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SCREEN BURN ON 25" 4:3 TV

A

Andrew H

Guest
I bought a Philips 25" 4:3 tv yesterday. I was watching SKY Sports News on Freeview and noticed that the bright white section on the right hand side of the screen where all the statistics are looked "dirty" after just a few minutes of viewing. When I went to the menu on the freeview box, the background is bright yellow but there were red patches on the right hand side. It goes after a few minutes when watching another channel, but is this normal? Will it damage the tube? Are Philips' tubes any good? Wished I bought the Panasonic 21AP2 4:3 tv now - this has a Quintrix tube the same as on my Panasonic 28" widescreen. Any feedback would be greatly appreciated. Thanks.
 

Tight Git

Distinguished Member
Andrew,

What you describe is not screen burn!

Due to the internal workings of the CRT, a high beam current (ie a bright part of the image) can cause the shadowmask to bulge slightly.

This causes a purity error until the shadowmask cools down again and returns to normal.

I'm not a CRT expert, but I thought that modern shadowmasks were made of Invar which doesn't do this.

Also there should be a beam limiter circuit to prevent it happening.

Have you, perhaps, got the contrast set very high?
 

Tight Git

Distinguished Member
Andrew,

65% does not sound unreasonable, but you could try it at 50% and see what happens.

(I was afraid it might be 100%, as some manufacturers default it to that value in case the set is put on display. It doesn't do the tube any good but the TV really stands out from the others!)

Perhaps someone with this model would care to comment.
 

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