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Model 8901B
Service
Direct Control
Special Function
0.250
a b l e
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 , l O
dB
0.57
0.70
0.2EE
4 , 1 5
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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