If you have a motherboard that expects the -5 volt signal instead of the +5 volt signal, and you build the reverse polarity circuit (cable) as shown
here , you may end up with the power supply starting and then stopping a few seconds later. This is caused by the cable you created was plugged in incorrectly. The single wire goes to the MB power On pin which is the pin that is closer to the center of the board. The other cable then plugs into your motherboard.