The Power supply (also known as a Power Supply Unit or PSU) is what provides the power for your computer and its various components. From the motherboard and hard drives to the fans and CD-ROM drives, the power supply unit is what fuels the system.
Over time the power supply can become worn out, specifically the fan within the power supply. If this fan sputters or fails to run, the power supply can overheat causing damage to both the supply and the computer components. Power surges can also cause a power supply to fail. And if you want to add more hard drives or fans to your system, you might need a power supply unit with more volts. All of these situations call for a replacement supply.
First you’ll want to shut down the computer and remove all connections including the power supply cord, monitor, and any peripherals.
Remove the computer case and locate the power supply, you’ll see multiple wires running to different devices within the computer case.
Disconnect each connection one by one. Make sure the hard drive, mother board, fans, disk drives, and any other powered component are disconnected from their power supply cable before proceeding.
Unscrew the holding screws on the back of the computer case that hold the power supply into place. In most computers, the casing overlaps the power supply box and the screws can be seen near each corner of overlap. Hold your hand under the power supply when removing the screws to prevent the power supply from dropping onto the other components.
Position the new power supply into place and screw in the holding screws. You’ll want to firmly push the power supply unit towards the rear of the computer inside the case, making sure the fan and plug side are facing the rear of the computer.
Reconnect all power connections to the hard drives, disk drives, fans, and motherboard. Note that some connections are smaller than others, for example a 4 wire connection is used on things such as disk drives that need more power. Also note that some fans and other devices may connect to the power supply unit connections through an adapter. Ensure these connections match up and connect fully.
Use a plastic twist tie to secure extra connection cables snaking from the unit, you don’t want them touching components inside the computer or getting caught in the internal fans.
Replace the case and plug all peripherals back in. Plug the power supply cable in and start up the computer. If the installation went well, all devices will be powered and the computer will start up properly.
Remember to touch your hands to a metal surface outside of the computer to prevent static electricity from harming the computer components.