White dot

Is there anyone reading this who has (or has a granny who has) a really old TV, such that when you switch it off, the picture collapses down through wibbly-wobbly horizontal lines into a white dot, which if you look at it for long enough may split into separate red, green and blue dots as it fades away?

I'm feeling nostalgic for seeing that, and can't find any videos of it online...