IBM 6151 Maintenance And Service Manual page 172

Step 2
The diskette drive, fixed-disk drive and cooling fan have moving
parts and can cause noise problems.
CAN YOU IDENTIFY WHICH FRU IS CAUSING THE NOISE?
YES Do the following:
1.
Exchange the FRU.
2. Run the System Checkout.
3. This completes the repair.
NO
Continue on the next page.
3-0050-2 Service Manual