Dell Precision T3400 (Late 2007) - Manual (Page 256)

256
Adding and Replacing Parts
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.
Removing the Power Supply
1 Follow the procedures in "Before You Begin" on page 143.
2 Remove the computer cover (see "Removing the Computer Cover" on
page 145).
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.