HP 7925D Service Manual page 94

Troubleshooting
Replace peA-A5. If malfunction remains,
replace PCA-A3. If malfunction remains, reo
place PCA·A4.
No
Set RUN/STOP switch to STOP. Check for a
servo code signal at A5TP PRE when
RUN/STOP switch is set to RUN. NOTE:
Signal may be incoherent; however, the pre·
sence of a signal should be detectable while
heads are over cylinder area.
Check wiring from A5Pl·16 to A3Pl·16 and
from A3P2·S to A4P2·S for short to ground.
NOTES:
1. Refer to the following diagram for circuit details.
• Hnad Positioning System Functional Diagram,
fig. 4-26.
2. PCA's associated with AGC malfunction include:
• Servo PCA·A3.
• Drive control PCA-A4.
• Track follower PCA-A5.
Replace servo head.
(Refer to para. 5-l8.)
No
Replace pack.
7925
7311-12A
4-20
Figure 4-10. AGe LED Indicator Troubleshooting Flowchart