ing
or
loss
of
frequency
response. If
you
use
unshielded leads
keep
them
as
short
as
possible.
Two
cables or
probes
can
be
connected
to
the
oscilloscope
at
once.
You
can
then
select
the signal
on
either
cable
with the
INPUT
SELECTOR switch.
However,
if
one
signal
is
very
much
larger
than
the other, some
crosstalk
may
occur
and
the
cable
having
the larger
signal
should
be disconnected.
Coupling
It
is sometimes
unnecessary
or
undesirable
to display
the
de
level
of the
waveform.
In
the
two
AC positions
of
the
INPUT
SELECTOR
switch,
a
capacitor in
series
with
the
input
blocks
the
de
component
of
the waveform so
that
only
the
ac
component
is displayed.
Deflection
Sensitivity
The
VOLTS/CM
switch
inserts
frequency-
compensated
attenuators
ahead
of the
amplifier.
The
VARIABLE
control
provides
continuous
adjustment of
the
deflection
sensitivity
between
the
values
indicated by
the
VOLTS/CM
switch.
The
VARIABLE
control must be
clockwise
against
the
stop
for
the
sensitivity
to
be
as
indicated
by
the
VOLTS/CM
switch. The
red
UNCALIBRATED
light
indicates when
the
VARIABLE
control
is
not
fully
clockwise.
DC
Balance
Adjustment
After
the
oscilloscope has
been
in
use
for
.
a
period
of
time
you
will
notice
that the
trace
will
change
position
as
the
VARIABLE
control
is
rotated.
This
is
caused
by
tube
aging
and
the
resultant
shift
in
operating
potentials.
To
correct
this
condition rotate
the
VARIABLE
control
back
and
forth and adjust the
DC
BAL
control
until
the
trace
position
is
no
longer
affected
by
rotation of
the
VARIABLE
control.
AUXILIARY FUNCTIONS
Square-Wave
Calibrator
The
square-wave
calibrator
provides
a
source
of
square
waves
of
known
amplitude
at
about
1000
cycles.
The
outout
impedance
varies
with
the
voltage
but
is
as
high
as
5,000
ohms.
Be
sure the
load
impedance
you
connect
to
the CAL. OUT
connector
does
not
change
the
output
voltage.
Trace-Brightness
Modulation
To
couple
markers
or
other
signals
into
the
ert
cathode
for brightness
information,
disconnect
the
ground
strap
at
the rear of
the
instrument
and
connect
the
signal
to the
CRT
CATH.
binding
post.
Graticule
Illumination
The
graticule lighting
control,
labeled
SCALE
ILLUM.,
can
be
adjusted
to
suit
the lighting
conditions
of
the
room.
The
graticule can
be
mounted
in
either
of
two positions
rotated
180
degrees
from each other.
In
one
position
the
illumination
is
colored
red
and,
in
the
other
position,
white.
The
white
will
reproduce
well photographically.
A
green
light
filter
is
supplied
which
can
be used
for
increased
contrast.
Normally
this
filter
should be
mounted
next to
the
ert
screen
so
it does
not
block
the
light
from
the graticule
lines.
Direct
Connection to
Deflection Plates
Connections
can
be
made
directly to the
deflection
plates
by
removing
the
cabinet
on
the
left
side.
The
two
pins
on
the
left-hand
side
of
the
ert
neck
are the
vertical
deflection
plates.
To
avoid
distortion,
the average
de
potential on
these
plates should
be between
150
and
200
volts.
Unless
de
coupling
is
required,
connect
coupling
capacitors in
series
with
the
leads
to
the
deflection
plates
and
connect
one-megohm
resistors
from
the
deflec
tion
plates
to the
leads
from
the
delay line.
With
this
connection
the
plates are
maintained
at the
proper
operating
potential
and
positioning
control
is
retained
by the
front-panel
controls.
2-10
Operating Instructions
-
Type
515/515A
AA