I got confused with the PSU part(didn't get if it was broken or not), but if it isn't and you really need to do some testing other than with the display itself, I guess you could try plugging an external monitor to it. If you need to recover data from it, use a usb c to firewire with an old MAC and start the iMac pro with the 'T' key pressed down, it will show up as an external HDD to the other computer.