Typical symptoms of GPU failure are:
▪ Distorted or scrambled video on the computer screen
▪ No video on the computer screen (or external display) even though the computer is on
▪ Computer restarts unexpectedly
▪ Video distortion, vertical lines or no display at all
The failure that is causing those strange shapes on your screen, those feint horizontal lines across the Apple logo on boot or preventing the laptop or iMac from fully booting and crashing as the operating system loads. The failure that shuts down your computer when you run some software that utilises the discrete graphics on the logic board is in fact a faulty graphics chip
No end of heating or reflowing will solve this problem. The only solution is to replace the graphics chip with a newer manufactured one or one that has a newer manufacturing date but is of the same specification as the old one.
We do not do something called a reball. Reballing is done by using infra red to heat up the solder balls on the GPU to reflow the solder. The failure rates on reballing are very high and not to be recommended. If at all possible get the GPU replaced.