Quote:
Originally posted by andy
That spot after you turn the set off is completely harmless. Some CRTs do it for some reason.
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Don't know why a color tube would do this. However, this would happen quite a bit with b&w CRTs in older sets; it's caused by the cathode still being hot enough, and the HV filter capacitors having enough of a charge after the set was turned off, to form an electron beam (stationary in the middle of the screen, of course, because the deflection circuits were not operating at this point). This spot could burn the phosphors in the center of the CRT, which is why set owners were often advised to turn up the brightness control just before turning the set off. In any case, the spot would disappear in a few moments, after the caps discharged and/or the CRT cathode cooled.