Troubleshooting Chart - Wavetek 130 Instruction Manual

6.
Adjust
R126
and
R127
for
minimum
sine distor-
tion (see
photo).
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7.
Set
FREQ HZ
selector
by
X10K.
8.
Repeat Step 6 to obtain
least
distortion at
both
XI K and
X10K
ranges.
9.
Repeat Steps 3 and
4.
10.
Connect spectrum analyzer to unit
and check
sine
distortion
at
2
MHz.
TROUBLESHOOTING
Basic
Techniques
Troubleshooting the
Model 130
requires
no
special
technique. Listed
below
are a
few reminders
of basic
electronics fault isolation.
1.
Check
control
settings carefully.
Many
times an
incorrect control
setting,
or
a
knob
that has
loosened
on
its
shaft, will
cause a false indication
of
a
malfunction.
2.
Check
associated
equipment connections.
Make
sure that
all
connections
are
properly
connected
to the correct connector.
3.
Visually
check
the interior
of
the instrument.
Look
for
such
indications as
broken
wires,
charred
components,
loose
leads, etc.
4.
Perform
the
checkout procedure.
Many
out-of-
specification indications
can be corrected
by
per-
forming
specific calibration
procedures.
T
roubleshooting Chart
Table
4-2 provides a
list
of possible
malfunction
symptoms,
their
probable
causes,
and the prescribed
remedies.
Also
listed in this
table are
the
test
points
at
which measurements are to be
made
and the
para-
meter tolerances
at
these points.
To
use the trouble-
shooting
chart, locate
the
symptom
listed in
Column
1
and
follow the corresponding procedures. Localize the
fault to a
specific stage
by checking the parameters
given for
the major
test
points then,
check
the
dc
operating voltages
at
the pins of solid-state devices.
Check
associated passive
elements with
a
high input
impedance
ohmmeter
(power
off)
before replacing a
suspected
semiconductor element.
Troubleshooting Hints
The
interactive
nature of
a
closed loop presents a
somewhat
special
problem
when approached from
a
troubleshooting
standpoint.
The
simplest
way
to
reduce
problem complexity
is
to
open
the loop,
thereby removing the interaction.
The
basic units of
the loop can then be tested individually.
The
follow-
ing
step-by-step
procedure describes
how
this
is
done.
1.
Set instrument controls for
20
V
p-p,
2
kHz
sine-
wave
output.
2.
Check
at
coaxial-wire lug
of function selector
switch for
a
2.5
V
p-p square wave.
If
normal,
check output amplifier
(034-040).
3.
Unsolder and
lift
the
end
of
R51 (TP7).
This
is
the
output
of
the
integrator
and input to the
hysteresis switch.
The
generator loop has
now
been
opened.
4.
Inject
a 2.5
V
p-p
triangle
waveform
into
the
hysteresis
switch input
lead
(TP7).
5.
Check
at
the coaxial-wire lug
of the function
selector
switch for a 2.5
V
p-p
square wave
at
the
injected
frequency.
a. If
present, hysteresis
and output switches
are
okay. Proceed to Step
6.
b. If
abnormal, check
06-016
stages.
6.
Vary frequency
dial
from
ccw
to
cw
while observ-
ing
TP1
1
with
a
scope. Voltage
at this
point
should
remain
at
0
volts
throughout
dial rotation. If a
voltage variation
is
observed,
check
IC1
stage.
7.
Vary frequency
dial
from ccw
to
cw
while observ-
ing
TP4. Voltage reading should vary
from 0
to
approximately
—6
volts. If
voltage
does
not vary,
check IC2 stage
and
IC1 stage.
8.
Vary frequency dial
from ccw
to
cw
while observ-
ing
TP9. Voltage reading should remain
at
0
volts.
If
voltage varies
check IC3
stage.
9.
Vary frequency
dial
from ccw
to
cw
while ob-
serving
TP10. Voltage should vary
from
0
volts
to
approximately
+6
volts.
If
voltage
does
not vary,
check IC2 stage
and
IC1 stage.
10.
Vary frequency
dial
from ccw
to
cw
while observ-
ing
TPS. Voltage reading should
remain
at
0
volts. If
voltage varies,
check IC4 and IC5
stages.
1 1
.
Re-install
R51
Removal
of
Front and Back Panels
1,
To
gain access to
any part
mounted on bracket
assembly behind
rear panel,
proceed as follows:
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