Dell OptiPlex 790 (Early 2011) - Manual (Page 38)

9. Remove the screws that secure the power supply to the chassis.
10. Slide the power supply inward and remove the power supply.
Installing The Power Supply
1. Place the power supply in the chassis and slide it outward to secure it.
2. Tighten screws to secure the power supply to the chassis.
3. Connect the cables to the system board.
4. Install the
heat sink .
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