IBM RT PC Options Installation page 66

TNL SN20-9864 (May 1987) to 75X0217
14. Put whichever drive adapter your system uses back in the appropriate
slot as shown below, and replace the screw.
Slot 1 (Fixed-Disk and Diskette
Drive Adapter)
15. If this is the last drive to be installed, replace the cooling fan
assembly. See "Cooling Fan Replacement" 'Qn page 2-7.
Section 2. Removing and Installing Drives in IBM 6150
2-28.1