Lenovo ThinkCentre M55 - Manual (Page 28)

9. Holding the microprocessor with your fingers, remove the protective cover
2 that protects the gold contacts on the new microprocessor 1 .
10. Position the microprocessor so that the notches on the microprocessor are
aligned with the tabs in the microprocessor socket.
Important
To avoid damaging the microprocessor contacts, do not tilt the
microprocessor when installing it into the socket.
11. Lower the microprocessor straight down into the microprocessor socket.
Note: Install the black protective cover that was removed from the new
microprocessor onto the defective microprocessor after the installation is
complete.
20 Hardware Replacement Guide