Theory
of
Operatlon-SC 502
pickoff
is
amplified
by
common
base
a
m
p
li
f
i
er
0720.0720
p
r
o
v
i
d
e
s
a
low
input
im
p
e
d
a
n
c
e and
isolationforthe
input
signal.
The gain
of
0720
is
d
e
t
er
m
i
n
e
d
by
the
size
of
the
c
o
l
l
e
c
to
r
resistor, which
includes
the
Ext
Horiz Gain
control
R723
and R725.
The
SECONOS/OIV
switch
in
the
AMP
position
also
causes
0710
to
be
forward
biased
and
0700
to be
reverse biased
to prevent
the
sweep
ramp
from
reaching
the
output
amplifier.
The
POSITION
control
is
connected
to the base
of
cu
r
r
e
n
t
source transistor 0730,
w
h
o
s
e
output
adj
usts
the
current being
fed
to the in
p
u
t
of the
output
amplifier.
DIAGRAM
<i>
CIRCUIT DESCRIPTION
Horizontal Amplifier
Output Amplifier. The
output
of
the
horizontal
preamplifier
is applied
to
the
b
a
s
e
of
0745.
0745
and
0765
comprise
an
e
m
i
tt
er coupled paraphase amplifier.
0
7
5
5
is
t
h
e current source for
t
h
e
paraphase
a
m
p
l
i
f
i
er
.
The
Centering
c
o
n
tr
o
l
,
R7SO
provides
a
means of
correcting
for
differential
u
n
b
a
l
a
n
c
e
in
the
amplifier
or
crt.
while
the
Sweep
Gain
control,
R770
sets
the
o
v
e
r
a
l
l
gain
of
the
h
o
r
iz
o
n
t
a
l
amplifier.
R7S0
and
R764
p
r
o
v
i
d
e thermal
compensation
for
the
paraphase
amplifier
stage.
Transistors
0775-0780-0785
and
0770-0795-0790
are
connected
as
two
se
p
a
r
a
t
e
current-driven
feedback
amplifiers.
I
n
p
u
t transistor
0775
(in
the
left
output
amplifier)
is
an
NPN
transistor
for
b
e
t
1er
response
to
positive-going
S
i
g
n
a
l
s
.
while
input
transistor
0770
(in
the
right
output
amplifier)
is
a
PNP
t
r
a
n
s
is
t
o
r
for
better
negative-going
si
g
n
a
l
response.
Negative feedback
is
p
r
o
v
i
d
e
d
from
the
collectors
of
output
transistors
0780-0785-0795-0790
to the
base
of
input
transistors
0775
and
0770
t
h
r
o
u
g
h
feedback
networks
C773-R773
and
C785-R789.
Capacitors
C775,
C776,
and
C791
are
speed-up
c
ap
a
c
it
o
rs
to improve
the
amplifier
response
to
fast chan
g
e
s
.
DIAGRAM
�
CIRCUIT
DESCRIPTION
Z-Axis Amplifier and Crt Circuit
The
crt
circuit
produces
the
high
v
o
lt
a
g
e
potenti
als and
p
r
o
vi
d
es the control
circuits
n
e
c
e
s
s
a
r
y
for operation
of
the
cathode-ray
t
u
b
e
(crt).
The
Z-Axis
amplifier
and
Blanking
a
m
p
li
f
i
e
r
circuits
a
r
e
included
with
the
crt
circuit
discus
sion, since
they
set
the
i
n
t
e
n
S
ity
of
the
crt
display.
Z-Axis Amplifier
The
Z-Axis
a
m
p
l
i
f
i
e
r
is
a
c
u
r
re
n
t driven,
s
hu
n
t
feedback
operational
a
mp
l
i
fi
e
r
with
a
voltage output.
The
am
pi
ifier
c
o
n
si
sts
of
0835. 0845,
and
0840.
The
feedback
path
is
from
the
0845-0840
collectors
through
C834-R834
to
the
summing
point
at the b
as
e
of
0835.0845
and
0840
are
connected
as
a
collector-coupled
complementary
amplifier that
p
r
o
v
i
d
e
s
a
f
a
s
t
linear
output
signal
while
consuming minimum
quiescent
power,
0845
acts
as
the
pull-up transistor
and
0840
acts as
the
pull-down
tran
sistor
for
the
a
m
pl
i
f
i
e
r
.
The o
u
t
p
u
t
voltage
from
the
amplifier
provides the drive signal
to
control
the
crt
intensity level through
the
control-grid supply.
3-6
The
output
voltage
level
of
the
Z-Axis amplifier
is
determined by
the
voltage
drop ac
r
o
s
s
R834 in
reference
to
the
voltage
level
at
the
s
u
mm
i
n
g
point
for
the
amplifier
(base
of
0835).
The current through
R834
is determined
by
the
input
current
from
a
combination
of
two
sources,
INTENSITY
control
and sweep
b
l
a
n
k
i
n
g.
CR841
and
current
limiting
r
e
s
i
s
t
o
r
R841
act
as
a
protection
circuit
for
the
Z-Axis
amplifier
in
c
a
s
e
of a
high-voltage
short.
0825
and
0830
form a
c
omp
a
r
a
t
or
with
the
sweep
blanking
signal
set1ing the
reference
level.
To
unblank
the
crt,
the
voltage
level
at
0830
b
a
s
e must be more positive
than
the
level at
the
base
of
0825.
Blanking Amplifier
A
co
m
b
i
n
a
t
i
o
n
of
four
d
i
f
f
e
r
e
n
t
input
Signals
control the
o
u
t
p
u
t
current
o
f
t
h
e
blanking
amplifier. These
signals
are:
sweep
unblanking, horizontal
amplifier
mode,
chop
blank
ing and
intenSify from
pin
19B
of
the
rear
interface
.
0800
and
0805
f
o
r
m a
comparator
circuit with
the base
of
0805
REV C APR 1980
Summary of Contents for SC 502
Page 1: ...SC 502 OSCILLOSCOPE ...
Page 2: ......
Page 9: ...SC 502 1878 1 The SC 502 Oscilloscope xi REV APR 1982 ...
Page 10: ...Verso Filler Page z z ...
Page 32: ...Verso Filler Page z z ...
Page 34: ...Verso Filler Page z z ...
Page 63: ...Section 6 SC 502 OPTIONS There are no options available at this time REV A APR 1980 6 1 ...
Page 84: ...Beam R873 C473 Ext Bal R535 CH 1 Vert Po R335 CH 2 Vert Pos R394 ADJUSTft TP980 5 ...
Page 125: ...REV MAR 1 984 ...
Page 126: ...SC 502 m m o ...
