MVS-4 right audio channel crackle

Joined
Oct 9, 2016
Posts
14
Well ive been working my way through my 4 slot getting things up and running again, and ive come up against an audio issue...

When I got the game, you had to turn up the volume all the way to hear the games, and the right speaker was disconnected. I hooked it back up, and discovered it had a nice crackle in it a certain frequencies. Unfortunately, one of those frequencies is not the sine wave in the hardware test. It sound fine.

So I recapped the board, and this fixed the audio volume problem. Now I just have the crackle left to deal with. The problem is in the right channel only. I don't know if it also is present in the head phones (my head phone/card reader board is missing). The problem appears to be independent of the carriages (it occurs in all games, in any slot).

So now Im really wishing I had a good schematic of the sound section of the board (its an MVH MV4 Board). My best guess at this point is the YM3016 may be bad. Is there anywhere I should look first?
 
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Joined
Oct 9, 2016
Posts
14
Just an update. I was able to get my hands on a combo card reader/head phone board this week, and make myself a wiring harness to connect it to my mv4. The static that I can hear at the speaker is also present at the head phones.

I found the MV1 schematics posted on line, and the sound section appears to closely match what is on the mv4 board.

So I think the issue may be at the YM3016 DAC, or one of the down stream 4558 amps. I am going to order some more parts and start trying to trace down the issue. My shop has cooled down in the mid-60s these past few days, and I have noticed that if I turn on the game, the static doesn't start until it has warmed up about 5 minutes. So I may be able to use an inverted can of compressed air to cool some chips down to try to isolate the problem further.
 
Joined
Oct 9, 2016
Posts
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Yet another update...
I replaced the amp (its a LM324, not a 4558), and that didn't didn't help. So I had to wait for the YM3016 chip to come in from China. Well I got it yesterday, and swapped it in. Still no luck. After the game warmed up, the crackle was back. Next step would be to replace the YM2610. I am a bit nervous about replacing that one. I pulled up one trace replacing the YM3016, and had to run a jumper to get it to work. The YM2610 has about 4 times the number of legs to de-solder. I don't know if I can pull the chip without damaging the board traces.

I am considering sending the board out for the repair. Who is working on Neo-Geo boards these days?
 

DaisyAge

Galford's Armourer
Joined
Jun 10, 2018
Posts
457
Long shot but have you tried cleaning the volume sliders with something like deoxit d5? Give it a good rinse and scrub lightly with a toothbrush and then rinse it with deoxit again. I've fixed a lot of crackling sliders like this, although not for the MVS. Also does lowering the volume sliders a bit while playing get rid of the crackle or is it always crackling even with them turned all the way down?
 
Joined
Oct 9, 2016
Posts
14
I read other posts that discussed the sliders, so last week I cleaned both sliders with a q-tip and rubbing alcohol. It didn't help any. Adjusting the sliders does not appear to make the crackle any bettor or worse.
 
Joined
Oct 9, 2016
Posts
14
So I have a happy ending to this thread...
So I decided to go ahead and replace the YM2610 chip. It took 6 weeks for the pair of replacement chips to get here from China. They were obviously pulls, so I am glad I bought two of them. I went to install one, and discovered the socket I purchased was the wrong size (the YM2610 is a 1.78mm pitch chip, NOT a 2.54mm). I found a guy on ebay who had the correct socket and ordered it. The socket came in today.

In order to lessen my chances of pulling a pad up, I used snips to cut the old chip off where the legs meet the body of the chip. I then used my soldering iron to heat each leg up and pull it out. Finally I used my solder puller to clean out the holes. The new socket went down without a hitch (although you have to be careful on 1.78mm pitch legs that you don't solder two legs together).

I got everything back together, and was able to boot my board into test mode. The board passed the sound test with flying colors (woo hoo!), but when i went to boot into a game, it wouldn't boot. I messed with the board for a good half hour before I realized that bumped dip switch 8 installing the board set into the cabinet. The board was in screen freeze mode. After i felt stupid a while, I booted up Samurai Showdown 2 and played a couple of rounds. I am happy to report the game played flawlessly, and more importantly sounded flawless. Now I just have to find a replacement for the onboard battery, and I will have a fully functional MVS-4.
 
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