Advertisement
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 a t -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
Advertisement
