Did you try switching the controlboard to hashboard cables to check if it is OK?
Discussion
Yes, that was one of the first things I tried. Also used a different port on the control board, turned the cable around, and measured PSU voltage (is OK).
The repair manual talks about "power output terminals" on the hash board, but I can't find anything that looks like that. Why would a hashboard even output power? Or do they mean INPUT?