I'm an old Gamer, looking to get back into Atari, so I bought a tele-games heavy sixer off ebay for like $30, I plugged it up, it works fine until about 3 minutes after I start playing, at that point the screen starts to fade and become extremely dark, still visible, but barely. I had taken it apart and cleaned all the major components, with alcohol, microfiber cloth and detailing brushes, and also cleaned up the connections in the cartridge slot, RF cable port, etc. I have also ordered a new RF cable, in case that's the problem. I just thought I'd throw this up in case this is a pretty widely know issue that I can save some time troubleshooting by drawing on the experience of those more seasoned in these regards. Let me know what you think, and thanks for listening to my ramblings.
GG