and
in
the
PRESET
position
of
the
STABILITY
control.
It
is
adjusted so
that the
free-running
trigger multivibrator
will
trigger
the
main
sweep
multivibrator,
but
will
not
allow
the
main
sweep
multivibrator
to free-run.
a.
Turn
the
red
TRIGGER
SELECTOR
knob
to
AUTO.
b.
Disconnect
any
signal
source
that
may
be
connected
to
the
INPUT
connector.
c.
Advance
the
Preset
Stability
adjustment
until
a
trace
appears on
the
crt.
Note
the
position of
the
screwdriver
slot.
d. Advance
the
Preset
Stability adjustment
further
until
the
trace
brightens.
Note
the
position
of
the
screwdriver
slot.
e.
Retard
the
Preset
Stability
adjustment
to a
point
midway
between
the
positions
found
in
parts
3-c
and 3-d.
Time-Base
Circuit Adjustments
The
time-base
circuits
of
the
Type
515/515A
are
quite
stable
and should
not
require fre-
quenty
readjustments.
The need
for
readjust
ment
can
be
determined
quickly
by
checking
the
time-base
calibration
with an
accurate
time-mark generator.
Often
only
a
single
adjust
ment
need
be
made.
We
check
our
time
base
with
a
Tektronix
Type 180A or
181
Time-Mark
Generator.
How
ever,
you
can
use
any
other
frequency
generator
accurate
to
one
per
cent
or
better.
Because
the
small
amount
of non-linearity
present
in
the
time base
is
concentrated
in
the
first
and
last
centimeters,
we
adjust
the
timing
over
the
center 8
centimeters of the
display.
In
this
way
the
errors
are
minimized
and
the
accuracy
over
the
center
portion
can
approach
a
value
limited
principally
by
the
spot
size.
The
following
procedure
is
based
on
that
used
in
our
test
department.
This
sequence
should
be
followed.
1.
Magnifier
Timing
Adjustment
The
Mag.
Gain
Adj.
control,
R259,
adjusts
the
gain
of
the
horizontal
amplifier
to
calibrate
the
time-base
ranges with
the
magnifier
on.
a.
Set
the
T1ME/CM
controls
to
1
MILLISEC,
CALIBRATED.
(VARIABLE
clockwise.)
b.
Display
100
-microsecond
markers.
c.
Center
the
trace
with
the
HORIZONTAL
POSITIONING
control.
d.
Set
the
HORIZ. DISPLAY
switch
to
MAG.
e.
Adjust
the
Mag.
Gain
Adj.
control,located
over
the
neck
of
the
crt, so
that every
second
marker
corresponds
with
a
graticule line.
2. Normal-Sweep Timing
Adjustment
The
Horiz.
Gain
Adj.
control,
R225,
adjusts
the
amount
of
feedback
in
the horizontal
amplifier
to calibrate
the
time-base ranges
in
the
NORM,
position
of
the
HORIZ.
DISPLAY
switch.
a.
Display 1-millisecond
markers
with
the
TIME/CM
controls
set at
1
MILLISEC,
CALIBRATED.
b.
Set
the
HORIZ.
DISPLAY switch
to
NORM.
c.
Adjust
the
Horiz.
Gain
Adj.
control,
located
on the HORIZ. DISPLAY
switch just
above
the
power
trnasformer,
so the
markers
correspond
with
the
graticule.
3.
Sawtooth Amplitude
Adjustment
The
Sawtooth
Amplitude
control,
located
in
the top
row
of
controls,
provides
a
means
of
setting
the
sweep
length
so
it
fills
the graticule
without
hitting
the
sides of
the
crt
attendant
electron
scattering.
a.
Set
the
Sawtooth
Amplitude
control so
the
sweep
is about
10
1/2
centimeters
long.
4.
Mag
Registration
The
Mag.
Regis, control,
located
in
the
top
row
of
controls,
adjusts
the
voltage
on
the
feed-back
network
so
the
magnifier
expands
the
trace
both
ways from
screen
center.
a.
Back
the
STABILITY
control
off
to stop
the
sweep.
b.
Turn
up
the
INTENSITY
control
so the
spot
is
visible.
AA
Recalibration
Procedure
- Type
515/515A
5-5