Dell OptiPlex 3000 Tower Service Manual page 58

Steps
1. Slide the power-supply unit into the chassis until the securing tab snaps into position.
2. Replace the three (#6-32) screws to secure the power-supply unit to the chassis.
3. Route the power cable through the routing guides on the chassis and connect the power cables to their respective
connectors on the system board.
58 Removing and installing components