HP 7925D Service Manual page 93

7925
Replace PCA-A4. If malfunction remains,
check for inactive UWG signal at A4P2·9.
Replace PCA·A6. If malfunction remains,
check current paths from A4Pl-H to A6Pl·E
and from A3P2·S to A4P2-S for open circuit.
Troubleshooting
NOTES:
1. Refer to the following diagrams for circuit details.
• Read/Write System Functional Diagram, fig. 4-28.
• Sector Sensing System Functional Diagram, fig. 4-27.
• F:ault Detection System Functional Diagram, fig. 4-29.
2. PCA's associated with DC.
W
malfunction include:
• I/O sector PCA-A2/microprocessor.
• Drive control PCA-A4.
• Track follower PCA-AS.
• Read/Write PCA·A6.
Replace PCA-A2. If malfunction remains,
check current path from A2P2·9 to A4P2-9
for open circuit. If none, check for SCL pulse
train at ASP2-6.
Replace PCA-AS. If malfunction remains,
'------... check current path from ASP2·6 to A2P2·6
for short to ground.
Check current path from ASP2-6 to A2P2·6
for open circuit.
7311-11 B
Figure 4-9. DC. W LED Indicator Troubleshooting Flowchart
4-19