Keysight N9038A MXE Service Guide 391
Optional Assemblies
A25 Wideband Analog IF Assembly Troubleshooting
Input Switching Verification
The input of the A25 Wideband Analog IF assembly is designed such that the
input signal presented to it at J101 can be either used by this assembly itself or
routed back out of J102 to be used by the A3 Digital IF 40 MHz IF path.
However, since the N9038A MXE EMI Receiver does not have an option for a
40 MHz analysis bandwidth there is no time other than during internal
alignments that this signal path is used. So there is no way to manually verify
that this switching is working properly.
If there is a problem with the input signal switching back out though J102 to
the A3 Digital IF assembly the internal alignments will have failures for
everything related to either the DIF40 or MediumBandIF.
While the exact levels cannot be verified, the existence of a signal coming out
of J101 during an instrument internal alignment can be verified by following
this procedure:
1. Referring to Figure 14-1, disconnect coaxial cable W15 from A25 J102
2. Connect a cable from J102 to the input of a spectrum analyzer to verify
the presence of a signal
3. Tune the spectrum analyzer to 250 MHz with a span of 1 MHz
4. Set the spectrum analyzer to use Video Trigger with a Trigger Level of
-60.0 dBm
5. Set the spectrum analyzer to Single trigger so that it will capture only one
signal
6. Run the instrument internal alignment by pressing System, Alignments,
Align Now, RF Only
7. At some point during the alignment being run the spectrum analyzer
should trigger, with a signal that looks something like that seen in Figure
14-5.
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