I bought a used N64 almost a year ago, and I've been noticing some strange things that happen when the screen goes black (or is very dark in the case of Doom 64) during gameplay. Whenever either of those cases occur, the video feed cuts out for about half a second and displays static before returning to normal. An example of when this occurs is the pre-mission images of single player maps in Goldeneye: as soon as the screen goes black, I get that static screen. With Doom 64, it's even worse, as it happens all the time due to the game's dark environments. I tried replacing the A/V cable, but that had no effect whatsoever. What I have found is that the game cartridge and the area where the power supply plugs into the console heat up pretty badly even after ten or so minutes of use, although I don't know if this is a common problem with the N64 or not. Hopefully I have provided enough info to give you an idea of what is going on, but this is an issue I have never heard of happening before.