Troubleshooting Table
Table 1 correlates CRT
Table 1. Troubleshooting Using CRT Unlock Messages
Message | Probable Faulty Loop | Associated Assemblies | |||
(UNLOCK) |
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| |
PLl |
|
| Phase Lock Loop 1 | AlOAl to AlOA4 | |
PL2 |
|
| Phase Lock Loop 2 | AlOA5 to AlOA8 | |
REF |
|
| Reference | Loop | A7A1, A7A2, A22 |
YTO |
|
| YTO Loop | A19, A20, A21, All | |
M/N |
|
| M/N Loop | A7A3, A7A4 | |
HET |
|
| Heterodyne Loop | A6A9, A6A4 | |
PLl, | PL2 |
| Phase Lock Loop 2 | AlOA5 to AlOA8 | |
PLl, | YTO |
| Phase Lock Loop 1 | AlOAl to AlOA4 | |
PLl, | PL2, YTO | Phase Lock Loop 2 | AlOA5 to AlOA8 | ||
REF, PLl, | PL2 | Reference | Loop | A7A1, A7A2, A22 | |
REF, | M/N, | YTO | Reference | Loop | A7A1, A7A2, A22 |
M/N, YTO |
| M/N Loop |
| A7A3, A7A4 | |
HET, REF |
| Reference | Loop | A7A1, A7A2, A22 | |
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General
The simplified block diagram at the back of this chapter shows the assemblies involved in setting the start frequency. The HP 8566B has two tuning modes. For frequency spans greater than 5 MHz, a method called lock and roll is used. This basically involves phase locking the analyzer start frequency during the retrace period prior to the beginning of a new scan. For frequency spans of 5 MHz and less, the YTO Loop is
4 Analog Troubleshooting