NEO GEO MV-1A Button issue

[Nik73]

The New Astro City cab that I ought recently came with a MV-1A one slot motherboard. At the weekend I figured what the heck and ordered a 138 in 1 cartridge. I'm still in the middle of restoring my NAC, so thought I'd try it in my Jamma cab.

It's my understanding that one slot mobos are Jamma compatible and should just connect straight to the Jamma connector without any mods. The cartridge works fine, but some of the buttons are messed up. 1P button B doesn't work at all, but 2P C is that and 1P B at the same time?? Also 1P B is 2P C as well. Hope that makes sense. Also, I can't find a way to quit out of the game, which should be !P and 2P for 3 seconds.

Any ideas what's causing this? I've tried it with just the motherboard and the hardware test, but it's the same, so it's obviously an issue with the motherboard. I just have no idea what. I've also cleaned all the connectors, but no change.

Everything else I've tried in my Jamma cab works fine.

Thanks in advance.

 

[pulstar]

I'm not sure if the 1A has a NEO-C1 custom, but this controls the inputs on some MVS.

I would trace back from the JAMMA edge and see where the signal goes and then check that component.

 

[Nik73]

Thanks Pulstar, I've had a look and can't see anything out of place, but I don't really know what I'm looking for. There's a few bent legs and some muck, but nothing glaringly obvious.

After taking it to bits, it's actually a 1-FZ.
I've given everything another good go with contact cleaner, but no change except the 1P + 2P does exit the game now.

I checked again in the test mode and this is how all the buttons are messed up.

Press 1P does 2P

A B

B(X) C

C nothing

Press 2P does 1P

A nothing

B A

C nothing

I can't find any info on this being a common issue, or an issue at all. I could live with it as only play 1P games, but there's no way to get the B button to work. Appreciate any help.

 

[penrhos]

Use a length of wire connect one end to gnd and tap the edge connectors for buttons 1-4 and see what the results are.

 

[Nik73]

Thanks Penrhos. After some research and testing, it seems fixing this is well beyond my limited capabilities. I was hoping it was going to be something really simple like clean this connection or........Well, that’s about it.

 

[Flinnster]

Yep, I would inspect this area here for damage:

But yep, changing the NEO-C1 surface mount chip is not trivial, definitely need some skills (and a suitable donor board for the chip itself)