Installation guide

Troubleshooting
Troubleshooting Unlocks
1-71
521 YO Loop Unlocked (Option UNJ and Option 506)
A 521 YO Loop Unlocked message indicates a problem with the YO phase detector
on the A15 Sampler (Option UNJ or Option 506).
1. Turn power on to the signal generator.
2. Remove the A15 Sampler (Option UNJ or Option 506).
3. Set the signal generator to 525 MHz.
4. Using a signal analyzer, check for the presence of signals as shown in Table 1-32:
• If all signals are good, replace the A15 Sampler (Option UNJ or Option 506).
(Refer to “A15 Sampler (Option UNJ or Option 506)” on page 2-36.)
• If any signal is bad, troubleshoot one of the following two assemblies:
— either the A21 YTO Driver (Option UNJ or Option 506)
(Refer to “Self-Tests 6xx for the A21 YTO Driver (Option UNJ or Option 506)” on page 1-42.)
— or the A16 Frac-N (Option UNJ or Option 506)
(Refer to “Self-Tests 7xx for the A16 Frac-N (Option UNJ or Option 506)” on page 1-45.)
516 Baseband Generator Unlock
A 516 Baseband Generator Unlock message indicates a problem with the Voltage Control Oscillator's (VCO)
phase-lock loop on the A7 Baseband Generator (Option 001 or Option 002).
❏ Check the 10 MHz signal on the A23 Motherboard at J1 pins 26 and 91 using an oscilloscope.
The signal period should be 100 ns with an amplitude of approximately 1.0 Vp-p or greater.
— If the 10MHz signal is good, replace the A7 Baseband Generator (Option 001 or Option 002).
(Refer to “A7 Baseband Generator (Option 001 or Option 002)” on page 2-22.)
— If the signal is not present, troubleshoot one of the following two assemblies:
— either the A23 Motherboard
(Refer to “Self-Tests 21xx for the A23 Motherboard” on page 1-66.)
— or the A18 Reference
(Refer to “Self-Tests 8xx for the A18 Reference” on page 1-50.)
Table 1-32
Signal Generator Output
(MHz)
Output of A21 YTO Driver
(Option UNJ or Option 506)
Sampler End of W37
Output of A15 Sampler
(Option UNJ or Option 506)
Sampler End of W11
Tune A15J3
( >
−20 dBm, ±10 MHz )
A15J6
( > +5 dBm, ±10 MHz )
525 4200 796.875
750 6000 644.53
500 8000 593.75