Strange 2 Slot sound problems: broken chip?

[[OCEAN]]

Hi,

I've got some strange sound problems with a 2 slot board (MV-2F) and I haven't got a clue what may be causing them.

The main problem is that it seems there are some sound samples missing in most of the games, like if the music was incomplete (when compared with the same carts played on my 1 slot). Also the music sounds cracky, with "pops" going on all the time.

Before asking I've tried the following with no luck: Cleaning thoroughly the cart slots, the jamma connector and the board itself, checking if there were some pins in contact, checking for any blown component and measuring if there were any broken resistors.
The sound test seems fine on both channels and there are the same problems when listened through the headphone jacks.
Also, I tried the board on a raijin supergun and on a cab, to discard any problems related to the PSU, the speakers, or the jamma harness.

I recorded some samples from MOTW and SS4 directly through the headphone jacks, to illustrate what I'm trying to explain, if someone is willing to check it out:
http://www.megaupload.com/es/?d=ES7T0M15
(It's a 2.2MB zip with 3 wavs, sorry for the crappy megaupload link)

I'm starting to think this may be a problem related with one of the sound chips, but I haven't got a clue on how to start investigating in that direction.
Anyone has any idea what may be the problem here? or any other thing I could try? Any help will be greatly appreciated.

Thanks in advance,

[OCEAN]

 

[channelmaniac]

Without you having an audio signal generator and an oscilloscope all I can suggest as a first course of action would be to shotgun all the electrolytic caps in the sound section of the board.

RJ

 

[[OCEAN]]

Without you having an audio signal generator and an oscilloscope all I can suggest as a first course of action would be to shotgun all the electrolytic caps in the sound section of the board.

RJ

Thanks for the suggestion, but what do you mean exactly by "shotgunning" the caps?

[OCEAN]

 

[channelmaniac]

Replacing all of them in the audio section of the board.

 

[[OCEAN]]

I guess you are talking about all the cylindrical ones in this part of the board?

Just want to be sure before I start to change components,
thanks again

[OCEAN]

 

[channelmaniac]

Yup...

They have capacitance rating (in uf) and voltage ratings on them...

Typically they are rated at 85 degrees C, but you can put 105 degree ones in if you want - they are more expensive. I prefer the 105 for monitors and power supplies since they run hot, but the board can use the cheaper ones.

Oh, and they are polarized. Make SURE you put them in correctly.

RJ

 

[[OCEAN]]

Well, finally I had some time today to buy new electrolytic caps and replace all the old ones from the board (and also remember that I'm not that good at desoldering ).

Unfortunately, when I tested it nothing had improved and the sound remains the same way (cracky and missing some samples).

Is there any other thing I could try? Or should I start looking for a new motherboard?

Thanks,

[OCEAN]

 

[Xian Xi]

post a close up pic of the bottom of the board where the sound section is, it could be something as small as a broken trace.