Checks
and
Adjustments
Astigmatism Adjustment
1.
Obtain a display
as
described
in
"Initial Setup."
2.
Set 20 MHz BW LIMIT on and adjust the
CH
1 POSITION control
to
center
the display
on
the screen.
3. Select!1V and position the cursors near the top and bottom of the screen.
4.
Set SEC/DIV to 1
/lS.
5.
Slowly adjust the FOCUS control
to
its optimum setting (best defined
display
of
cursor dots).
6.
Use a small-bladed screwdriver to adjust the ASTIG control for best defined
display
of
cursor dots. The waveform and the entire readout should be
well-defined.
7. Since the ASTIG and FOCUS adjustments interact, repeat steps 5 and 6
until the best-defined display over the entire graticule area
is
obtained.
NOTE
Once
set,
the ASTIG adjustment should be correct for any display. How-
ever,
it
may be necessary to reset the FOCUS control slightly when the
INTENSITY control setting
is
changed.
Auto DC Balance Routine
4-2
The oscilloscope
can
automatically dc-balance Channel 1 and Channel
2.
This
routine minimizes trace shifts when adjusting the
VOL TS/DIV and VOL TS/DIV VAR
controls, and when switching Channel 2 between noninverted and inverted. This dc
balance remains valid
as
long
as
the instrument
is
operating within
5°C
of the
ambient temperature at which the routine was performed, provided the instrument
has
had
a 20-minute warm-up period.
To initiate the adjustment, press the upper, input-coupling buttons for both
Channel
1
and
Channel 2 at the same time. When the Auto
DC
Balance cycle
is
complete, the instrument will return to normal operation.
NOTE
If
a circuit defect prevents accurate dc balance, the routine halts and LIMIT
is
displayed. Press the upper Trigger COUPLING button to continue balanc-
ing
the
remainder
of
the circuitry.
If power to the instrument
is
interrupted before the balancing cycle
is
complete,
a
DC
balance error may
be
apparent
in
subsequent operation. When power
is
restored, restart the
DC
balance routine, after the instrument has warmed
up.
2465A/2455A/2445A Operators
To Next Page
Loading...
Need help?
General
