Troubleshooting Information

Troubleshooting Table

Table 1 correlates CRT phase-lock error messages with the probable faulty phase-lock loop and associated assemblies. This is especially helpful in determining the faulty loop when more than one phase-lock error message is displayed.

Table 1. Troubleshooting Using CRT Unlock Messages

Message

Probable Faulty Loop

Associated Assemblies

(UNLOCK)

 

 

 

 

 

 

 

 

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

 

 

 

 

 

 

Start Frequency Tuning Equations and Phase Lock Troubleshooting

General

Phase-lock loop troubleshooting is much easier if it is understood how the start frequency is derived. The Diagnostic Functions of the spectrum analyzer can also be used to simplify troubleshooting of the phase-lock loop.

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 phase-locked during all of a sweep, and the stable 20/30 Loop PLL2 is swept.

4 Analog Troubleshooting