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From: myers@hpfcdj.HP.COM (Bob Myers)
Newsgroups: sci.electronics
Subject: Re: funny phosphorus illumination after power to tv has been turned off
Message-ID: <17660040@hpfcdj.HP.COM>
Date: 3 Jan 90 19:18:33 GMT
References: <6805@lindy.Stanford.EDU>
Organization: Hewlett Packard -- Fort Collins, CO
Lines: 34

>When I turn my TV off, areas around the center of the screen dance around
>brightly in multicolored flames. It is quite pretty but I can't seem to
>explain it. Unplugging the set has no effect. It still continues for
>about 10 minutes before dying out. Now this is an active flaming that
>changes shape and color quite rapidly. Note: this is not the effect you get
>when turning the set off in a dark room where you can see the whole screen]
>lit up faintly.
>
>The only thing that is possible is that the phosphorus is being bombarded
>by electrons, but how can this be if the power is turned off? Is the CRT
>drawing on capacitors or something?

First of all, it's "phosphor", not "phosphorus."  Phosphorus is a rather
nasty substance that doesn't have anything to do with the light-emitting
chemicals used in CRT screens.  CRT phosphors are for the most part (at least
nowadays) various sulfide compounds.

With that said, I can't come up with a good explantion for the phenomona you're
describing, IF you really meant to say "10 minutes" rather than "10 seconds."
I can certainly understand the tube still emitting considerable light for
several seconds after the power is removed - esp. if the set is the 
"instant-on" variety, and leaves the power on the tube filament at all times.
The "dancing colors" would be caused by "random" magnetic fields as various
deflection and color correction circuits in the set shut down, or by external
fields (if you've got the set next to something with a fair-sized motor, for
example).  However, I'm at a bit of a loss to explain how this would go on,
in a normal, functional CRT, with any brightness at all for the period you
describe.  You sure no one in your house has tampered with the drinking water?
:-) :-) :-)


Bob Myers  KC0EW   HP Graphics Tech. Div.|  Opinions expressed here are not
                   Ft. Collins, Colorado |  those of my employer or any other
myers%hpfcla@hplabs.hp.com               |  sentient life-form on this planet.