Installation guide

Troubleshooting
Troubleshooting Unlocks
1-70
520 Sampler Unlocked (Option UNJ and Option 506)
A 520 Sampler Unlocked message indicates a problem with the Voltage Control Oscillator’s (VCO) phase-lock
loop on the A15 Sampler (Option UNJ or Option 506).
❏ Run self-tests.
— If self-tests fail, troubleshoot the problem reported.
— If self-tests pass:
1. Turn power on to the signal generator.
2. Remove the A15 Sampler (Option UNJ or Option 506).
3. Connect a signal analyzer to the A15 Sampler (Option UNJ or Option 506) J1 input (W44 cable that
comes from the A18 Reference).
4. Check for the presence of a 1 GHz signal with a power level of 0 dBm or greater.
— If the signal is good on W44 cable connector for J1,
replace the A15 Sampler (Option UNJ or Option 506).
(Refer to “A15 Sampler (Option UNJ or Option 506)” on page 2-36.)
— If the signal is bad on the W44 cable connector for J1:
a. Turn power off to the signal generator.
b. Remove the A18 Reference.
(Refer to “A18 Reference” on page 2-42.)
c. Ohm the cable between the center pins (a short should be measured) and between the center
pin and shielding (an open should be measured) at J3 of the A18 Reference and J1
of the A15 Sampler (Option UNJ or Option 506).
— If the cable is good, troubleshoot the A18 Reference.
(Refer to “Self-Tests 8xx for the A18 Reference” on page 1-50.)
— If an open is measured between the center pins or a short between the center pins and the
shielding, replace the W44 cable.