Posted: Sat Jun 11, 2011 9:27 pm Post subject: Arcade CGA/EGA/RGB to VGA board
Don't groan just yet. I know there are simpler, smaller solutions for getting RGB from an Amiga to a VGA monitor, but this is multipurpose.
The GBS-8220 is a multi-input board made primarily for arcade machines to output to VGA instead of buying expensive CRT monitors. It can convert multiple frequency(including ~15khz) CGA and EGA, RGBHV, RGBS, and component at multiple resolutions.
I found this interesting primarily because, with a tweak, I can get many old consoles to look much better on a little 15" LCD monitor I have sitting around than the current composite/SVGA to VGA box I currently have. It got me thinking though, this sounds like it would also work for the Amiga RGB output. Unfortunately, some details are omitted from the converter boards specs, like signal voltages, but I've been looking around for JAMMA specs to compare with Amiga RGB specs to see if it's useable.
Does this look like a viable method for VGA output?
I was thinking the same thing and I would say yes as it states on the website it has composite connections. If it has any lag is another thing though but i think it will work. The only drawback that i can see is that its just a pcb and it will need a power supply i think.
...Yeah, but the one he got isn't quite the same as the one I found on Paradise Arcade Shop's site, with it's dual VGA output... Anyway, it's true, a 5v @ 2A supply is needed, which is pretty easy to come by with one of those multi-voltage AC adapters. But, that removes the necessity to wire up the 5v line coming off whatever I connect to it. I can't imagine there would be an noticeable lag for it to be recommended by anyone and used in arcade machines. The lack of a case just makes it that much more fun. Even more stuff to custom build. (By custom build, I mean I will stick it in an old motherboard box, cut some holes for cables and airflow, and call it good.)
An update: I got the board today and hooked it up to the 15khz RGB on my Amiga 2000, it worked very well. The monitor is a 15" LCD at 1024x768, which is an output resolution of the board, so the picture came out very clean. Had to adjust the POTs a bit for color, but no other settings were needed. I'm attempting to get this working with a Sega Genesis, but I'm running into something where the board is only grabbing a frame and it freezes for a while, the loses signal, then grabs another. The scenes are all very dark, like the luminance is missing...
Not that would be of any good measure. I have a DV cam, but the artifacting from low-light situation and YouTube wouldn't give you a good idea of it in action. But, if you want, I'll give it a shot.
I also need to make a correction to my previous post, it was a 3000, not a 2000. But I was using the RGB out.
After reading around, I found that a recommendation of adding a capacitor to the sync line helps with dark picture. All I had laying around was a 48uf and a 1uf, so I set them up in series and the picture got much brighter. I had to set the brightness on the converter board to all the way up to get a much of a picture before, but now at the default 50 (max 99) the picture is just a little darker than I like.
I also had apparently had built an RGB amp to go inline with the the converter board which I thought was to help with overbright issues when using a Genesis on a 1084/2002 monitor. That is helping keep the colors bright. I plan on getting a set of caps tomorrow to test and see what gives the best result for the sync line.
I cut it up because it kinda ran on, but there is the startup from the board, workbench, a part of a demo, Turrican 2, and at the end, I changed the video modes around to show what they looked like and what interlacing does. It may not be too apparent, but the interlaced modes cause some weird things to happen to the title bars when you move the mouse over them. Also, there may be some white spots on the screen, those are from the Amiga, as they do not occur with other consoles/no input. The board has geometry settings I have not adjusted yet to stretch and center the image on the screen. There's a small space at the bottom of the screen which appears to be unused by the Amiga but gets some garbage in. I assume this is because I set the machine to PAL. This can be hidden by adjusting the geometry.
I also took some pictures of the board and the amp which I added the capacitor to earlier for the sync. It appears that it is unneeded for Amigas as the amp actually made the picture darker.
Thanks for making the vid. I have to say it was handling higher resolutions better than I thought it would - even laced screens didnt look that bad on it. I can see how it is a useful stopgap but I think im going to wait until an indivision becomes available again (hopefully in my lifetime lol).
My GBS-8220 arrived Yesterday, I don't want to fry it or my 4000D so I thought I might ask a few questions. I hope you don't mind me asking.
Is that a 15 pin VGA plug or a 9 pin plug you have hooked up to your 3000?
What pin connections did you use at the plug to the 8 pin RGBHV?
The instructions I have show the RGBHV input scans 30.5-32Khz not 15Khz, is this incorrect?
I have seen posts stating that the Amiga needs resistors to lower the signal voltages so that it can work on with the GBS-8220, have you used any additional compponents?
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