Keysight Technologies X Series Service Manual page 132

Troubleshooting
Unlocked Issues
phase lock loops to be unlocked. In this case both the reference and the
synthesizer unlock error messages would be present. So before
troubleshooting a synthesizer unlocked condition make sure that there is no
reference unlock error. If there is, resolve the reference unlock condition first.
For the CXG and EXG series instruments there are two possible synthesizer
unlock errors:
— 508 Synthesizer Unlocked; Sum Loop (over). The synthesizer is unlocked.
— 508 Synthesizer Unlocked; Sum Loop (under). The synthesizer is unlocked.
For the MXG series instruments there are five possible synthesizer unlock
errors:
— 508 Synthesizer Unlocked; FracN Loop. The synthesizer is unlocked.
— 508 Synthesizer Unlocked; Offset Loop (over). The synthesizer is unlocked.
— 508 Synthesizer Unlocked; Offset Loop (under). The synthesizer is unlocked.
— 508 Synthesizer Unlocked; Sum Loop (over). The synthesizer is unlocked.
— 508 Synthesizer Unlocked; Sum Loop (under). The synthesizer is unlocked.
As can be seen from the unlock errors listed, the phase lock loop that is
unlocked is clearly identified in each of the error messages. There are also
adjustments for each of the phase lock loops in the performance verification
and adjustment software.
Use the following procedure to troubleshoot a 508 Synthesizer Unlocked error:
1. Verify that there is no 512 Reference Unlocked or 515 Reference Missing
2. From the 508 Synthesizer Unlocked error message given, determine which
3. Referring to
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Service may be needed.
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errors. If there are, resolve those issues first.
synthesizer phase lock loop is unlocked (FracN Loop, Offset Loop, or Sum
Loop).
Table 6-1, run the applicable synthesizer adjustments for the
phase lock loop that is unlocked.
Keysight CXG, EXG, and MXG X-Series Signal Generators Service Guide