Dell OptiPlex 990 (Early 2011) - Manual (Page 48)

9. Remove the control panel board.
Installing The Control Panel
1. Insert the control panel board into the slot on the chassis front.
2. Tighten the screw to secure the control panel board.
3. Thread the control panel-speaker cable into the chassis clip.
4. Connect the control panel cable to the system board.
5. Install the memory .
6. Install the drive cage .
7. Install the front bezel .
8. Install the cover .
9. Follow the procedures in After Working Inside Your Computer .
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