Quick & easy method for testing your power supply Helps you easily diagnosis problem source Help prevent accidental damage to your computer made from aluminum for better heat dissipation Power Supply Tester allows fast & easy tests for your power supply. Just turn on the power supply & plug in a 20pin connector HDD power connector P4 connector & FDD connector one by one to check 3.3V 12V PG -5V & 5VSB output. Green LED signal indicates PASS. Helps you easily diagnosis problem source & prevent possible damage to your computer