Tektronix SC 501 User Manual

Servicing
Information—
SC
501
LOW
VOLTAGE
SUPPLY
CIRCUIT
DESCRIPTION
The
+20
V
supply
provides power to
operate
the
SC
501
and
also
establishes
the
reference supply for
all
other
power
supplies,
including the crt
system. An error-
sensing
circuit,
Q500,
compares
a
sample of
the
+20
V
across
a
voltage
divider (R507-R506-R504)
with a
reference
voltage
established by
Zener diode,
VR500. Any
voltage
difference (or
change)
between
the base
and
emitter
of
Q500
is
amplified
by
Q500
and
applied to
the base of
Q510.
This
results in Q510
controlling (or regulating) the
conduction
of the
PNP
series-pass transistor
(located
in the
mainframe)
to
correct
for
a
change in the
+20
V
supply.
R500 (+20 V
Adjust)
sets
the quiescent
level at the base
of
Q500. R506
provides current
limiting for
Q500
in case
Q510
fails.
C505
prevents regulator
oscillations. Boot-
strapped
emitter-followers,
Q520
and
Q525
regulate the
+8.2
V supply in a
manner
similar
to
the
operation of
the
+20
V
regulator.
The
—20
V
and
—8.2
V
supplies are
regulated in
a
manner
similar
to
the
+20
V
and
+8.2
V
supplies,
except
that Q545
controls the conduction of
the NPN
series-pass
transistor located in the
mainframe. The
reference voltage
for the error-sensing circuit,
Q540,
is established by
CR540.

Tektronix SC 501 Specifications

General

Brand	Tektronix
Model	SC 501
Category	Test Equipment
Language	English