Wavetek 142 Instruction Manual page 24

13.
With
FREQ
DIAL
still
fully
clockwise, set the voltage 26.
Adjust
R165
for a 2.5
V
p-p signal
output from
the
between
IC2(2)
and ground
(at
R95)
to
0
Vdc
sine
amplifier
±25 mV.
±100
/iV,
using
R93.
14.
Set
FREQ
DIAL
to
1
and
adjust voltage
between
TP6
and
TP7
to 0
Vdc ±200
juV, using
R129.
15.
Adjust voltage
between
TPS
and
TP9
to
0
Vdc
±200
juV,
using
R
1
32.
4.2.5
Triangle
Amplitude Adjustment
16.
Set
FREQ HZ
to
X
100,
FREQ
DIAL
to
10,
WAVE-
FQRM
SELECTOR
to
TRIANGLE,
and
SYMMETRY
to
NORM.
17.
Connect
the oscilloscope
probe
(a
type
W
or
1A5
plug-in
module should be used with the scope)
to
\
position of the
WAVEFORM
selector switch,
SW2,
see Figure 4-4.
18.
Adjust the
triangle
amplitude to
±1.25
V
±5
mV,
using
R12
and R23,
see
Drawing
142-010.
4.2.6
Sine Distortion
Figure 4-1
-
Distortion Analysis Test Set-Up
19.
Set
FREQ
HZ
to
X
100,
VERNIER
to
CAL,
WAVE-
FORM
SELECTOR
to
SINE,
FREQ
DIAL
to
10,
and
OUTPUT ATTEN
to
0
dB.
20.
Set
30
V
P-P
MAX
control
to
3/4ths of
full
CW,
and connect
oscilloscope
probe
to position of
the
WAVEFORM
selector
switch (SW2),
see
Figure
4-4.
27. Readjust
R153
so that the
dc
offset of the
sine
amplifier
is
0
V
±5 mV.
28.
Connect
the
Spectrum Analyzer
as
shown
in
Figure
4-2,
and check
the sine
wave
distortion at frequencies
higher than
600 kHz.
If
distortion
does not meet
the
specification,
check
calibration
of C95, follow proce-
dure
4.2.10.
21.
Adjust
R153
so that the dc offset of
the
sine ampli-
fier
is
zero.
22.
Connect
the
test
equipment
as
shown
in
Figure
4-1,
and
adjust
R159, R168, and
R145
for
minimum
sine
wave
distortion.
23. Set
FREQ
HZ
to
X IK
and
readjust
R159, R168,
and
R145
for
optimum
sine distortion.
24. Set
FREQ HZ
to
X
100 and
readjust
R159, R168,
and
R145
if
necessary
25. Alternately
perform
steps
24 and 25
until
the
least
amount
of
sine
wave
distortion
is
obtained
on
both
ranges
—
typically
.14%.
4.2.7
Frequency
Calibration
29.
Set
FREQ HZ
to
X10K,
FREQ
DIAL
to
10,
VERNIER
to
CAL,
and
adjust
R269
to
obtain
100 kHz ±100
Hz.
MODEL
142
HP
141S
50-OHM
TERM.
50J2OUTO-
-O
INPUT
Figure 4-2
-
Spectrum Analysis Test Set-Up
4-3
12/71