170 N9030B PXA Signal Analyzer Service Guide
RF Section Troubleshooting (RF/Microwave Analyzers)
Troubleshooting
the analyzer LO phase lock loop to unlock, which would affect the LO
frequency measurement. The LO signal should measure 5122.5 MHz at
+10 dBm ± 3 dB.
If the signal level is incorrect, measure the signal coming from the A20 YTO at
A13A1J4. In order to measure this signal and avoid an LO Unlock, you will need
to install a power splitter at A13A1J4. Connect one arm of the splitter to
A13A1J4 using a sma (m) to sma (m) adapter. Connect the input of the splitter
to W20 using the sma 90 degree adapter and short sma cable. Connect the
measuring spectrum analyzer to the other arm of the splitter. Add the loss
through the splitter arm which is 6 dB for the Keysight 11667B splitter. The
signal should be 5122.5 MHz at +10 dBm ± 3 dB.
When measuring A13A1J5, Synth Out, the splitter must also be used. The
expected signal level is 5122.5 MHz at +10 dBm ± 3 dB
A13 Front End Assembly Verification
Many portions of the Front End Assembly have been verified earlier in the High
Band troubleshooting process outlined above.
The input signal level was measured on W15 as part of the A13 Front End Input
Verification.
The output signal level was measured at A13A1J7 during the quick check to
verify the High Band signal path.
The LO input at W20, and the LO outputs were tested when performing the
First LO Verification.
High Band Preamp (Option P08, P13, P26)
If a preamp option listed above is installed, the High Band preamp can be
verified as follows:
View the 4.8 GHz calibrator signal on screen. Press AMPTD, More, Internal
Preamp, Full Range to activate the preamp.The expected operation is the
signal level will not change more than +/- 0.5 dB and the noise floor will
increase due to the fact the input attenuation was automatically increased.
If the amplitude error when switching the preamp on and off is greater than 0.5
dB, assure that any other internal alignment failures are resolved since the
System Gain alignment must run before optimum performance is possible. The
amplitude error could be caused by poor frequency response, and performing
the high band frequency response adjustment (using the calibration software)
will adjust the preamp on, high band path. Assure you have evaluated all
causes including A15 Front End Controller switching problems, before you
replace the Front End assembly.
The A13 Front End assembly is shown as A13A1 and A13A2 for
troubleshooting clarification. However, A13A1 and A13A2 are not
separately replaceable. The entire A13 assembly must be replaced.
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