HP 8560A Service Manual page 371

8. If the YTO Frequency Error recorded in step 5 is less than 10 MHz, do the following:
a. Measure the frequency at A14J304. The frequency should be equal to the frequency
recorded in step 6. If not, refer to "Unlocked Roller Oscillator PLL" in this chapter.
b. Measure the input and output levels of the A15A2 Sampler. If the sampler appears
defective, check the LO drive to the sampler as described in "Sampler and Sampler
IF."
c. Refer to steps 35 through 49 below.
9. If the YTO Frequency Error recorded in step 5 is between 10 and 30 MHz, do the
following:
a. Find the Main Roller Frequency in Table lo-12 that matches the frequency recorded in
step 6. Locate the corresponding acceptable YTO Frequency Error range in the table.
Note Table lo-12 shows how close in frequency the YTO must be in order to
phase-lock when the loop is closed. The range is a function of where the
main roller oscillator is tuned. The Main Roller Frequency column (showing
polarity) indicates whether the YTO frequency is above (-t) or below (-) the
sampler's harmonic.
b. If the YTO Frequency Error recorded in step 5 is outside the range listed in Table
10-12, perform the following steps.
i. Check the YTO Adjustments using the TAM.
ii. Check the YTO DACs using the procedure in steps 41 through 49 below or using
Manual Probe Troubleshooting with the TAM on A14J17 and A14J18.
iii. Refer to steps 10 through 34 below.
c. If the YTO Frequency Error recorded in step 5 is within the range listed in
Table 10-12.
i. Measure the frequency at A145304. The frequency should be equal to the frequency
recorded in step 6. If not, refer to "Unlocked Roller Oscillator PLL" in this
chapter.
ii. Measure the input and output levels of the A15A2 Sampler. If the sampler appears
defective, check the LO drive to the sampler as described in "Sampler and Sampler
IF" in this chapter.
iii. Refer to steps 35 through 49 below.
Synthesizer Section lo-27