So I finally got around to testing a TI-99 that someone gave me about a month ago. After getting everything in order, I was to able to get a picture and start a cartridge game. Everything seems to be working, but there's a heavy crackling/static noise in the background. It's not louder than the sounds of the TI-99, but it's definitely noticeable. What could cause this? Is it something internally wrong with the TI-99, or is it just a weak connection between the switchbox(es) and/or the console and/or the TV?

Thanks in advance!