When I plug in my power supply to the ATX_12V plug why would it cause the computer to shut down?

Question

When I plug in my power supply to the ATX_12V plug why would it cause the computer to shut down?

Answer 1

problem with the smps.

Answer 2

Sounds like a short in the system, causing a protective shutdown. What device are you plugging in that restarts the PC? Check for crossed wires or a place where a yellow (check for red too) wire is touching the case or a black wire.