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Service
Model 8901B
(J7) Channel Filter Check (Option Series 030)
(2374A to 2636A)
1.
Set the signal generator or audio synthesizer to between 454 and 456 kHz CW at -10 dBm (70.7
2.
Connect a high-impedance, ac coupled oscilloscope to A55J1
(IF OUT).
3. Press the blue key, then press INSTR PRESET (the AUTOMATIC OPERATION key) to preset
the instrument. Key in 0.2DO SPCL to switch in the Channel Output Attenuator and select
channel
1.
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 640 and 1000 mVpp. If faulty, see Service Sheet
33 and check the circuits of channel
1.
4. Set the oscilloscope gain for a display of 6 divisions peak-to-peak. Key in 0.2D1 SPCL to switch
out the Channel Output Attenuator. Decrease the oscilloscope's vertical gain by a factor of 10.
The waveform should be between 5.9 and 6.1 divisions peak-to-peak. If faulty, see Service Sheet
6 and check the Channel Output Attenuator.
5. Increase the signal source frequency until the waveform drops to 3 divisions peak-to-peak. Record
the signal source's frequency.
6. 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 5 should be as indicated in Table 8D-9. (The filter bandwidth
depends on the option installed.) If faulty, see Service Sheet 6 and check the First Channel 1 Filter.
mVrms into 50R). Connect its RF output to A5552 (IF IN) on the Modulation Analyzer.
lbble
80-9.
Bandwidth of First Channel
1
Filter, @) Step 6
Ice
Limits (kHz)
1
Option Combination
033 and 035
035 and 037
032 and 033
033 and 037
12.4
032and037
I
6.4
Maximum
10.4
7. Key in 0.2D3 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 6 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-10. If faulty, see Service
Sheet 6 and check the First Channel 2 Filter.
8D-32
Service Sheet BD3
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