I bought a Sapphire R290 Tri-X recently together with a seasonic 450 watt PSU. I plugged in the PSU, connected the 6+8 pin from the PSU to the GPU and replaced my old GPU , a 4870, with the R290. Now I don't get any video signal when I start up , and even after the start up (1-2 min later on) I dont get any video input! Is the card broken? Is my logic board broken? HELP!!!