A3000T Help

[Motormouth]

Is there a problem with one of the 12 volt lines???   How is the ATX power supply adapted?
Do all of the expansion boards show up in early startup?

Is the mediator's power input set up properly ?

[Motormouth]

... Have not tested under load. ...

I would try to test under load, and feel if the connectors on the ATX adapter ends (either the motherboard side or ATX side) are getting hot.  This may seem like a little thing but this could be something as simple as a continuity problem.

Also do you have another ATX power supple to try?  Some of the older or  cheaper supplies have issues with proper voltage or noisy voltage.  I don't know how sensitive the A3000T motherboard would be.

I also suggest looking for blown Caps on the A3000T.  The old power supply may have damaged a cap or two when it blew.