Screen is black - new poweer supply

I have a 30" HD Cinema Display connected via DVI (as third monitor) to my mac pro. It would go off and then on when I disconnected video plug to power supply and then reeconnected it. NOw it is black all the time. I replaced 150w power supply. Still black.

Maybe needs new cable (the one with multiple leads) but don;t know where to get one. Any suggestions?