New Net City screen vignette effect issue

[chriszhxi]

My New Net City screen has this kind of vignette effect with speckle like feeling, rather than discoloration which you can see color tint, it's more a gray or dark mask feeling, kinda like pictures showed below, around corners and left right edges, with speckle feeling, not as dark and obvious as comparing to the picture, more subtle, mostly noticeable on solid colors.

Deguassing won't remove it, I'm wondering is it normal or is there something wrong with the screen?

 

[nonosto]

is it in 15khz and 31 or only 31? What's your combo?

 

[chriszhxi]

is it in 15khz and 31 or only 31? What's your combo?

Both 15/31khz, Toshiba A68LTF356X, PD1843 and PD2367, tried both chassis, no difference, so I guess it's tube related?

 

[nonosto]

I have a very light same isssue only in 31 khz, it's seems a random factory issue.

 

[chriszhxi]

I have a very light same isssue only in 31 khz, it's seems a random factory issue.

It's very subtle, only noticeable on solid colors, might be brightness and color uniformity issues, but with the speckle like feeling I suspect it could be something else. If it's a tube issue, it should apply to all modes, that's my guess though.

 

[chriszhxi]

OK, I probably figured it out. Today I did a yoke swap and playing with the convergence, the vignette effect area did change slightly, then I found it's affected when I adjust the convergence.

I believe It's the color uniformity caused by convergence.

Around corners and edges, you usually get imperfect convergence, which means rgb don't line up well. When forming white or other solid colors, bad convergence causes rgb crossing each other, resulting the color is slightly off, depends on how bad the convergence is.