Some popping in MVS sound

[malignantpoodle]

Hey folks,

MV-2F board.

Started to get a bit of popping in the sound. First noticed it in KOF 2003 if someone lands a hit on the other there is sometimes a crackling to the "thud". Wasn't bad, and it is intermittent.

Then later started to notice in Metal Slug X and 5 that during big explosions there would sometimes be popping progressing to static (sounds a bit like low bass sounds are most affected) as if it's overmodulating or something.

Recapped entire board. Did notice sound volume increase dramatically, also better balance in left and right channels that I hadn't noticed before. Turned volume down to compensate for increase, but still have this popping regardless of volume, even if turned way down.

edit; wanted to add that the popping or crackling never happens with the music, only triggered sound effects.

Reflow solder joints on audio IC components? Any ideas? Checked speakers and wiring and they're fine.

 

[Tyranix95]

...Started to get a bit of popping in the sound. First noticed it in KOF 2003 if someone lands a hit on the other there is sometimes a crackling to the "thud". Wasn't bad, and it is intermittent. ...Then later started to notice in Metal Slug X and 5 that during big explosions there would sometimes be popping progressing to static (sounds a bit like low bass sounds are most affected) as if it's overmodulating or something. ... the popping or crackling never happens with the music, only triggered sound effects. ....

Try cleaning the two inline potentiometers (Headphone and Speaker volume pots.) with 91% isopropyl alcohol and a Q-Tip cotton swabs.

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I have an MV-2F. I had a similar problem with it when I first got it. Very noticeable on my M.S. games and my K.O.F. games whenever a "FIRE" or "EXPLOSION" sound effect went off. Other than that, the system seems to works fine; however, this sound effect problem seemed to get worse over time.

I solved it up by cleaning the gunk, grim, dirt, and other crap that had built up inside the two inline potentiometers (Headphone and Speaker volume pots.) with 91% isopropyl alcohol and several Q-Tip cotton swabs.

I had to slide the resistor side to side sever times because there was a lot of junk inside on the traces--under the resistor head too.

After the swabs started coming up clean. I let the NEO dry. And the sound has been fine ever since.

 

[systmdfect]

Sorry for not adding anything to the thread, but I keep reading the thread title as "Some pooping in MVS sound".

 

[malignantpoodle]

The volume sliders? I shall, and will report back later. I did reflow the joints on those while I had it out. Will clean and see what happens.

 

[Tyranix95]

Sorry for not adding anything to the thread, but I keep reading the thread title as "Some pooping in MVS sound".

And that looks to me like systmdfect thinks malignantpoodle's NEO is making some pooping sounds.

Or the MVS just sounds like crap.

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Heh, just messing with ya.

 

[malignantpoodle]

Well, that didn't get it. Same story.

 

[Tyranix95]

Sometimes, dirty cart contacts can cause sound problems. And sometimes some carts orders on an MVS board can sound problems.

Remove both carts from the board. Clean the cart. contacts with rubbing alcohol and a Q-Tip. And also clean the MVS cart slot contacts with rubbing alcohol and piece of terry cloth backed by a club card or piece of card board.

Then, install one cart and test it to see if the problem persists.

If it does, try moving it to the other cart slot.

Next, try this with the other cart.

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If that does not work, find a pair of head phones. And hook it up to the Headphone Jack. Find out if the popping and cracking noise is coming out of both the cab. speakers and headphone speakers or if it is coming out of just the cab. speakers.

 

[malignantpoodle]

Aye, have done this. Carts and slots are ultra clean and it persists in either slot.

 

[Tyranix95]

The NEO outputs sound at two stages: (1) the HEADHONE stage and (2) the SPEAKER stage.

The Headphone test will give you an idea how far up the audio chain your popping and crackling is occurring.

 

[malignantpoodle]

Yeah I'll try the headphones next. But regardless of the results it won't tell me what to do really.

edit; tried headphones. Still has the popping. Think I'll reflow the audio ic points. If it's doing it on headphones it's likely not the amp then.

 

[Tyranix95]

...tried headphones. Still has the popping. Think I'll reflow the audio ic points. If it's doing it on headphones it's likely not the amp then.

Makes me think the problem is at the audio processing level.

Now would be a great time for a chip master to come in.

 

[malignantpoodle]

Well, it'll be either that or the other non-electrolytic capacitors. I could just go and replace the other style caps (easy and cheap to do), but I'd have to get some first. Aside from that it really couldn't be anything else but an IC. In any case, thanks for going over this with me.

edit; the pop is only at a certain frequency, and it isn't all the time. That in and out has me thinking maybe it's not an IC. But who knows...

 

[Xian Xi]

Sounds like you need to change some caps.

 

[Tyranix95]

Sounds like you need to change some caps.

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[malignantpoodle]

Sounds like you need to change some caps.

I'm assuming you mean other than electrolytic? Already recapped entire board.

 

[Prairiedillo]

Did you change out these caps listed in this cap kit?
http://www.arcadecomponents.com/f/Neo_Geo_Cap_Kits.pdf

I stock a bunch of audio cap sizes for Neo-Geo. Let me know what you are looking for as they are clearly labeled.

 

[malignantpoodle]

I have. I've replaced every electrolytic on the board, even the few not associated with the audio section.

 

[Xian Xi]

Did you check continuity from the cart slot to the Z80 and also the YM?

 

[Xian Xi]

Have not done this, but I can. I have my doubts that both cart slots would fail in this regard at exactly the same time. Also, given that it's only present with triggered sound effects and not music it makes me think it's at the audio processing level. I do have a spare z80 I could throw in. The YM naturally, I don't.

Both slots connect to the same Z80 and YM.

 

[malignantpoodle]

Wow, my post deleted? That's interesting.

Hmm... anyway, continuity is solid.

 

[Xian Xi]

MV2 or MV2F?

 

[Tyranix95]

My post is missing too.

 

[Tyranix95]

MV2 or MV2F?

...MV-2F board.....

 

[Xian Xi]

Haha, ya I saw that after I posted it.

Ok well since it's an MV2F, the popping exists on both headphones and jamma sound and you said continuity is 100% between YM2610, Z80 and cart slots. You also said you recapped the board but which caps did you replace exactly?

Since it affects both sound outputs it could most likely be a 4.7uf cap on the second 4558 chip or even the 4.7uf caps coming from the YM2610 (pin 27). Try replacing those.

 

[malignantpoodle]

Aye, I've replaced every electrolytic cap on the entire board. All of them.