Test ATX 12v 2.0 power supply. Quick and easy to test 3v, 5v, 12v Compatible: Molex connector, P4, Floppy, S-ATA, 20-pin, 24-pin. If the power output is working, the LED will light and you will hear a sound, if the power output fails, you won't see the LED light & no sound. Built-in load generates steady output.