Lenovo ThinkCentre A70 7099 Hardware Maintenance Manual page 118

CAUTION:
The heat sink and microprocessor might be very hot. Turn off the computer and
wait three to five minutes to let the computer cool before opening the computer
cover.
To replace the system board:
112
Hardware Maintenance Manual
1. Remove all media from the drives and turn off all attached devices and the
computer. Then, disconnect all power cords from electrical outlets and
disconnect all cables that are connected to the computer.
2. Remove the computer cover. See "Removing the computer cover" on page 88.
3. Remove the front bezel. See "Removing and reinstalling the front bezel" on
page 90.
4. Lay the computer on its side for easier access to the system board.
5. Disconnect the front audio and USB assembly cables from the system board.
See "Locating parts on the system board" on page 86.
6. Remove all memory modules and PCI cards that are currently installed. See
"Installing or replacing a memory module" on page 94 and "Installing or
replacing a PCI card" on page 91.
7. Carefully take note of the location of all cable connections on the system
board and disconnect all the cables. See "Locating parts on the system board"
on page 86.
8. Remove the heat sink and fan assembly from the failing system board. See
"Replacing the heat sink and fan assembly" on page 100.