Dell OptiPlex 990 (Early 2011) - Manual (Page 42)

Installing The System Board
1. Align the system board to the port connectors on the rear of the chassis,
and place the system board in the chassis.
2. Tighten the 7–mm hex screw to secure the system board to the chassis.
3. Tighten the screws to secure the system board to the chassis.
4. Thread the internal antenna into the chassis clips.
5. Connect the SATA cables, hard/optical drive power cable, system fan cable
and the control panel cable to the system board.
6. Install the internal speaker .
7. Install the wireless module .
8. Install the front Input/Output panel .
9. Install the memory .
10. Install the heat sink .
11. Install the power supply .
12. Install the drive cage .
13. Install the front bezel .
14. Install the cover .
15. Follow the procedures in After Working Inside Your Computer .
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