Focus great in center, not great in corners

TheShanMan

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So after struggling with a tube swap (thread here) I decided to move on to doing a tube swap with a different chassis (k4900) and tv tube just to see how that experience would compare.

Only change from my normal procedure is I used the rings from the arcade monitor because the tv's yoke and rings were one piece.

This time it went amazingly easy. Purity was easier to dial in. Convergence was almost dead on from the start. The ONLY problem is diminishing focus as you go from the center to the corners. Center is dead on but while I could probably live with the mediocre (at best) focus in the corners, I compare it to the original monitor in my cyberball (it's a dual monitor game so it's handy for monitor work) and that one has focus that is dead on all the way to the corners.

I adjusted focus on the fly, and adjusted the cutoff pots to minimize the effects. In one corner red is the predominant problem and in another green is. I have also rejuv'ed the tube, although I wonder if I might need to hit it again? I've never had focus problems before so I'm not sure to what extent, or by which procedure, focus is improved with a rejuvenator.

I might end up putting this in one of my less loved games and I can be happy with it there, but the picture is so sweet otherwise that it seems a shame not to be able to give this to one of my most loved games.

So is this a mark of a poor quality tube? Or is there something I can do to improve the focus at the perimeter?

Ignoring the fact that convergence is out a hair in the 2nd pic (corner of monitor), look at one of the dots in each pic. In the 1st pic, a dot is made up of 3 red lines and the average height of the lines is relatively short. In the 2nd pic, a dot is made up of 4 red lines and the average height of the lines is quite a bit longer. And from a practical standpoint, you can see that the text in the 2nd pic is readable but far from ideal. This crosshatch is red/blue only btw.

2010-10-26ConvergenceProblem001.jpg
2010-10-26ConvergenceProblem002.jpg
 
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