Dell Precision T7400 (Late 2007) - Manual (Page 167)

Adding and Replacing Parts 167
DC Power Connector FDD
Removing the Power Supply
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.
1 Follow the procedures in "Before You Begin" on page 139.
2 Remove the computer cover. See "Removing the Computer Cover" on
page 141.
3 Disconnect the DC power cables from the system board, the drives, and
any other cards or devices to which they are connected.
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.
Pin Number Signal name 18-AWG Wire
1 5 V Red
2 COM Black
3 COM Black
4 12 VC Blue/White