130 Keysight CXG, EXG, and MXG X-Series Signal Generators Service Guide
Troubleshooting
Unlocked Issues
Unlocked Issues
There are two basic types of phase detector unlock errors that the instrument
could have; reference unlock and synthesizer unlock. The reference unlock
error number is 512 while the synthesizer unlocks are 508. There is only one
512 reference unlock error and 5 possible 508 synthesizer unlock errors.
512 Reference unlocked; There is a problem with the external reference
settings or connections. If reference is internal check Ref Oscillator Tune.
508 Synthesizer Unlocked; FracN Loop. The synthesizer is unlocked.
Service may be needed.
508 Synthesizer Unlocked; Offset Loop (over). The synthesizer is unlocked.
Service may be needed.
508 Synthesizer Unlocked; Offset Loop (under). The synthesizer is unlocked.
Service may be needed.
508 Synthesizer Unlocked; Sum Loop (over). The synthesizer is unlocked.
Service may be needed.
508 Synthesizer Unlocked; Sum Loop (under). The synthesizer is unlocked.
Service may be needed.
For more information on the Unlock error messages refer to the
X-Series Signal Generators Error Messages Guide using the following link:
http://literature.cdn.keysight.com/litweb/pdf/N5180-90075.pdf.
512 Reference Unlocked
This unlock indicates that the phase lock loop for the 100 MHz VCXO in the
reference section of the A3 RF assembly is unlocked. The 100 MHz VCXO is
supposed to be phase locked to either the instrument internal 10 MHz
reference or an external reference input on the rear panel.
If the instrument has option 1ER the external reference frequency can be 1
MHz to 50 MHz as long as the Ref Oscillator Ext Freq setting under the Freq,
Reference Oscillator menu is set to match it.
The instrument has three different settings for the selection of the Reference
Oscillator Source. They are Internal, External, and Auto. The default setting is
Auto. When set to Auto the instrument will use the internal reference oscillator
if no external reference is present but will automatically switch to an external
reference once one is detected. If the reference oscillator source is set to
external and the signal goes away an error will be displayed, and the RF output
of the source will be turned off.
If the reference phase lock loop is unlocked the RF output of the signal
generator will typically still be active, there will just be a larger than usual
frequency error.
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