IBM Power System 9040-MR9 Manual page 18

DANGER: Multiple power cords. The product might be equipped with multiple AC power cords
or multiple DC power cables. To remove all hazardous voltages, disconnect all power cords
and power cables. (L003)
7. Remove the power supplies enough to prevent them from interfering with the removal of the system
backplane.
a) To unseat the power supply from its position in the system, push in the locking-tab (A).
b) Using the handle (B), pull the power supply (C) approximately 2.5 cm (1 in) away from the system.
c) Repeat steps "7.a" on page 4 through "7.b" on page 4 to remove the remaining power supplies.
Figure 2. Partially removing the power supplies
4 Power Systems: System backplane