Tektronix SC 501 User Manual

Servicing
Information-
SC
501
INPUT
AND
VERTICAL
AMPLIFIER
CIRCUIT
DESCRIPTION
Input
Attenuator.
The input attenuators
allow
a
choice
of
either XI.
X10,
or X100
attenuation
of the input
signal,
which
is ac- or
dc-coupled
by
the
selected
position of SI 00.
C112
and
C104
allow the
XIO
and
X100
attenuation
networks to
be
frequency compensated. C117,
C110,
and
Cl 02
allow the
attenuation
networks
to
be normalized
for
a
time
constant
of
47 microseconds.
Preamplifier. The
preamplifier stage
employs a
dual field
effect
transistor.
Q120,
to
provide
a
high input
impedance.
Q120B
acts as a
constant-current source
for
Q120A.
Q125
and Q135
circuitry
operates as a
paraphase
amplifier. Q148
and
Q160
operate as
emitter-followers to
provide a
low-
impredance drive to
the
following stages.
Quiescently,
the
two
sides of the
paraphase
amplifier are
balanced
by
the
adjustment of R142 so
that there is no
current
through
the
gain-setting
resistor, R129,
when
the VARIABLE
control
is
fully
clockwise.
The input stages
are
diode clampred by
CR121
and
CR125,
protecting
the input stages
against
negative-going
over-drive
signals.
R130
(VARIABLE
con-
trol)
provides an adjustable
attenuation
factor other than
the
fixed
calibrated values set by
the input attenuators
and
the XI
position
of
R130.
Output
Amplifier. A
push-pull
signal is developed
at
the
emitters of Q148
and
Q160,
along
with
a
dc positioning
voltage
from R145
(vertical POSITION
control). The
gain
of
the
push-pull
amplifier,
consisting
of
0150, 0158,
0167,
and
0176,
is controlled by
Gain
adjustment R172.
The
output
stage, 0165
and
0178,
with their associated
components
is
a
balanced
grounded-base
amplifier
circuit
which is
protected
from over-drive
signals
by
clamping
diodes, CR165
and
CR178.
Trigger Takeoff.
The
trigger takeoff
amplifier,
0184
and
0190,
with their
associated
components,
develops the
internal
signal
to
trigger
the
sweep
generator. The
gain of
this
stage is about
seven.

Tektronix SC 501 Specifications

General

Brand	Tektronix
Model	SC 501
Category	Test Equipment
Language	English