Dell OptiPlex 755 - Manual (Page 235)

If you are installing a processor replacement kit from Dell, return the processor to Dell in the same package in which your replacement kit was sent.
12. Clean the thermal grease from the bottom of the heat sink.
13. Apply the new thermal grease to the top of the processor.
14. Place one end of the heat sink under the tab on the retention base on the side opposite the release lever.
15. Lower the heat sink onto the processor at a 45-degree angle so that one end of the heat sink fits securely under the tab opposite the release tab on
the retention base.
16. Re-assemble the shroud.
17. Replace the computer cover (see Replacing the Computer Cover ).
18. Replace the cable cover, if used (see Cable Cover (Optional) ).
1 processor cover 6 release lever
2 tab 7 front alignment-notch
3 processor 8 socket and processor pin-1 indicator
4 processor socket 9 rear alignment-notch
5 center cover latch
NOTICE: Ground yourself by touching an unpainted metal surface on the back of the computer.
NOTICE: Ensure that you apply new thermal grease. New thermal grease is critical for ensuring adequate thermal bonding, which is a requirement for
optimal processor operation.
1 heat sink
2 retention base
3 release lever