We have a 27" Hitachi TV. Lately, and it seems to occur only in the evening, between 8:30PM and 11:30PM, the picture gradually becomes very snowy and eventually, the picture disappears and becomes totally snow with the accompanying sound of 'snow'. The remedy we have discovered is to strongly bang the side of the set with an open palm. This clears the picture and the sound immediately. However, the clarity only lasts for a minute or two and then the whole process begins again. We are almost at our wits end! Sometimes the TV is on during the daytime hours for quite a while and none of what is described above occurs. It's only after dinner when we sit down for a relaxing evening of television that this happens. Can anyone suggest a more permanent remedy? THanks!

It it your coax input, unscrew and scrape center conductor, if not there, it will then be likely to be in set. Eleminate any add ons(VCR,DVD,etc) so you have signal and set.
Since you lose both, is why I said coax?