I just can't stop!!

[Kiwick]

My 1979 Philips displays that splotch when i turn it off, but its CRT is as strong as it can be, it's simply a quirk of this particular Philips chassis (KT3), here's a vid of it:
http://www.youtube.com/watch?v=NijEGMxUEOU

I think it has more to do with the lack (or failure) of HV bleeding circuits and/or beam killer circuits in some designs than with the conditions of the CRT.