Dell Precision 390 - Manual (Page 103)

14. Remove the mounting screw from the I/O panel.
15. Remove the I/O panel from the computer.
Replacing the I/O Panel
Follow the removal procedure in reverse order, ensuring that the tabs on the top panel, bottom panel, and front panel are secure.
Power Supply
Removing the Power Supply
1. Follow the procedures in Before You Begin .
2. Remove the computer cover (see Removing the Computer Cover ).
3. Disconnect the DC power cables from the system board and the drives.
Note the routing of the DC power cables underneath the tabs in the computer frame as you release the tabs and remove the cables from the system
board and drives. You must route these cables properly when you replace them to prevent their being pinched or crimped.
4. Remove the four screws that attach the power supply to the back of the computer chassis.
1 I/O panel 2 mounting screw
CAUTION: Before performing any of the procedures in this section, follow the safety instructions in the Product Information Guide.
CAUTION: To guard against electrical shock, always unplug your computer from the electrical outlet before opening the cover.
NOTICE: To prevent static damage to components inside your computer, discharge static electricity from your body before you touch any of your
computer's electronic components. You can do so by touching an unpainted metal surface on the computer.