Many power supplies have an LED attached to indicate whether the device is powered on. Although LEDs rarely "burn out," they might need to be replaced if physically damaged by a blow. Owners of customized PCs might want to replace an LED with another of a different color to better fit the aesthetics of their design. Replacing an LED is usually straightforward, requiring one to unmount the old LED, disconnect it from its power supply, then solder and mount a replacement.
1). Disconnect the computer from the wall outlet and unplug all peripheral devices.
2). Touch a metal doorknob or other grounded bare metal surface to discharge any static electricity accumulated in your body. The electronic components in a computer are highly sensitive to static electricity and could be damaged by any buildup in your body.
3). Open the computer by unscrewing the case and slipping it off.
4). Unmount the old LED from the case. The exact method will vary depending on the specific model of computer case that you have. Some models hold the LED in place with small clips; others use glue.
5). Clip the power supply wires connected to the old LED with wirecutters. Try to do this as close to the old LED as convenient, to preserve ample wire for connecting the new LED.
6). Solder the new LED to the power supply wires. Make sure the wires' polarity and the LED's polarity matches. The negative wire is generally black, but this can vary by model. Consult your motherboard's manual if in doubt.
7). Mount the new LED in the case. Depending on what kind of case you have, you may need to use clips or glue.
8). Screw the case back on and power the machine up. Check the LED to make sure it lights.