i actually think its simpler than that. if OP hasnt done so, he should use the video reset technique and use a composite cable to attach to the tv for testing purposes. if this still fails then a proper reflow with cpu/gpu plate removal and flux will hopefully do the trick, otherwise its a parts machine but dont give up yet.
the video technique works for me when my machine is in fsm and it wont display in either hdmi or component but it does in composite. i know its unlikely but you never know.