Service Model 8901B
Option Combination
032
and
037
033
and
037
035
and
037
032
and
033
032
and
035
033
and
035
7. Key in 0.3D3 SPCL to select channel
2.
Set the signal source frequency
to
455 kHz then fine
tune the source to peak the signal on the oscilloscope. (Filter passband ripple can be as high
as
2
dB.
Find the highest peak of the ripple.) The 455 kHz waveform on the oscilloscope should have
an
amplitude between
4
and 7 divisions peak-to-peak.
If
faulty, see Service Sheet
33
and check
the circuits of channel
2.
8. Set the oscilloscope gain for a display of 6 divisions peak-to-peak. Increase the signal source
frequency until the waveform drops to 3 divisions peak-to-peak. Record the signal source’s
frequency.
9.
Decrease the signal source frequency until the waveform rises to 6 divisions peak-to-peak then
drops to
3
divisions peak-to-peak. Note the signal source’s frequency. The difference between this
frequency and the frequency in step
8
should be
as
indicated in Table 8D-12. If faulty, see Service
Sheet 33 and check the
First
Channel
2
Filter.
Frequency Difference Limits
(kHz)
3.0 7.0
Maximum
Minimum
6.4 10.4
12.4
16.9
mble
80-12.
Bandwidth
of
First Channel
2
Filter,
(J;I>
Step
9
10. Key in 23.1 to switch the LO
to
external. The EXT LO indicator on A72 should go on and the
LO input switch should make an audible click. If faulty, see Service Sheet 33 and check the LO
Input Switch (S4) Control.
(J8)
IF
Amplifier/Detector
Check
(Option Series
030)
(2374A
to
2636A)
1.
Set the signal generator
or
audio synthesizer to between 454
and
456 kHz CW at -70
dBm
(70.7
pVrms into
50R).
Connect
its
RF output to A54J2
(IF
IN) on the Modulation Analyzer.
2.
Connect a high-impedance, ac coupled oscilloscope to A54J1
(TEST
JACK).
3. Press the blue key, then press INSTR PRESET (the AUTOMATIC OPERATION key) to preset
the instrument. Key in 0.577 SPCL and 0.2E7 SPCL to switch in maximum
IF
gain and select
the Second Channel
1
Filter. Fine tune the signal source
to
peak the signal on the oscilloscope.
(Filter passband ripple can be as high as
2
dB.
Find the highest peak of the ripple.) The 455
kHz waveform on the oscilloscope should have an amplitude between
1
and
2
Vpp.
If
faulty, see
Service Sheet 7 and check the circuits of channel
1.
4.
Key in 50.6 SPCL to read the
IF
with the
IF
RMS
Detector. Calculate
reading
of
step
3
x
1.63.
The Modulation Analyzer’s display should read within
10%
of the calculated value.
If
faulty, see
Service Sheet 7 and check the
IF
RMS Detector.
5.
Set the signal source level for a Modulation Analyzer display of
2.00.
6,
Key in the Direct Control Special Functions listed in Table
8-13
followed each time by 50.6 SPCL.
For
each setting, the Modulation Analyzer’s display should be
as
indicated.
If
faulty, see Service
Sheet 7 and check the corresponding attenuator.
8D-34 Service Sheet BD3
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