I don't know what's going on, but I've a set here showing what looks like exactly the same effect, and wouldn't you know it's my KV-1800UB! I'm sure it looked normal enough when I was using the TV for a spell about 20 years ago, then it sat forgotten in a corner of our front room in County Durham, and I only noticed the speckled tube when placing the set in the bedroom here after our move at the start of last year. The front room in Langley Park had mild to moderate issues with damp, if that's relevant.
Paul
Paul
