Dell Precision 490 - Manual (Page 138)

9. Disconnect the front fan from the connector labeled FAN_FRONT on the system board. (See System Board Components .)
10. If the system is in tower mode, pull to remove the full-length card retainer piece beside the card fan.
11. Disconnect the Power1 and Power2 connectors from the system board (see System Board Components ).
12. Remove the cables from the cable guide on the front fan.
13. Press the tab between the card fan and the front fan towards the card fan as you lift it up and out of the computer.
14. Unscrew the fan case and lift to remove it from the computer.
15. Remove any components that restrict access to the system board.
16. Disconnect all cables from the system board.
17. Before you remove the existing system board, visually compare the replacement system board to the existing system board to make sure that you have
the correct part.
18. Remove the 9 system board screws.
19. Lift the system board from the computer.
20. Place the system board that you just removed next to the replacement system board.
1 card fan
2 card fan cable
3 card fan system-board connector (FAN_CCAG)
4 front fan
5 full-length card retainer piece
1 screws (9)
2 system board