Dell ultrasharp blinks on and off

It could be a setting problem, power saver setting, or a mode that the monitor does not really support - things like refresh rate - or actual hardware.

Easiest way is to borrow another like monitor, and say another video cord and see if the problem remains, or if a newer monitor says 'out of range' or similar.

Then, if you have a fancy video card,remove it and use something primitive. Not reading instructions is a big cause.

If its not a setting issue, and as the inverter board is ok; if the above description is correct, reseat the inner board connecting cables.(wood fires and seaside locations) If not that, a lucky guess might be the electros on the logic board.