Jamma harness with CGA input on vision pro LCD

[rymin]

Hey guys.

So I'm trying out a 19" vision pro LCD in a Nintendo cabinet that is using an original DK 2 board pcb, a mike's arcade Nintendo to jamma adapter (with built in video inverter and audio amp). The vision pro has a 10 pin CGA input on it, and I ran the R,G,B, ground, and composite sync from the jamma harness to the correct pins according to the manual and I am getting "no signal" from the monitor when I power up the game. I do hear the initial DK boot sound on power up. Any ideas of what could be wrong and how to trouble shoot? Do I need a special 10 pin CGA cable or should using the wires straight off the jamma harness work fine?

Thanks!
Ryan

[Danny Ogg]

Hey guys.

So I'm trying out a 19" vision pro LCD in a Nintendo cabinet that is using an original DK 2 board pcb, a mike's arcade Nintendo to jamma adapter (with built in video inverter and audio amp). The vision pro has a 10 pin CGA input on it, and I ran the R,G,B, ground, and composite sync from the jamma harness to the correct pins according to the manual and I am getting "no signal" from the monitor when I power up the game. I do hear the initial DK boot sound on power up. Any ideas of what could be wrong and how to trouble shoot? Do I need a special 10 pin CGA cable or should using the wires straight off the jamma harness work fine?

Thanks!
Ryan

Try redoing the connections. If you still not getting any signal, maybe there is something that missing for the connection to work, like a ground signal or something only the right cable will fix. I have had similar problems with my CGA/VGA converter.

[Leonelmizka]

I think it's wonderful for me to know for me.

[KJ4IPS]

You sure that's CGA?
CGA uses RGBIHV (Red Green Blue Inensity Horiz Vert), and you seem to have RGBS (which is normal for jamma).
Some LCDs will sync with the composite sync on Hs or Vs (or both). If that is not the case for yours, you can use a sync seperator[1] to get both for VGA's RGBHV.
If you have real CGA RGBIHV, you need what is effectively a specialized DAC (CGA is actually digital) to get VGA out of that.

[1] similar to a LM1881 used in NTSC and PAL, an LM1881 might even work, but I don't know what standards used for that sync. Datahseet here: http://www.ti.com/lit/ds/symlink/lm1881.pdf

[iankellogg]

CGA is the "term" that the arcade community calls 15.7khz RGB.

My guess is the converter in the LCD is not capable of handling the strange sync pattern that nintendo games generate. Its a problem i run into all the time and only a few converters on the market can handle it. Its been on the backburner for a while but i have a circuit that should fix the problem but i never finished it.

[rymin]

Thanks for the clarification, Ian. I've been wondering about that for a while and hadn't been able to find an answer in such clear terms as I am really new to this stuff. I ended up ordering the cga to vga upscaler to try my luck with that and possibly a scan line generator in the future. It hasn't arrived yet, but my big concern after doing all of this is input lag or how smooth animation is on the LCD. Basically right now I am playing with a 412 in one and it plays ok but can get a subtle choppiness despite almost no input lag and a really clear picture with no weird artifacts I've seen on other LCDs. Perhaps I can use an old computer monitor crt some day down the road.