Only sound effects on a MV1ACHX board

Relo

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Mar 14, 2015
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Like the titles says, I can only get some sound effects on the MV1ACHX I recently bought. Sound doesn't work in the test mode and music also doesn't work. (I only have puzzle bobble to try with)

Beyond that from looking at the board it's missing the NEO-BUF and is bypassed with wires, and the BR6216B-10LL seems to be replaced with the HM6116LK-70 and is socketed.

What could cause only sound effects to work? And how can I get music and the audio test to work?
 

DaisyAge

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I know for a fact that the ACH(X) boards are some of the worst made. They were manufactured in China and are prone to a lot of issues. I had one myself so I know first hand. Can you post some pictures of the socketed chip and the bypass? I know there are flex patches for the NEO BUF floating around somewhere and I would definitely replace and wiring job with one of those if you have the capacity to do so. I'd also head over to the NeoGeo Dev Wiki and find out what chips are related to audio processing (start with the z80 page it references NEO-D0 and NEO-C1) and see if you can find any shorts, damaged traces or vias, or corrosion. Also take a look at the cartridge connector pins because audio issues can arise from a dirty slot. If you haven't already, clean the cartridge slot and the games pins -Plenty of tutorials online for this- NO BRASSO. Also clear the backup ram and see if any of that helps. You can clear the ram by either flipping all the dips on and powering the board and it will say work ram test or the like, leave it for a minute and then power off and reset the dips. Other wise go to the hardware test screen and flip through till it says press A+B+C to clear back up ram. Lastly, how is this board powered? Is it in a cabinet or supergun? Is it 5v modded or the original 12v mono?
Like I said, some pictures will help immensely, try to get clear bright shots on something that can do higher resolutions and upload a photo set to imgur. I will be more than happy to help you get this thing working.
Cheers!
 

Relo

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https://imgur.com/a/AqkXm4G

Already tried cleaning the cartridge connector and cart (though I'd expect that then the test function would work without a cart in). Clearing the ram had the same results, nothing changed. Have looked for clear visual indicators for broken traces, corrosion and other clear damages but with no luck, will go try with a multimeter later today.

Board is powered by a supergun using a PC power supply without a 5V mod. Which works fine for another board I have (misses right audio channel and isn't in the best of shape anymore due to loads of attempts at fixing it, I have really bad luck with buying MVS boards it seems). Aside from me having formerly installed a stereo mod for testing it's the way I got it from the seller.
 

DaisyAge

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Hmm well looking at it I'm not sure what wrong. That NEO BUF is disgusting though. I thinks its worth a few bucks to try out this furrtek board: https://www.tindie.com/products/furrtek/neo-buf-replacement/
I'll look at the wiki some more today
I'd inspect the YM2610, Z80, C1, and D0 for continuity on all pins. I'd go maybe 2 or 3 steps down the line or all the way to the cpu if applicable
 
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Relo

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Mar 14, 2015
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That neobuf is indeed awful, but looking at the continuity and looking at the neodev wiki does seem fine. Certainly should be replaced if I can get this board to work properly.

I couldn't find a C1 chip, but as far as I can tell the YM2610, z80 and D0 pins are all fine. I couldn't follow traces that disappeared under IC's or, presumably, directly go under the IC.
 

Relo

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Don't have an oscilloscope. Caps look fine, no clear bulging, leaking or corrosion from leaks.

I have found some rust though, on the YM2610, some of the pins are slightly rusted. Weirdly enough no where near the solder but on the bend between the package and solderholes as if some kind of anti-rust plating was removed.

https://imgur.com/a/zctb4WZ
 

DaisyAge

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Hmm well then I'm at a bit of a loss as it's hard to tell without having it in front of me. I would give as many of the dip packages as you can a good resoldering. Just use some flux and add a bit of solder until its molten. Do it for each pin, possible there's a cracked solder joint somewhere. I also thought I saw something brown on the edge of the NEO-F0 pin 33. Wouldn't affect the audio but you never know.
 

Relo

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The spot on pin 33 of the NEO-F0 was just some really old hotglue it seemed, could easy pull it off with my nail in one chunk.

I did reflow all the dip packages, now I just get a load of noise, which sometimes disappears, and sound effects. Based on what happens at the sound test, that noise is the "music" at as the noise is going on and off at the same rate as the beep tone.
 

DaisyAge

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I'd say that's progress. I would guess it's either the YM2610 or Z80. Could you make a diagnostic cart or possibly get a unibios installed?
 

Relo

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Don't know how to make a diagnostic cart. I could probably get a friend to flash me a unibios, otherwise I have to order one from Germany.

Also got a full refund from the seller and bought a new one from Romania, though I still want to get this one working.
 

DaisyAge

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Well hopefully your new board doesn't have the same issue. Like I mentioned, those ACH(x) boards really are the bottom of the barrel when it comes to MVS boards. I never got mine to work either and instead used it as practice to remove smd packages, especially the 68k as I wanted to try the overclock mod for my shooters. Unibios would be helpful because it gives more detailed reports and can even get you error codes that will help you track down the culprit.
 

Relo

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This will be a regular A board, no Chinese model.
When I get the Unibios and shows no error the ACHX board will end up as a spare parts board or I'll give it to a friend that loves a hard project.
 
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