Dell OptiPlex 7020 (Mid 2014) - Manual (Page 26)

6. Push in on the blue release tab and slide the power supply towards the front of the computer.
7. Lift the power supply out of the computer
Installing the Power Supply
1. Place the power supply in the chassis and slide towards the back of the computer to secure it.
2. Tighten the screws securing the power supply to the back of the computer.
3. Connect the 4-pin and 8–pin power cables to the system board.
4. Thread the power cables into the chassis clips.
5. Install the:
a. drive cage
b. optical drive
c. front bezel
d. cover
6. Follow the procedures in After Working Inside Your Computer.
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