Heathkit IO-4550 - Page 34

Page 32
SQUARE WAVE COMPENSATION
Connect a 1 MHz square wave signal to the Y1 INPUT
connector.
Set the indicated front panel controls as follows:
TIME/CM .2uS
TRIG Yi,+
Yi:
INPUT switch AC
VARIABLE Fully clockwise (CAL)
VOLTS/CM As necessary to produce a display
similar to that shown in Figure 22.
POSITION Center the trace on the screen.
Y2:
INPUT switch GND
VARIABLE Fully clockwise (CAL)
VOLTS/CM Same as Y1, above
POSITION Fully counterclockwise (OFF)
Figure 22
NOTE:
In
the
following
step
you
will
be
instructed
to
adjust
=~
the
displayed
square
wave
for
a
certain
“overshoot.”
This
@
will
produce
the
widest
possible
bandwidth
for
your
Oscilloscope.
You
may
adjust
the
square
wave
for
a
flat
top.
However,
this
will
somewhat
reduce
your
Oscilloscope
bandwidth.
Nevertheless,
the
bandwidth
will
still
meet
specifications.
F
3.
Position
the
trace
as
shown
in
Figure
22,
with
the
VERT
POS
and
HORIZ
POS
controls.
The
bottom
of
the
dip
should
be
on
a
horizontal
graticule
line.
The
“overshoot”
peak
height will
vary
with
the
setting
of
C118,
the
high
frequency
compensation
trimmer
(on
the
vertical
circuit
board).
(Your
dip
may
not
look
like
the
one
shown.)
4. Adjust trimmer ©C118-1, with a nonmetallic
screwdriver, so the top of the peak is no more than 4
mm from the bottom of the dip. NOTE: If you have
trouble with this adjustment, check the two blue wires
connected to the CRT socket for proper positioning.
5. Set the indicated front panel controls as follows:
Y1:
INPUT switch GND
POSITION Fully counterclockwise (OFF) o>
Y2:
INPUT switch AC
POSITION Center trace on screen
TRIG Y¥2,+