Installation guide

Troubleshooting
Troubleshooting Unlocks
1-69
512 Reference Unlocked
A 512 Reference Unlocked message indicates a problem with the 10 MHz reference phase-lock loop
on the A18 Reference.
❏ Check for and disconnect any external reference signals that are connected to the instrument.
— If the unlock message goes away when the external reference signal has been disconnected, check that
the external reference signal meets the specifications for an external reference.
— If the unlock message is present with the external reference disconnected, replace the A18 Reference.
(Refer to “A18 Reference” on page 2-42.)
513 1 GHz Out of Lock
A 513 1GHz Out of Lock message indicates a problem with the 1 GHz phase-lock loop on the A18 Reference.
❏ Check for and disconnect any external reference signals that are connected to the instrument.
— If the unlock message goes away when the external reference signal has been disconnected, check that
the external reference signal meets the specifications for an external reference.
— If the unlock message is present with the external reference disconnected, replace the A18 Reference.
(Refer to “A18 Reference” on page 2-42.)
508 Frac-N Loop Unlock (Option 501, 502, 503, 504)
A 508 Frac-N Loop Unlock message indicates a problem with the Voltage Control Oscillator's (VCO)
phase-lock loop on the A17 Synthesizer (Option 501, 502, 503, 504).
❏ Check the 10 MHz signal on the A23 Motherboard at J10 pin 99 using an oscilloscope.
The signal should have a period of 100 ns and an amplitude of greater than 1.2 Vp-p.
— If the signal is good, replace the A17 Synthesizer (Option 501, 502, 503, 504).
(Refer to “A17 Synthesizer (Option 501, 502, 503, 504)” on page 2-40.)
— If the signal is bad, troubleshoot the A18 Reference.
(Refer to “Self-Tests 8xx for the A18 Reference” on page 1-50.)
508 Frac-N Loop Unlock (Option UNJ and Option 506)
A 508 Frac-N Loop Unlock message indicates a problem with the Voltage Control Oscillator's (VCO)
phase-lock loop on the A16 Frac-N (Option UNJ or Option 506).
❏ Check the 10 MHz signal on the A23 Motherboard at J10 pin 99 using an oscilloscope.
The signal should have a period of 100 ns and an amplitude of greater than 1.2 Vp-p.
— If the signal is good, replace the A16 Frac-N (Option UNJ or Option 506).
(Refer to “A16 Frac-N (Option UNJ or Option 506)” on page 2-38.)
— If the signal is bad, troubleshoot the A18 Reference.
(Refer to “Self-Tests 8xx for the A18 Reference” on page 1-50.)