124 E8257D/67D, E8663D PSG Signal Generators Service Guide
Troubleshooting
Troubleshooting the RF Path
6. To measure the A6 Frac–N output level, with the signal generator on,
remove the A8 Output and probe the right hand mmx connector’s center
pin. The power level should be ≥+5 dBm.
7. If power levels look good through the path in ALC Off mode, the problem is
most likely in the ALC loop. Go to troubleshooting the ALC loop.
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 1-22.
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.
Always turn the signal generator off before installing any assembly.
Table 1-22
Pulse On Pulse Off
+5 Vdc 0 to +5 Vdc (pulses at modulation rate)
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