How to replace the power supply in a desktop computer

The power supply is one of the most common components to fail inside a desktop computer. If you don't mind turning a screwdriver, you can replace a bad power supply yourself and save on repair costs.

Before purchasing a replacement power supply:

- Make sure to buy a power supply that is rated for at least the same wattage as your current power supply.
- Verify that the new power supply has all of the necessary connectors that your current one has. You can either check this visually by looking at the connectors that you have, or by making sure your computer is listed as one of the models that the new power supply is compatible with.
- Make sure the new power supply will fit inside your computer's case. (If the new power supply is compatible with your computer, that won't be a concern.)

To install the new power supply:

- Turn your computer off and unplug it from its power source.
- Unplug all of the cables leading from your computer, including the power cable.
- Open the computer's case. (If you're not sure how to do this, you can probably look it up online. Most computers either have screws in the back that come out, a side panel that slides off, or they open up like a clamshell.)
- Disconnect all of the cables leading from your power supply. Note what component each connector plugs into. You should have connectors for your fan(s), hard drive(s), optical and/or floppy drive(s), motherboard (may be one or two connectors), and the front power switch.
- Unscrew the power supply from the system case and remove it.
- Set the new power supply in the case facing the same way as the old power supply and screw it in.
- Attach all of the connectors. (You may have more connectors than components, but make sure each component that was connected before is connected again now.)
- Close the system case and reattach any screws.
- Plug the power cable into the power supply and then into the wall outlet.
- Reattach all other cables.
- Make sure the power switch on the back of the power supply is on.
- Make sure the voltage switch on the back of the power supply is set to the correct voltage (115 volts in the United States).
- Turn on the computer and verify that it boots up correctly.

(Originally published on FixYa.com, January 2011)