Dell Precision R5400 (Mid 2008) - Manual (Page 29)

4. Disengage the power supply and slide it partway out of the power supply bay (see Removing the Power Supply ).
5. Remove both expansion-card cages (see Removing an Expansion-Card Cage ), ensuring that you disconnect the power cable connectors labeled "P5"
and "P6" from any expansion cards installed in the card cages.
6. Remove the mid-support brace (see Removing the Mid-Support Brace ).
7. Remove the cooling shroud (see Removing the Cooling Shroud ).
8. Disconnect the power cable connectors labeled "P1," "P2," "P3," and "P4" from the system board.
9. Unscrew the three captive screws on the power distribution unit that secure it to the bottom of the chassis.
10. Disengage the power cables from the cable clips, cable-routing channels, and cable-routing portals on the chassis as you lift the power distribution unit
out of the chassis, easing the power cables along behind it.
Replacing the Power Distribution Unit
1. Lower the power distribution unit onto the screw mounts on the bottom of the chassis, and tighten the three captive screws.
2. Reconnect the hard-drive power cable(s) to power-cable connector P8 (hard drive in upper bay) and connector P7 (hard drive in lower bay, if applicable).
3. Reconnect the optical-drive power-cable connector P9 to the back of the optical drive.
4. Tuck connectors P7 and P8 and their cables down into the space between the power distribution unit and the back of the hard drives.
connector (P8) connector (P9)
11 optical-drive SATA data cable 12 cable-routing clip (power cables
P4, P5, and P6)
13 cable-routing channel (power
cables P4, P5, and P6)
14 cable-routing clip (power cables
P4, P5, and P6)
15 power-cable connector P4 16 storage for power cables P5 and
P6 (when not in use)
NOTE: If power cables P5 and P6 are not connected to any expansion card, ensure that you disengage them from their storage shelf in the side
wall of the chassis.
NOTE: Each portal has an arm that hinges up and down over the opening.
1 power cables 2 captive screws (3)
3 power distribution unit 4 cable-routing portals (2)
CAUTION: Only trained service technicians are authorized to remove the computer cover and access any of the components inside the computer.
Before working inside the computer, read the safety information that shipped with the computer. For additional safety best practices information,
see the Regulatory Compliance Homepage at www.dell.com/regulatory_compliance.