Female coax connector in tv bad? (by 2 users)

tv went to all snow, every channel while in use. turn off/on doesn't clear. I connect from wall, through a cable converter to tv.
Cable co. came, researched & pronounced cable, cable converter are good - problem must be my tv.
They even used my cable to connect to their portable tv & it looks fine.
Picture & sound are fine if use TV for watching DVDs.
I'm leaning toward the coax connector as culprit. Is it possible to replace that myself?
We have a 27" Hitachi TV. Recently, it has intermittenly been going from a perfectly clear picture to a gradually increasing 'snow' state with accompanying 'sssshhhhh' noise. The only way I have found to temporarily eliminate this is to literally smack the sides of the set with force! The snow either goes away for a short while or, sometimes disappears for the entire evening of TV watching. Any ideas as to what is causing this and how to eliminate it?