Attention
Do not open your computer or attempt any repair before reading and understanding the "Important safety information" in the ThinkCentre Safety and Warranty Guide that came with your computer. To obtain a copy of the ThinkCentre Safety and Warranty Guide, go to the Lenovo Support Website.

This section provides instructions on how to replace the power supply assembly.

To replace the power supply assembly, do the following:

1. Turn off the computer and disconnect all power cords from electrical outlets.
2. Disconnect the power cords, Input/Output (I/O) cables, and any other cables that are connected to the computer.
3. Remove the four screws at the rear of the chassis that secure the power supply assembly.

4. Open the computer cover. See "Opening the computer cover".
5. Pivot the optical drive bay assembly upward to gain access to the power supply assembly.
6. Disconnect the power supply assembly cables from all drives and from the power connectors (1) and (2) on the system board.
   Note: You might need to remove the hard disk drive to gain easy access to the power connector (2). See "Replacing the hard disk drive".

7. Release the power supply assembly cables from the cable clips and ties in the chassis.
8. Slide the power supply assembly to the front of the computer and then lift it out of the chassis.

9. Install the new power supply assembly into the chassis so that the screw holes in the new power supply assembly align with those in the chassis.
10. Install and tighten the four screws to secure the power supply assembly.
    Note: Use only the screws provided by Lenovo.
11. Reconnect all the power supply assembly cables to the system board and each of the drives.
12. Secure the power supply assembly cables with the cable clips and ties in the chassis.
13. Go to "Completing the parts replacement".