BB2 Power Comes on for 1 second then shuts off

[Dirtguy]

I am trying to figure out what is shutting down the power when I turn the machine on. When turned on, all green lights on MB flash on, then power shuts off. I tried this power supply in another machine and it works fine. I narrowed it down to the 24 volt 4 pin connector. If I unplug it and turn on the machine all green lites on mb  stay on power stays on. Plug in the 4 pin connector and everything shuts off. I tried a different backplane, different CPU, unplugged the printer, BV, tried it with screens and button panel disconnected. What else should I be looking for or try. What all does this 24 volt run? As I said this power supply does work in another machine. Just got this machine, never saw it running.
                                                                                                                      Thanks

[rickhunter]

You may have a harness that is shorting out stuff.  Unplug all the peripheral connectors from backplane and leave only the power plugs from the power supply.  Power up to make sure it stays up, if it does, power down, and plug in a connector, power up and test, etc.  Make sure you power down after you test and before you plug another plug.  Do not plug cables while power is up.

[Dirtguy]

will give that a try and get back with results

[Dirtguy]

Found the plug that is causing the problem. It is labeled B/H and plugged into Aux Power 1. Its an 8 pin Molex. They have it wire tied to the pigtail that has the two top plugs into the PS. Tried to follow it up but without cutting all zip ties I can't see what it connects to. Without it plugged in, I can clear and set all settings but game won't come up cause oled button panel error. Any idea of what this plug runs

[rickhunter]

I believe that goes and power things in the topbox.  I'm not entire sure, you can try and trace wires to the side distribution panel (the area where the monitors get their power from).  You should be able to find it there.