IBM 6150 Hardware Maintenance Manual page 182

Step 22
TNL SN32-9004 (August 87) to 75X0152 or 75X0166
The following FRUs are the most likely to cause a failure in the fixed-
disk and diskette drives.
Exchange the FRUs that have not been exchanged in the following order.
Test each FRU by running System Checkout. If you identify a failing
FRU, use the removal and replacement procedures in the section that
applies to the FRU and exchange it, then go to "Step 25" on page
3-0060-26. If you cannot identify a failing FRU, contact your service
support person.
1. An adapters for the fixed-disk and diskette drives.
2. The cables for the fixed-disk and diskette drive.
3. The IBM AT High Capacity Diskette Drive.
4. The system board.
5. The processor board.
6. The power supply.
7. The display adapter.
8. A memory expansion option in slot C.
9. The cooling fan.
10. The display.
11. The keyboard.
(8/87) Problem Isolation Charts 3-0060-23