Xbox has no picture"

Hello my name is Tim Ehrhart and it sounds like you have a cold solder short on the gpu. You need to use a heat gun to heat the processer up to reflow the solder. You need to shield the caps ( tall parts on the pcb ) from the heat as if they get too hot they pop. You cand see the solder you are reflowing as it is under the GPU processer chip ( the one under the short heatsink ), but it wouldnt hurt to reflow both processers. I hope this helps you, it does for me.