Dell OptiPlex 990 (Early 2011) - Manual (Page 51)

10. Lift the power supply out of the computer.
Installing The Power Supply
1. Place the power supply in the chassis and slide towards the back of the computer
to secure it.
2. Tighten the screws to secure the power supply from the back of the computer.
3. Thread the 24–pin power cable into the chassis clip.
4. Connect the 24–pin power cable to the system board.
5. Thread the 4–pin power cable into the chassis clips.
6. Connect the 4–pin power cable to the system board.
7. Install the PSU thermal sensor .
8. Install the cover .
9. Follow the procedures in After Working Inside Your Computer .
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