When Input Coupling
switch S30A is set for
dc
coupling, the input signal
is
coupled
directly to the Input
Attenuator
stage When ac coupled, the input
signal
passes through capacitor Cl 301
2 which prevents the
dc
component of
the input signal from passing to
the
:
C13012
CH 1 OR X
R 13010
S30A
INPUT
COUPLING
SWITCH
2ND
AMPLIFIER
STAGE &
TRIGGER
PICKOFF
01155,01355
Q1150.
Q104G
01240,01038
01346,
01384
Q1145
INPUT
ATTEN
*
2
.
*
10
.
^-
100
.
-A
VARIABLE
BALANCE
l
|
VOLTS/DIV
INPUT
SOURCE
FOLLOWER
Q1297A.B
EE3
POSITION
TO
VERTICAL
SWITCHING
CIRCUIT
FIRST
AMPLIFIER
STAGE
01175.01375
U1290
VERT SIG^N
EMITTER
FOLLOWER
01028
TRIGGER
SIGNAL
-
EMITTER
FOLLOWER
01125
HORIZ
SIGNAL
EMITTER
FOLLOWER
Q1004
TO
HORIZ
AMPL
TO
-
TRIGGER
GENERATORS
3-4
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