Greetings - I'm trouble shooting a 2009 Mac Pro for a no power up problem. The apple custom 980Watt delta power supply pinout is proprietary but the major power rail positions are evident. ( +12/ GND... GND/ +!2 ) The center group of smaller pins have two conductors that when shorted together will power on the PSU, which is, I think, the " power on" signal, normally supplied by the mother board. In the process of load testing the PSU on the bench to check the current spec. Does anyone have the full pin out of these center group of conductors? Update... I just did a quick load test on the PSU using a 100watt load on each of the 12V rails and forcing the PSU to turn on with the two pins I spoke of. PSU seems to be working at this load and being when it is put back into the chassis with only the motherboard, front and rear panels installed with the 5VSB led lighting when the diagnosis button is pressed, it seems the the power on signal to the PSU is not happening. It seems either a connection issue on the mother board or a failure of the power on button/ circuit. A schematic would be handy to troubleshoot this.