Model 8901B Service
Direct Control
Special Function
0.250
able
80-13.
Attenuation Stepping,
@
Step
6
Display Limits
Minimum Maximum
Attenuator
1
0.1
2
0.22
7.
8.
9.
10.
11.
12.
13.
0.257,
0.2EB
4,5
dB
0.250
4,lO
dB
0.57 0.70
0.2EE
4,15
dB
0.32 0.39
Key in 0.2E7 SPCL and 50.6 SPCL. Increase the signal source frequency until the display drops
to 1.0. Record the signal source’s frequency.
Decrease the signal source frequency until the display rises
to
2.0 then drops
to
1.0. Note the signal
source’s frequency. The difference between this frequency and the frequency in step 7 should be
between 33 and
55
kHz.
If
faulty, see Service Sheet 7 and check the Second Channel
1
Filter.
Key in 0.25F SPCL
to
select channel 2. Key in
50.6
SPCL. Set the signal source frequency to
455
kHz then fine tune the source to peak the signal on the Modulation Analyzer’s display. (Filter
passband ripple can be as high
as
2
dB.
Find the highest peak
of
the ripple.) The display should
read between
1.5
and 2.5. If faulty, see Service Sheet 7 and check Second Channel
2
Filter.
Set the signal source level for a Modulation Analyzer display of 2.00.
Increase the signal source frequency until the display
drops
to
1.0.
Record the signal source’s
frequency.
Decrease the signal source frequency until the display rises
to
2.0 then drops to 1.0. Note the signal
source’s frequency. The difference between
this
frequency and the frequency in step
11
should be
between
3
and
7
kHz. If faulty, see Service Sheet
7
and check the Second Channel 2 Filter.
Key in 0.2FO SPCL to read back the Option
Series
030 Installed Indicator. The Modulation
Analyzer should display
000001.0000.
If
faulty, see Service Sheet
7
and check the Option Series
030 Installed Indicator.
(J8)
IF
Amplifier/Detector Check (Option Series
030)
(2642A
and Above)
1.
2.
3.
4.
5.
6.
Set the signal generator
or
audio synthesizer to between 454 and 456 kHz CW at -70
dBm
(70.7
,uVrms into
50R).
Connect its
RF
output to A71J2
(IF
IN) on the Measuring Receiver.
Connect a high-impedance, ac coupled oscilloscope to A71J1
(TEST
JACK).
Press the blue key, then press INSTR PRESET (the AUTOMATIC OPERATION key) to preset
the instrument. Key in 0.397 SPCL and 0.3E7 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
dE3.
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 34 and check the circuits of channel
1.
Key in 49.C SPCL to read the
IF
with the
IF
RMS Detector. Calculate
reading of step
3
x
1.63.
The Measuring Receiver’s display should read within
10%
of the calculated value.
If
faulty, see
Service Sheet 34 and check the
IF
RMS Detector.
Set the signal source level for a Measuring Receiver display of
2.00.
Key in the Direct Control Special Functions listed in Table 8-13 followed each time by 49.C
SPCL.
For
each setting, the Measuring Receiver’s display should be as indicated.
If
faulty, see
Service Sheet 34 and check the corresponding attenuator.
Service Sheet
BD3
8D-35
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