Need help with a portable.

[jeffslot]

Hi guys,

I pulled the jamma board of of my project pictured below:



I love the way that this project came out, but there are a couple of upgrades I want to perform on it (make it smaller, and remove the 12v dependency).

Can you tell me on the board pictured below, where is the audio amp?



Is it in the below region?



Would this work similar to a mv1-c where you need to remove the audio amp & then cut the lines on the back? If so where on the back would I find the lines I need to cut?







Also provided I can find the right lines to cut, where on the parts side would I be able to pick up the left/right audio lines?

I'm asking for generic & specific help on this, because I want to perform this mod on this board and also on a upcoming mv1-b project that I'm working on. Any help will be greatlly appreciated.

I definitely don't claim to know a lot of stuff, but I can do some stuff, so please be patient and understanding with me. Thanks so much.

Someone on another board, pointed me at the following data sheet, but it is a bit over my head..

http://www.st.com/stonline/products/lit ... s/1449.pdf

Thanks

Jeff

[arfink]

Not quite sure where to "chop" so to speak, but that big thing with the heat sync attached to it is almost certainly the main audio amp, it looks the same as on my Neo Geo board. BTW, my Neo is an MV-1FZ. You *should* be able to just unsolder that one part and tap the unamplified signal from there. Only problem is finding where your board mixes the stereo into mono for that amp. You may need to follow some leads backwards from that main amp until you find what you are looking for. You will know what you want because there will be two traces being joined, and before the join will be individual filtering circuits, which if you trace backwards from there will go into separate pins of the audio chip(s).

You can use an oscilloscope if you have one to trace the signals back to make sure before you chop anything up. That's what I had to do on mine.

Good luck!

BTW, I loved your first portable, I hope your next will be even more awesome!

[jeffslot]

Arfink,

Thanks for giving me that info. The only bad thing is that I don't own an
oscilloscope (or know how to use one), also I'm not too sure what individual filtering circuits might look like, but I'll definitely give the board a close look & see if I can figure anything out (doubtfull, but I'll try). Thanks

Jeff

[RezCrimson]

that's a bad@$$ portable dude! Keep up the good work.

I especially like the ps analog

[arfink]

Well, if you don't have the 'scope, here are some tips which should help.

First off, the filter circuit usually has several larger capacitors in it. The caps filter out noise. One thing, you won't need to bypass those circuits, they are GOOD, and you need them there. They also don't use the 12v. Here is the thing, I'm thinking your board doesn't even have stereo, so it might be just fine to pull the amp and simply pull your unamplified signal from there.

If you want to trace backwards and you want to make sure you still have an audio signal on the trace, you could take a little peice of sandpaper or a small file and carefully scrape the plastic top coating off the trace to expose it, and then chop up and old pair of headphones and touch one wire to the exposed trace and the other one to ground. Be careful not to damage the trace! Then, after you hook up your headphone wire, listen to see if you are getting sound. If you don't hear anything or you are hearing noise you've probably got the wrong trace. If you short the wrong thing to ground and the system starts acting up, you can probably just reset the machine and it should go back to normal. Old arcade board are more robust than you think, you just need some common sense.

Good luck, keep me posted and I'll see what I can do to help.

[jeffslot]

arfink,

Thanks for helping me out. It will take a bit for me to get everything back to the point where I'm ready to test for sound with that headphone method, but I'll try and isolate any areas that seem to have the large caps near the audio amp. Also does it make a difference if the board isn't old, but new?

Thanks.
jeff

[arfink]

Hmm, not what you mention it, the board does have a new-ish date printed on it. Well, I don't think it should make too much difference, that was really just a generalization, since in my experience JAMMA board are built very tough.

[IIIUUU]

Now that is a lot of brass air fittings http://www.liangdianup.com/subpages/airfitting_1.htm there is just about every type
of air fitting that you could want. Wholesale prices too. I guess these could be used as small water pipe fitting also. I
used some of the parts to make my babington wvo bu

[Kyo]

Great, now even the robots are bumping