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How much overscan is safe on a CRT?

Discussion in 'TVs' started by Zacabeb, Mar 24, 2004.

  1. Zacabeb

    Zacabeb
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    I have a question for those with hardcore experience of deflection circuitry and CRT's.

    I have a few video games that suffer from less than decent PAL optimization, and do not have a 60Hz mode to make up for it. One such game is Ridge Racer V, a game which I cannot really dislike no matter how hard I try. In that game, neither is the picture scaled or expanded to fill the screen in PAL, nor is the geometry in the picture corrected. So it's not 'free widescreen' as some would call it, but a squashed image where everything is bloated.

    What I've tried a few times when playing the game is to compensate for this in the geometry settings, by increasing the Vamp until about 460 lines are visible (normally I keep the geometry adjusted to display around 536 lines, the least overscan you can reasonably get out of this set).

    When doing this, of course a lot of the picture doesn't land on the shadow mask, but way outside it and directly on the inner aquadag in the CRT. Of course, these parts of the picture are black aside from the AKB pulse at the top of the picture, so there is little current between the screen and gun. However, the current is raised in the deflection coils when doing this perverse overscan trick.

    Would someone here with deep knowledge of CRT's and deflection systems advise against this, is there a risk I will cause damage to the deflection circuits in the set or the CRT using this much overscan? I have seen some sets that can do the same thing at the push of a button (and do increase Vamp) to make letterbox images fill the screen, and end up with about the same perverse amount of overscan, so I guess it is not entirely dangerous for a set to do this. Better safe than sorry though. ;)

    The set in question is a Philips 32PW9616 with the infamous Panasonic Quintrix F tube.
     

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