Dell Precision 3660 Tower Service Manual page 77

Steps
1. Remove the (#6-32) screw that secures the front I/O-bracket to the chassis.
2. Slide and remove the front I/O-bracket from the chassis.
3. Disconnect the power and HDD cables that are connected to the system board and unroute them from the routing guides on
the chassis.
4. Remove the nine (#6-32) screws that secure the system board to the chassis.
5. Lift the system board at an angle and remove the system board off the chassis.
Removing and installing components 77