E8257D/67D, E8663D PSG Signal Generators Service Guide
Troubleshooting
Troubleshooting the RF Path
1-77
Troubleshooting Pulse Modulation
1. Verify a license key has been entered for either Option UNU or UNW.
2. Run a full self–test and troubleshoot any reported failures before proceeding.
3. Determine the frequency of the pulse modulation problem.
4. Configure the signal generator to the pulse modulation setting that produces the problem.
5. Connect an oscilloscope to the LF OUTPUT connector. The waveform should be present on the oscilloscope.
6. If the waveform is present, continue to step 7.
7. If the waveform is not present or the signal is not the correct amplitude or type, replace the A11 Pulse/Analog
Modulation Generator.
8. Turn ALC Off. In ALC On mode, the ALC bandwidth limits pulse amplitudes at pulse widths <1μs. If turning ALC
Off corrects the problem, then verify that pulse modulation is setup in either ALC Off or Power Search Modes.
Troubleshooting Problems <3.2 GHz
9. If the pulse modulation problem occurs at <3.2 GHz, check P52–23 on the A31 Motherboard. Compare the results
with Table 1- 24.
10. If signal levels are good, replace the A8 Output.
11. If the signals are bad, check the cable continuity. If the cable is bad, replace the cable. If the cable is good replace
the A11 Pulse/Analog Modulation Generator.
Troubleshooting Problems >3.2 GHz
12. If the pulse modulation problem occurs >3.2 GHz, remove the cable A30 Modulation Filter J7 (W17). Probe the end
of the cable. Compare the results with Table 1- 25.
13. If the signal levels are good, replace the A30 Modulation Filter.
14. If the signal levels are bad, check the cable continuity. If the cable is bad, replace the cable. If the cable is good
replace the A11 Pulse/Analog Modulation Generator.
Troubleshooting AT1 Attenuator
The attenuator in a E8267D signal generator steps (changes levels) every 5 dBM. In a E8257D Option 520/532/540
signal generator the attenuator steps 5 dBM for the first change, then ever 10 dBM. In a E8257D 550/67 signal
generator the attenuator steps every 10 dBM.
1. If the attenuator switches at the switch points but the power does not change or the power changes more or less
than expected, replace the attenuator.
2. If the attenuator does not switch, press:
Utility > more 1 of 2 > Instrument Info > Options Info
An Option 1E1 should be listed.
3. If Option 1E1 is not listed, the option is either not installed or the configuration file is bad. The signal generator
will need to be returned to Agilent for service.
4. If Option 1E1 is listed, turn the signal generator off and remove W36 from J13 on the A26 MID.
5. Turn the signal generator on and probe the following pins on J13.
Table 1-24
Pulse On Pulse Off
+5 Vdc 0 to +5 Vdc (pulses at modulation rate)
Table 1-25
Pulse On Pulse Off
+5 Vdc 0 to +5 Vdc (pulses at modulation
rate)
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