I am having the same issue. Mine was used as a HMI for controlling a gas turbine. All I can add that hasn't been said is that mine was intermittent at first. Initially if we left it unplugged for a few hours and held the power button down for 30sec after unplugging we could get it to boot. Diagnostics showed everything was good. It must be a failing ss relay. I have tried an ebay MB with all the old components including the psu and got the 3 red 2 white fault. Which leads me to believe the fault is infact on the MB. So now I have 2 faulty MB. Does anyone have a schematic?