124 E8257D/67D, E8663D PSG Signal Generators Service GuideTroubleshootingTroubleshooting the RF Path6. 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 centerpin. The power level should be ≥+5 dBm.7. If power levels look good through the path in ALC Off mode, the problem ismost likely in the ALC loop. Go to troubleshooting the ALC loop.Troubleshooting Pulse Modulation1. Verify a license key has been entered for either Option UNU or UNW.2. Run a full self–test and troubleshoot any reported failures beforeproceeding.3. Determine the frequency of the pulse modulation problem.4. Configure the signal generator to the pulse modulation setting thatproduces the problem.5. Connect an oscilloscope to the LF OUTPUT connector. The waveformshould 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 ortype, replace the A11 Pulse/Analog Modulation Generator.8. Turn ALC Off. In ALC On mode, the ALC bandwidth limits pulse amplitudesat pulse widths <1μs. If turning ALC Off corrects the problem, then verifythat pulse modulation is setup in either ALC Off or Power Search Modes.Troubleshooting Problems <3.2 GHz9. If the pulse modulation problem occurs at <3.2 GHz, check P52–23 on theA31 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/AnalogModulation Generator.Always turn the signal generator off before installing any assembly.Table 1-22Pulse On Pulse Off+5 Vdc 0 to +5 Vdc (pulses at modulation rate)
