Why do some TVs buzz when displaying white text or background with a lot of white?

Answer 1

withouy getting too technical, and because i dont want to get anything wrong, its in the fine tuneing of the AFC, or automatic frequency control. this can actually be fixed by a professional tech. The tuner gets out of alignment, i guess would be the best word. over time, if its not corrected, it may get worse and you will notice the picture maybe shift a tiny bit or even the whole picture changes colors or tints slightly. I have seen this several times myslef in older sets, there may be another cause, jimbob or tv tim may answer and can verify this. hope this helps.

Answer 2

Picture tube is going out.