Keysight N9038A, Service Manual

Page: 240 / 745

240 Keysight N9038A MXE Service Guide
RF Downconverter Section
RF Downconverter Section Troubleshooting
If the signal is:
— The correct level
Proceed to the next step
— Lower than expected
Switch the A11 RF Switch / High Band Preamp assembly
to the low band signal path by pressing FREQ , 50 MHz .
If the signal level decreases further, the most probable
cause is a bad A11 RF Switch / High Band Switch
assembly.
If the signal does not decrease any further, verify that the
switch control lines from the A15 Front End Control
assembly are working properly. Refer to Chapter 8, “Front
End Control.” for instructions on how to verify the control
lines.
21. Tune the signal generator and spectrum analyzer to any other frequency
above 3.6 GHz and verify that the loss through the high band signal path
remains within a few dB of the values outlined in Table 6-6 or Table 6-7 .
22. If the high band thru signal path loss continues to be within the expected
values, proceed to the High Band Preamp Path verification.
High Band Preamp Signal Path
23. Tune the signal generator to 6 GHz with an amplitude of -20 dBm.
24. Tune the spectrum analyzer to 6 GHz with a span of 1 MHz.
25. Switch the A11 RF Switch / High Band Preamp assembly to the high band
signal path by pressing FREQ , 6 GHz .
26. Verify that the signal amplitude on the spectrum analyzer display is
approximately what is expected, as outlined in Table 6-6 or Table 6-7 ,
allowing for any additional test cable loss, as seen in Figure 6-10 .
27. Set the spectrum analyzer marker at the peak of the signal and then turn
on its marker delta function.
28. Switch the A11 RF Switch / High Band Preamp assembly to the high band
preamp signal path by pressing AMPTD , More , Internal Preamp , Full
Range .
29. Verify that the signal amplitude increases by approximately what is
expected, as outlined in Table 6-6 or Table 6-7 , as shown in Figure 6-11 .