Lenovo ThinkCentre A55 Hardware Maintenance Manual page 142

10. Disconnect the heat sink and fan assembly cable from the system board. See
11. Remove the four screws 1 securing the heat sink and fan assembly to the
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Hardware Maintenance Manual
2. Place the computer on its right side to help make the system board more
accessible.
3. Remove any adapter cards installed in the PCI connectors.
4. Disconnect the signal and power cables from the hard disk drive.
5. Press the release tab 1 down, slide the hard drive cage 2 back, and pivot
the hard disk drive outward as shown.
6. Carefully take note of the location of all cable connections on the system
board and disconnect all cables. See the system board illustration for your
machine type at "Identifying parts on the system board" on page 130.
7. Remove the screws that secure the system board to the chassis.
8. Lift the system board out of the chassis.
9. Remove the memory modules from the failing system board and install them
in the same location on the new system board.
the system board illustration for your machine type at "Identifying parts on
the system board" on page 130.
system board.