"The 1 GHz reference oscillator is unlocked. If an external reference is connected, check the frequency. If this error reoccurs when no external reference is connected, the instrument may require service."
If you get this error message without an external reference connected the unit requires servicing. This error occurs when the ABUS VTUNE node goes outside of its lock range of 2V - 4V, meaning it is probably a problem with the A11 Reference Assembly.
To correct this the reference assembly will probably need to be adjusted or replaced.
I looked this error up in the E44xx Error Guide:
Error 513 - 1 GHz Oscillator unlocked
"The 1 GHz reference oscillator is unlocked. If an external reference is
connected, check the frequency. If this error reoccurs when no external
reference is connected, the instrument may require service."
If you get this error message without an external reference connected the unit requires servicing. This error occurs when the ABUS VTUNE node goes outside of its lock range of 2V - 4V, meaning it is probably a problem with the A11 Reference Assembly.
To correct this the reference assembly will probably need to be adjusted or replaced.
Best regards,