Dell Precision 330 - Manual (Page 61)

Installing Upgrades 61
Power Supply
To access some of the components on the system board, you may need to
rotate the system power supply out of the way.
CAUTION: Before you perform this procedure, see " Safety First—
For You and Your Computer ."
1 Turn off the computer and peripherals, disconnect them from their
electrical outlets, wait at least 5 seconds, and then remove the
computer cover .
2 Ensure that the AC power cable is disconnected from the AC power
receptacle on the back of the power supply. See " Rotating the Power
Supply (Mini Tower Chassis) " or " Rotating the Power Supply
(Desktop Chassis) ."
3 Free the power supply from the securing tab by pressing the tab
labeled "RELEASE." Then rotate the power supply upward until it
locks in its extended position.