At some point though it becomes impossible or at least impractical to repair. Like, once it doesn't work, because N64s are dirt cheap and it's probably more effort than it's worth to fix one. Especially since one of the essential special chips might be fried. Usually, when you have the jumper pak in, cartridge in, AV and power wired correctly and it doesn't work it's fried. It could be sleeping, so wait a week or so before you junk it. I think the number one cause of N64 board death is crossing the 3.3V and 12V power lines.