192 Keysight N9038A MXE Service Guide
RF Preselector Section
RF Preselector Section Troubleshooting
Verifying Signal Through Path
1. Remove the instrument dress cover (MP24) and the top brace (MP10).
Refer to Chapter 16, “Service and Diagnostics Menus” for instructions on
removing these covers.
2. Referring to Figure 5-4, remove W31 and W36 from the A21 RF
Preselector Input assembly.
3. Turn the instrument on and allow it to complete its boot up process,
ignoring any error messages.
4. Turn the instrument self-alignment routine off by pressing System,
Alignments, Auto Align, Off.
5. Connect a signal generator to the A21 RF Preselector Input assembly RF
Input (J100), as shown in Figure 5-4.
6. Set the signal generator to an amplitude of −20 dBm.
7. Connect a spectrum analyzer to the A21 RF Preselector Input assembly RF
Output (J101), as shown in Figure 5-4.
8. Tune the spectrum analyzer to a start frequency of 0 Hz and a stop
frequency of 3.6 GHz.
9. Tune the A21 RF Preselector Input assembly to the through path by
entering the Service menu and pressing More, RF Preselector, Band Lock,
Through, Band 3.
10.Place one of the active traces on the spectrum analyzer into its Max Hold
function.
11.Slowly vary the frequency of the signal generator between 0 Hz and
3.6 GHz to verify the frequency response of the through path on the
spectrum analyzer display, as shown in Figure 5-19.
12.Verify that the signal level on the spectrum analyzer is between −25 dBm
and −30 dBm (±3 dB) across the frequency range, as shown in Figure 5-19,
allowing for any additional test cable loss.
If the signal level is incorrect the most likely cause of the problem is the
A21 RF Preselector Input assembly itself.
For information on how to access the instrument's Service menu see Chapter 16, “Service
and Diagnostics Menus.”.
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