Dell OptiPlex 390 (Mid 2011) - Manual (Page 47)

Power Supply
16
Removing The Power Supply
1. Follow the procedures in Before Working Inside Your Computer .
2. Remove the cover .
3. Disconnect the power cables connected to the hard drive(s) and optical
drive(s).
4. Unthread the power cables from the clips in the computer.
5. Disconnect the 24-pin power cable from the system board.
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