X box 360

My 360 like so many others out there has taken a $500 crap on my livingroom floor.It started out freezing in online play.Eventualy it stoped working and i got the three lights (ring of death).I did a good deal of research on this matter and found a salution (or so i thought). It seems the GPU and CPU are the problem the heatsinks on top of them are not clamped down hard enough(or a relitive problem dealing with the CPU and GPU).I tried a few differant things before I stumbled on a fix that can be found on youtube (heatgun fix).This was, I thought the end of my problems. Once I had finished I put my 360 back together, and glory be the gods it worked,my game started up I saw somthing I had not seen in 8 months the x-box symbol. But just two short days later i moved it back into my livingroom pluged it in and, there was sound but no picture. I checked the plugs and tried again and now I have the three rings back. And no picture. If anyone has advise would be more than happy to listen.Thanks