Dell DR4000 Owner's Manual page 110

5 Disconnect the power cable from the end of the SAS backplane.
6 Disconnect the SAS data cables from the backplane.
7 Disconnect the USB cable and the control-panel cable.
CAUTION:
8 Disconnect the internal hard-drive cables.
9 While pressing the two blue latches toward each other, lift the backplane
upward. See Figure 3-24.
10 When the backplane cannot slide upward any further, pull the backplane
toward the back of the system to remove it from the retention hooks.
11 Lift the board out of the system, being careful to avoid damaging
components on the face of the board.
12 Place the SAS backplane face down on a work surface.
110
Installing System Components
Handle the cables gently to prevent damage.