-.
. -
:=-:::.
display
to
within
the
viewing area when pressed. A
schematic
of
the
Vertical
Output
Amplifier
circuit
is
shown
on
diagram 4
at
the
rear
of
this manual.
Delay Line
Delay Line D L400 provides
approximately
120
ns
delay
for
the
vertical signal
to
allow
the
Sweep
Generator
circuits
time
to
initiate a sweep
before
the
vertical signal reaches
the
vertical deflection plates
of
the
CRT. This allows
the
instrument
to
display
the
leading edge
of
the
signal
originating
the
trigger pulse
when
using internal triggering.
Output
Amplifier
U440
is
an integrated
circuit
amplifier stage
that
provides the final amplification for
the
vertical signal. R401
and R411 provide forward
termination
for
the
delay line.
The
components
connected
between
pins 2 and 4
of
U440
provide delay-line
compensation.
Components
connected
between pins
14
and
15
and
pins 7 and 8
of
U440
provide
thermal
compensation
for
the
stage. The BEAM FIND
switch, when pressed, reduces
the
dynamic
swing capa-
bilities
of
the
stage,
thereby
limiting
the
display
to
within
the display area
of
the
CRT.
A
AND
B
TRIGGER
GENERATORS
General
The Trigger
Generator
circuits
produce
trigger pulses
to
start
the
Sweep
Generator
circuits. These trigger pulses are
derived
either
from
the
internal trigger signal
from
the
vertical deflection
system,
an external signal
connected
to
the
external trigger
input
connectors,
or
a sample
of
the
line voltage applied
to
the
instrument.
Controls
are pro-
vided
in
each
circuit
to
select trigger level, slope, coupling,
and source. Since
the
A and B Trigger
Generator
circuits are
virtually
the
same,
only
the
A Trigger
Generator
circuit
action and
the
differences
between
the
A
and
B Trigger
Generator
circuits are explained. A
schematic
of
these
circuits
is
shown
on
diagram 5
at
the
back
of
this manual.
Trigger Source
The Trigger SOURCE switch
S610
selects
the
source
of
the
trigger signal.
The
sources available
to
the
A Trigger
Generator
circuit
are
the
signal(s) being displayed (NORM),
Channel 1
(CH
1), Channel 2
(CH
2), LINE,
and
EXT. The
EXT +
10
(A trigger
circuit
only)
position
provides
10
times
attenuation
for
the
external
trigger signal.
The
B
Trigger SOURCE switch does
not
have a LINE
or
an EXT
+
10
position,
but
has a
STARTS
AFTER
DELAY position.
Circuit Description-465
In
the
LINE
mode
of
triggering, a sample
of
the
power
line frequency
is
obtained
from
the
secondary
of
power
transformer
T1501
in
the
Low Voltage Power Supply
circuit.
To
prevent
unwanted
attenuation
of
the
trigger
signal by
the
LF
REJ circuit,
the
Trigger COUPLING
switches should
not
be in
the
LF REJ
mode
when
using line
voltage as a trigger source.
Trigger Coupling
The
Trigger COUPLING switches
offer
a means
of
accepting
or
rejecting certain
components
of
the
trigger
signal.
In
the
AC,
LF
REJ,
and
HF REJ
mode
of
trigger
coupling,
the
DC
component
of
the
trigger signal
is
blocked
by coupling capacitors
C612
or
C611.
Frequency
com-
ponents
below
about
60
Hz
are
attenuated
when
using
AC
or
HF REJ coupling
and
below
about
15
kHz when using
LF
REJ coupling. The higher
frequency
components
of
the
trigger signal are passed
without
attenuation.
In
the
HF
REJ
mode
of
trigger coupling,
the
high
frequency
com-
ponents
of
the
trigger signal (above
about
50
kHz) are
attenuated,
while
the
lower
frequency
components
are
passed
without
attenuation.
The
DC
mode
of
trigger
coupling passes
unattenuated
all
signals from
DC
to
100
MHz and above.
Input
Source Follower
Transistor
0622
is
an
FET
source
follower. It provides a
high
input
impedance (set primarily by
R616)
for
the
trigger signal and also provides isolation
between
the
Trigger
Generator
circuit
and
the
trigger signal source.
Diode
CR617
provides
input
protection
for
0622
if
excessively high
amplitude
negative-going
input
signals are
present.
0624
is
a high-impedance, relatively
constant,
current
source for
0622,
and provides a measure of
temperature
compensation
for
0622.
Paraphase Amplifier
U640
is
a paraphase amplifier stage
that
converts
the
single-ended
input
from
Source
Follower
0622
into
a
push-pull
output
applied
to
the
tunnel
diode
driver stage.
Trigger Level Centering
adjustment
R635
sets
the
level
at
pins
14
and
15
of
U640
so
that
the
display
is
correctly
triggered when
the
LEVEL
control
is
centered.
The
LEVEL
control
varies
the
level
at
pins
14
and
15
of
U640
to
select
the
point
on a trigger signal
where
triggering occurs.
The
slope
of
the
input
signal
that
triggers
the
Sweep
Generator
circuit
is
determined
by
the
setting
of
the
SLOPE switch
S630.
When
the
SLOPE switch
is
set
to
the
+
position,
the
output
signal
present
at
pin 8
of
U640
is
in
phase with
the
input
signal
and
the
output
signal
at
pin 9
is
3-9
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