CBS Columbia tv shut off question

[radio nut]

I always meant to take a video but never did, after running my 1950's tv ...when you shut it off after about 5 seconds the screen had what looked like lightning going random directions on the screen for what seemed to be a solid ten seconds or so. Not continuous but here and there. It was quite cool to watch and it needed to be very dark in the room to notice. Has anyone else had this happen?