HP 7925D Service Manual page 91

7925 Troubleshooting
NOTE:
Refer to the following diagram for circuit details.
• Read/Write System Functional Diagram, fig. 4·28.
No
Use diagnostic operator design program to
verify that W.
AJ:5
occurs when individually
formatting each head.
Replace defective head.( Refer to para. 5-18.)1-------------------~
Verify that data cable is connected at both
ends and is continuous.
Reconnect or replace data cable.
Replace PCA-AG. If fault remains, replace
PCA-A4. If fault remains, replace PCA-A7.
Using diagnostic operator design program,
tell drive to read full sector and loop. Scope
A4TP RDA and TP ROB. Check for pres-
ence of data bursts, separated by 100 Jisec
of intersector gap. If M version drive, remove
data cable from 13037 Disc Controller and
scope wire terminations.
No
Replace device controller PCA 13037-60028
in 13037 Disc Controller or data PCA·A 1.
Trace signals to locate open circuit and
repair.
7311-98
Figure 4-7. W. AC LED Indicator Troubleshooting Flowchart
4-17