When a computer fails to boot, most users immediately blame the motherboard, the RAM, or the hard drive. However, the true culprit is often the most overlooked component: the Power Supply Unit (PSU). A faulty PSU can masquerade as a multitude of other hardware failures, causing instability, random reboots, or a completely "dead" system.
Compare the numbers on the screen to the standard voltages: pc power supply checker
Plug the PSU into the wall outlet and flip the switch on the back of the PSU to the "On" (I) position. The PSU should instantly power up, and the tester screen should illuminate. When a computer fails to boot, most users