Chester Copperpot

Hi All... So, I finally got a new power supply to try hooking up the CX2600A that I bought at a garage sale almost 20 years ago and have been carrying around from apartment to apartment... The good news - it basically works! The bad news - it has a really nasty "beat" that's causing audio and video trouble. I put a video up of it here: https://www.youtube.com/watch?v=wxAIub4ymRA I don't think it's the power supply, I just bought a brandy-new one from atariguide.com and the actual hookup to the TV is via one of those RF TV coaxial F plug female adapters. So both of those should be good. It happens regardless of the cartridge I put in, and whether I use channel 2 or 3. The games seem to run fine (at least, for as long as I can stand to play them with the terrible noise.) Any suggestions? I've got a soldering iron and I'm not afraid to use it! Just need a little guidance. Thanks! -Chester