Help with 20L4 image distortion

[JaFFa]

Hi All,

First off, Merry Christmas and happy new year to everyone!

I've been playing about over the holidays with my retro gear and I've noticed there's an odd distortion occurring on my 20L4. As images pass through from the right hand side of the screen, they appear wide and then thin down as they reach the middle of the screen. A little bit like there was a static magnifying glass on the right hand side of the image.

I have run the 240p test suite and I do not see the effect on the static test pattern (welcome to correct me on that) : https://imgur.com/a/dnEusm8

The issue is quite pronounced in motion, I was wondering which settings I should be looking at to correct for this ?

Edit : Extra info, I was using an ntsc genesis over RGB when I noticed it.

Thanks,
Dave

[H6rdc0re]

That sounds like a problem with linearity. Can you post a picture of the linearity test patern?

[JaFFa]

Sure: https://imgur.com/a/7yBUdQZ

I've also made a quick video, bit harder to see in the video but if you watch the coin box, you can see it stretches out as it gets closer to the right hand side of the screen.

https://www.youtube.com/watch?v=FvRrb9YNmO8

I'll admit it might not look like much in that video, but in real life it's very distracting when playing games that scroll a lot.

[Josh128]

I hate to say it, but your PVM looks great to me, better than 95% of non PVM CRTs out there. I really cant see the issue in the video you posted.

[JaFFa]

I hate to say it, but your PVM looks great to me, butter than 95% of non PVM CRTs out there. I really cant see the issue in the video you posted.

Thanks, it's def not right to me though in real life.

Does any one know what settings / issues would cause such a thing I am describing? Even if you think it's not too bad

[H6rdc0re]

Sure: https://imgur.com/a/7yBUdQZ

I've also made a quick video, bit harder to see in the video but if you watch the coin box, you can see it stretches out as it gets closer to the right hand side of the screen.

https://www.youtube.com/watch?v=FvRrb9YNmO8

I'll admit it might not look like much in that video, but in real life it's very distracting when playing games that scroll a lot.

Your circles look a little off to me and that would cause the problem you’re describing. On any CRT it’s impossible to have perfect geometry and linearity at the same time. You’ll have to choose which is more important to you.