faulty PSU or board? Any other possible cause?

I tried different permutation with seven PSUs and 2 logic boards, and I still encounter the one-green-led-only syndrom. I suet ther must be another possible cause of problem.

Anyone has any suggestion about what to try and replace next?

I have my digidesign home studio all set up and stable after many years of trial and error and ther is no way I will upgrade to start again from scratch into the mayhem.

Help much appreciated