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Heathkit IO-4550 - Page 35

Heathkit IO-4550
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Q
Geum
Arrsrcire
Disconnect
the
1
MHz
square
wave
signal
from
the
Y1
INPUT
connector.
7.
Connect
a
1
MHz
square
wave
signal
to
the
Y2
INPUT
connector.
8.
Position
the
trace
as
shown
in
Figure
22.
Then
adjust
trimmer
C118-2
so
the
top
of
the
peak
is
no
more
than
4
mm
from
the
bottom
of
the
dip.
9.
Disconnect
the
1
MHz
square
wave
signal.
POSITION
(OFF).
10.
Turn
the
Y2
counterclockwise
control
fully
This
completes
the
‘Calibration’
of
your
Oscilloscope
unless
you
have
a
low
capacitance
(X10)
probe.
Proceed
to
“Touch
Up
Adjustments”
if
you
do
not
have
such
a
probe.
If
you
do,
perform
the
following
steps.
LOW
CAPACITANCE
PROBE
Perform
the
following
steps
only
if
you
have
a
low
Capacitance
(X10)
probe
that
will
compensate
to
approximately
40
pF
(35-47
pF).
Probe
Compensation
and
Amplifier
Equalization
This
adjustment
procedure
equalizes
the
input
capacitance
of
both
vertical
amplifiers
so
a
low
capacitance
probe
can
be
used
on
either
channel
without
the
need
to
recompensate.
If
you
have
two
probes,
set
one
of
them
aside
temporarily.
Perform
the
following
adjustments
using
one
probe.
Then
connect
the
other
probe
and
adjust
only
the
probe
trimmer
for
the
proper
amount
of
compensation.
1.
Set
the
indicated
front
panel controls
as
follows:
Y1:
VOLTS/CM
10
mV
POSITION
Center
the
trace
on
the
screen.
INPUT
switch
AC
TIME/CM
.2mS
TRIG
Y1,+
Page
33
2.
Connect
the
low
capacitance
probe
to
the
Y1
INPUT
connector.
3.
Connect
the
probe
end
to
a
1000
Hz
square
wave
signal.
Adjust
the
amplitude
of
this
signal
for
a
4-5
cm
display.
4.
Adjust
the
probe
trimmer
for
the
proper
amount
of
compensation
as
shown
in
Part
C
of
Figure
21.
Do
not
try
to
obtain
the
ultimate
adjustment
at
this
time.
NOTE:
The
trimmer
capacitors
called
out
in
the
following
steps
are
on
the
vertical
circuit
board.
5.
Adjust
the
Y1
input
trimmer
capacitor
C111-1
(+
1)
to
obtain
the
maximum
amount
of
overshoot
on
the
leading
edge
of
the
waveform
as
shown
in
Part
A
of
Figure
21.
This
adjustment
sets
the
Y1
input
trimmer
capacitor
at
minimum
capacitance.
6.
Readjust
the
probe
trimmer
for
the
correct
amount
of
compensation.
7
Disconnect
the
probe
from
the
Y1
INPUT
connector
and
connect
it
to
the
Y2
INPUT
connector.
8.
Set
the
indicated
front
panel
controls
as
follows:
Y1:
POSITION
Fully
counterclockwise
(OFF)
Y2:
POSITION
Center
the
trace
on
the
screen.
VOLTS/CM
10
mV
(or
20
mV
or
50
mV
if
necessary)
INPUT
switch
AC
TRIG
Y2,+

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