I work in an Orthopaedic surgery research laboratory and we have a lot of macs. We have three MDD Powermacs, one B&W 350 mHz Powermac, a Wallstreet PB, a 1 Ghz Ti PB, and a couple other miscellaneous old school macs. Before I even started at the lab the Ti Powerbook was having quite a few problems with the display. It seemed that every time the Powerbook got even slightly hot (I’m talking turned on for maybe 10 minutes with just web surfing), the display would become so garbled that it would be illegible and completely non-functional. The only way to fix the garbled mess was to raise the Powerbook on some metal blocks that we had and put a fan to the side of it to keep it cooled. Here’s how they fixed it! Link.