In my case it appears it was a crap PSU. I have that A2 working right now, running 1200, but I am only getting 88mhs out of it. It's running great, I was going to work on changing the other settings this week. BTW I had to plug in the power to the blades backwards in order for it to work.
On my other one, it works and runs for a little bit but then powers off. During the time working, it starts out at 88mhs then slowly dwindles down to 6mhs then it powers off. I am assuming I have bad blades or something.
i had the same problem check to make sure that your NEW pusu PCI-E ooutputs match what is on the orignal PSU. If you look closelsy some of these are flipped lukcliy the miner board is smart enough not to provide power when the pins are reversed.
I good way to bring an A2 back to life is unplug all the blades and plug in power to board and see if it starts.
Then plug in power to a single one start the machine , flip PCI-E if the A2 won't come back on rinse repeat