Heathkit IG-4505 - Page 39

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Page 39
Since the components in most oscilloscope vertical input
attenuators have a rather long time constant (as compared to
the vertical amplifier circuits), use a lower frequency square
wave signal (1 ms) to make vertical attenuator compensation
adjustments. Also, an adjustable amplitude signal is needed
for
the
various
attenuator
ranges,
especially
the
highly
attenuated ranges. Therefore, use the 1 ms (1000 Hz)
VOLTS
OUT
signal
from
the
Calibrator
when
you
make
vertical attenuator compensation adjustments.
When
you
make
vertical
attenuator
compensation
adjustments
on
an
oscilloscope,
set
the
TIME
OUT
switch
to
IN CASE OF
This
part
of
the
Manual
provides
you
with
information
that
will
help
you
locate
and
correct
difficulties
which
might
occur
in
your
Oscilloscope
Calibrator.
This
information
is
divided
in
various
sections.
The
first
section,
“General,”
contains
suggestions
of
a
general
nature
in
the
following
areas:
Visual check and inspection.
Precautions to observe when bench testing.
the
1
ms
position
and
the
MULTIPLIER
switch
to
X1.
Set
the
VOLTS
OUT
switch
to
obtain
a
trace
approximately
4-5
cm
high.
You
will
encounter
one
of
three
waveforms.
Parts
A,
B,
and
C
of
Figure
2-5
show
the
conditions
of
too
much
compensation,
too
little
compensation,
and
the
correct
amount
of
compensation
respectively.
Adjust
the
appropriate
trimmer
capacitors
in
the
vertical
attenuator
to
obtain
the
waveform
shown
in
Part
C,
NOTE:
Make
sure
the
oscilloscope
vertical
gain
is
in
its
calibrated
position
when
you
make
vertical
attenuator
compensation
adjustments.
DIFFICULTY
The
second
section,
“Troubleshooting,”
contains
a
series
of
three
test
charts:
TEST #1 —
inoperative.
If the Calibrator is completely
TEST #2 — If the TIME OUT function is inoperative.
TEST #3 — If the VOLTS OUT function is
inoperative.
Start your troubleshooting procedure by first reading the
following
‘General’
section.
Then
proceed
to
the
appropriate Test.
General
Visual Checks
1. About 90% of the kits that are returned for repair do
not function properly due to poor soldering.
Therefore, you can eliminate many troubles by a
careful inspection of connections to make sure they
are soldered as described in the Soldering section of
the “Kit Builders Guide.” Reheat any doubtful
connections and be sure all the wires are soldered at
places where several wires are connected. Check
carefully for solder bridges between circuit board foils.
2.
Check
to
be
sure
that
all
transistors
are
in
their
proper
locations,
and
are
installed
correctly.
3.
Check
the
value
of
each
part.
Be
sure
that
the
proper
part
has
been
wired
into
the
circuit,
as
shown
in
the
Pictorial
diagrams
and
as
called
out
in
the
wiring
instructions.
It
would
be
easy,
for
example,
to
install
a
2200
92
(red-red-red)
resistor
in
a
step
that
calls
for
a
220
22
(red-red-brown)
resistor.