QNIC CGM-2500 (Neo Geo 25" CGA) setup help request.

[Kujako]

Been working off and on on getting the CRT in my Neo Geo "big red" working correctly. It's a QNIC CGM-2500. Getting proper color balance and sharpness is driving me up the wall since of the eight pots (RGB, cutoffs, contrast, brightness) each seems to effect the other. I've tried before without luck to find a setup guide. Anyone have any pointers? Ignoring the V-LIN pot' since the geometry seems OK, is it worth touching the transformer focus pot?

Board has been recapped, but not looked at replacing anything else... original problem was color balance only, after the recap I've not been able to get it setup at all.

 

[teethbee]

I'm about to recap this same chassis in my Street Fighter II: CE cab (3Koam Z-Back). If I discover anything, I'll let you know.

 

[Kujako]

I'm about to recap this same chassis in my Street Fighter II: CE cab (3Koam Z-Back). If I discover anything, I'll let you know.

Thanks. Been working on this thing off and on for over a year now... may just have to replace it, but that's a pain and a half.

 

[teethbee]

hopefully you can figure out the issues! just looked back at your other threads, seems I have a slightly different revision. I did see an untested chassis that looks like yours on ebay recently, not that you need more potentially broken parts, haha.

 

[Kujako]

hopefully you can figure out the issues! just looked back at your other threads, seems I have a slightly different revision. I did see an untested chassis that looks like yours on ebay recently, not that you need more potentially broken parts, haha.

Yeah I've kept my eye out for a chassis to try, but it would have to be known working and recapped for me to bother. Took awhile to recap mine, but really can't say that it helped. The tube may just be too old at this point, but really not sure. I'm outside of my comfort zone on this.

Most setup guides I can find say to start with contract and brightness in the middle and RGB turned all the way down. But when I do that, there's nothing on screen. My main problem seems to be contrast/brightness and possibly focus. Just really not sure what to try. When I look at the color bars (using the Neo Geo Monitor Test Tool currently) I can tweak things so the colors look close to right, with a bit of bleed in white towards red or blue. But then if I display a picture from a game or even the menu from the testing tool it's all washed out because I've had to crank the contrast and brightness all the way up. I feel like I'm missing something, or the whole thing is bjorked.

Might try a totally different chassis... but that seems a bit extreme.

 

[Kujako]

Realizing it's working worse now than before I recapped... so thinking I might have fat fingered something up a bit in the process. May pull the chassis and try to recap it again when I have a free afternoon.

 

[teethbee]

Realizing it's working worse now than before I recapped... so thinking I might have fat fingered something up a bit in the process. May pull the chassis and try to recap it again when I have a free afternoon.

Good luck! I think my caps come in Thursday, but I'm not sure exactly when I'll get around to doing the work.

 

[Kujako]

Good luck! I think my caps come in Thursday, but I'm not sure exactly when I'll get around to doing the work.

Same, it's a major amount of work to get the chassis discharged and onto a work bench. Large ground planes made it hard to desolder the old caps. Thinking I might also look at replacing the potentiometers... some of them cause shakes in the picture when tapped indicating they're not providing the best contact.