Sequence Length; Troubleshooting Chart - Wavetek 132 Instruction Manual

Digital
Noise Amplitude
Symmetry
\/
1.
Set function
selector to _JU
[_,
NOISE
FREQ
HZ
selector to
160 kHz, and depress
SEQUENCE
LENGTH -
215
-
1
push button.
2.
Connect
oscilloscope,
with peak
mV
plug-in, to
location
DN
on
digital
board.
3.
Adjust R36,
using
comparator,
to provide
a
positive
peak
of
+1.25
V
±10
mV.
4.
Adjust R39,
using
comparator,
to
provide
a
negative peak of
—1.25
V
±10 mV.
Analog
Noise
Amplitude
Symmetry
1.
Connect
BNC
cable to
NOISE
SYNC
connector
(rear panel)
and sync connector on
oscilloscope.
2.
Depress
SEQUENCE LENGTH -
2
1S
-
1
push
button.
3.
Connect
oscilloscope to location
AN
on
digital
board.
4.
Adjust
R22
(gain)
and
R23
(balance) to provide
a
2.5
V
p-p
signal
centered about ground.
S/N Frequency Compensation \/
1.
Set function
selector to
Hj
.
2.
Depress
MODE
—
S/N
push
button.
3.
Set
frequency
dial
to 1.0
and
FREQ HZ
selector
to
X100K
(100
kHz).
4.
Set
S/N
—
N/S
(dB) selector to
+50
position
and turn
vernier to
+9
position to provide
ap-
proximately +59
dB.
5.
Turn
OUTPUT VERNIER
(dB)
full
cw.
6.
Connect
oscilloscope to 50^2
OUT
connector
with 5012 terminator
(
n
u
function).
7.
Adjust
C5 on
analog board
for a slightly
peaked
square
wave
response,
as illustrated below.
8.
Remove
power from
unit.
9.
Remove
material insulating
BNC
connectors
from main
board.
10.
Lower
logic
board and
align holes
in
side
of
board with screw
holes.
11.
Install
two
side
screws
to secure
logic
board.
12.
Install
both
2
y
2
" standoff
screws
at rear
of
logic
board.
13.
I
nstall
cover
on
unit.
TROUBLESHOOTING
Basic
Techniques
Troubleshooting
the
Model 132
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
securely connected
to
the correct connector.
3.
Perform
the
checkout
procedure.
Many
out-of-
specification indications can be corrected by
performing
specific calibration procedures.
4.
Visually
check
the
interior
of the instrument.
Look
for such
indications as
broken
wires,
charred components,
loose
leads, etc.
Troubleshooting Chart
Table 4-2 provides a
list
of possible malfunction symp-
toms,
their
probable
causes,
and
the prescribed
reme-
dies.
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
re-
moving
the interaction.
The
basic units of the loop
can then be
tested individually.
The
following
step-bv-
step
procedure
describes
how
this
is
done. (The
genera-
tor
loop
is
all
contained
on
the
main
board.)
Consult
the next paragraph
for
removal
of cover and
panels.
1.
Set instrument controls
for
20
V
p-p,
2
kHz
sine-wave output.
16