I can't even get to the screen to adjust frequency, with everything blank on the main screen.
Yes but you are using 2x PSUs without power distribution. So you have 1 PSU connected to 2 boards, which could take up to 1050w. 425w is not necessarily enough to boot up 1 board if they are specified 525w each. I have power distribution circuit boards, so I can use 2 PSUs on the same board..
Try disconnecting all hash boards, and only boot up the control unit only. Then configure to low clock, then re-connect everything and power on again.
But if you mean blank, as in White page, no menu, can't click Configuration at all, then it sounds like you lost your firmware.
If so.. Then no clue what to tell you... Can you get SSH access?? If so then possible for someone here to send you a copy of the firmware if you trust it for no viruses .. LOL
Bitmain has not posted a copy of firmware yet...
Just thoughts