Look Familiar!?!?!?!
Anyways. I did the MKIII X-Clamp replacement, and that helped for about 2 months. Now for some reason its back. I had a short bout with black screens and a 3rlod, but those seem to have passed very quickly and once again I have a what I like to call artifacts/ color distortion problem. Now that I think about the 3rlod, I think I caused that and the black screen could have very easily been my fault too....the hdtv/sdtv switch diddling.
Here are the different recommendations I have received:
1) X-Clamp Replacement (Check)
2) Fan Shroud Mod (Check)
2) Heat Gunning
3) Bad SMD Capacitors on the back of the CPU and GPU areas.
I've checked my SMD capacitors by eyeballing them up close, and they look okay. My temp is pretty darn high, but I don't think thats what is causing it. I've done reasonable measures to combat heat, new thermal paste = astounding heat transfer and the shroud mod has made my GPU fan much hotter than the CPU fan. (I'm not 100% sure, but heat just doesn't seem correct with the testing I've done.) Yet tonight, the momemnt I put my case back on, it came back after alot of testing with everything out in the open. I've done the RBJTech Shroud mod and still no go. I think I'm going to try heat gunning it tommorow.....maybe...see how I daring I feel.
I don't have an answer for you, because I'm still scouring for one. How about you quick grab a heat gun and give heat gunning the GPU/Mem/South Bridge a whirl and report back.Remember, tin foil everything except for GPU/Mem/and Southbridge..set for oh say 750F and toast for about 2 minutes in circular motions. Let sit for 30 minutes until cool. But if you do heatgun, an MKIII RBJTech would be essential too...or it would probably be pointless and the problems would come back (supposed bending of BGA packages and solder joints.)
AFAIK the towel trick....could be bad, heat gunning is the better alternative. As I read the forums, I'm seeing more and more of this problem. I think its related to the no video problem, because i've experienced that once or twice but mostly just color prob.
Oh, I've also tried pressing on the front ram chips/southbridge/gpu heatsink firmly with my finger while Gears was running, and I didn't notice any difference in video or a start of artifacting. Now this was when the problem was not occuring, but you'd think if the problem was bad BGA, pressure on these likely candidates would cause something to happen. Now all of sudden heat and SMD capacitors seem more likely. More testing tommorow I suppose.
That's weeks/ quasi months of battling this problem, so you've got a headstart. Hope it helped a little.