Sega JAMMA IO board help! Stuck inputs?

[andynumbers]

Recently picked up a REV.A 838-13683-91 JAMMA JVS IO board, and I'm getting stuck inputs on the test screen. Specifically the stuff that goes to CN3 (buttons 6,7,8,9) for 1P and 2P. Inside a 6 button game (CvS2 for example) button 6 is registering as stuck on.

I noticed that the BA6212 chip next to CN3 had been messed with. Some of the pins were cut by the previous owner...I guess in a futile attempt to fix the problem. I desoldered the chip completely for now, but no changes.

There is no effect if JP1 is changed between A and B positions.

Any ideas? The rest of the IO works fine.

 

[LazerFlux]

I'd start by putting everything back to factory if you can.
Following that, I'm not entirely sure what the problem could be specifically, but I would start by checking continuity or voltage back to the outputs on the IC's. There may be a logic IC or multiplexer as well that could be an easy replacement.

Do you have another I/O that you can use to test with your setup to test?

I think it's worth it to try and repair, however absolute worst case, I have a NOS 838-13683-91 I can sell you for a not obscene price.

 

[andynumbers]

Thanks for the response!

I have ordered replacement chips for the two highlighted in the attached picture (shamelessly stolen from someone else on this site, sorry!)

I am hoping this may fix the issue. I do not have another one of these boards, but I do have a working Capcom IO and a Sega JVS IO from a Naomi Universal. Both of those work fine with my Naomi netboot setup. If this doesn't fix the issue I'll probably just put this on my scrap pile. I only paid $25 for it from eBay as an "untested" board, so no big loss. I can still use it for games that use 5-buttons or less.

 

[andynumbers]

Here are the actual pictures of the unit when I first got it (from the ebay listing).
It looks like the previous owner attempted to solder button 6 for 1P and 2P (probably for CvS or MvC2)
Some pins were cut from the BA6212 chip. I assume the previous owner attempted to "fix" the stuck input.
The hot snot was since removed and the chip has been desoldered.

I also noticed, mine says "Auto IO" next to JP1. Not sure what that means, but I don't see it on the picture of the other unit above.

 

[LazerFlux]

Let us know the result!

 

[andynumbers]

Update on this: no dice. I got the replacement chips in today and they had no effect. I think the CN3 port is stuck in output mode rather than input mode. Not sure if it's a problem with the main microcontroller chip or something else. At this point I think I am throwing in the towel.

 

[mR_CaESaR]

I've got EXACTLY the same problem on my Rev A. I'm waiting for a Rev B to see if that fixes my issue.

 

[ROBO84]

I've had this with the normal JVS io, these look a little different but I guess the setup will be the same, if you look at the edge connector you'll see a resistor that goes into an opto, the little beige things, on the normal JVS they fail short so the input will be always on, see if you can read the part number on it and get a data sheet, you can test them with a meter on continuity fairly simply. I managed to get some spares from ebay, a bit fiddly to swap out as my eye's ain't that great any more!!