Posted by scott oberg on September 21, 1999 at 13:25:35:
In Reply to: Monitor Problems... posted by Chazz on September 21, 1999 at 12:44:15:
You're at exactly the same spot I was in my project a week ago. I pity you... ;)
The problem essentially is... is the problem with the Video Card? The cable? The monitor? The software Sync rate? Who knows. The key here is to eliminate the options.
Firstly, the cable is the easiest to get right. I built one by cutting the end off of a VGA extension cable, and wiring it to the Monitor RGB sync and ground leads. I identified which VGA pins were required by looking at a chart at 'The Arcadium' in the links section here. Essentially, RGB, Vsync, Hsync, and a ground (pin 5) are required. I ensured that I had properly identified the monitor leads by tracing them back to the JAMMA connector, and comparing what I believed them to be against a JAMMA pinout diagram (I don't have a URL, but it might even be on this site...), because sometimes the colors of the wires don't mean squat. I traced the VGA pin to it's proper wire at the other end by using a multimeter and comparing resistance. It's the easiest way to ensure that you're using the right wires. Once I was satisfied that I had that part right, I trusted it. BTW- I got an entire screen of a single color when I attached a sync wire to one of the individual colors (I eventually used this technique to set the color purity on the monitor). This says the cable *could* be improperly designed.
Secondly, is the video card. There is a partial list of vid cards on Brian's PC2JAMMA page. The key thing here is to avoid S3 chipsets. (most Diamond cards, but look at the card: It will usually be stamped on the big chip in the middle). If you're in doubt, try a different video card. It also doesn't hurt to run a video diagnostic utility (someone here mentioned one before, and I used it.. it freed up a bunch more possible resolutions/ sync rates).
Thirdly is setting the sync rate in arcadeos. I couldn't figure this out for the longest time, that not all monitors are created, or sync, exactly equally, and the slightest adjustment can make all of the difference. Here are the important things to pay attention to: in arcadeos.cfg, you must have incabinet=1 or whatever the 'arcade' setting is. Secondly, you may have to fiddle with the NTSC fine tuning, which is a few options down. It looks something like H_Sync=105 and V_sync=5 as default. Unless your picture is 'flipping' in a way that suggests that the V_sync is out, fiddle with the H settings first (and maybe only). You can test this theory by adjusting the v hold on the monitor: if you can stabilize the pic, forget about v settings for the time being. I changed H_sync to 107, and it synced properly. The key to remember here is that a LARGER value is a slower sync, therefore you should adjust up- also, you should adjust 1 setting at a time, and the answer should normally be between 107 and about 115 on the outside. Hopefully, at this point, you have an image, despite how distorted and discolored it might be.
Lastly, is the monitor. I left this for last, because I believe that the real problem is rarely the monitor. I know that, at this point, you're wondering if the damn thing works properly, but trust me, It probably does (will). The discoloration, etc can be adjusted, removed, and improved at this point. Your 'blue screen' (kinda ironic), might have to do with a color purity issue. Check a message to Pac a little ways down for a link to a *very* good document on adjusting monitor Yokes and adjustment rings. You'll be surprised how much affect you can have on the quality of the image.
I hope this helps to get you there.
: Is there a way for me to check that I have everything wired properly? I'm getting a image that is very distorted (really bright blue, and horizontal way off). I've been playing around with the adjustments for about a week but I haven't been able to get a clear picture. Any sugestions, or does anyone make an conection that I could just plug into my video card and solder to my JAMMA board?