What is it that actually goes wrong when you plug a JAMMA system into a stereo harness?

[protheus]

Maybe while I'm at it I can also post about a problem I'm still actually having. There's a bunch of vague stuff about how you'll burn something out doing this, but nobody is ever specific. What is it that overheats when you hook up a JAMMA board to a non-JAMMA MVS cab, and why? Does anyone know?

I ask because I have a bit of a problem figuring out whether my MVS is actually generating stereo. First off, when it's hooked up in the usual stereo MVS arrangement, it does seem to produce sound on both speakers. Does this mean it's stereo? Well, I thought so, but I also can't for the life of me figure out why I'd burn the board out if it weren't, so it occurs to me that I may not know everything about the hardware on the other side of that card edge. So I'd just check the internet to be sure, but my MVS is apparently a bootleg -- a quite interesting one that nobody seems to know about so far -- and there's really no information on _what_ it ought to be doing.

I guess in order, what's actually the problem with a mono board in a stereo configuration? Does anyone know, in particular, precisely what is supposed to get too hot and cook itself in these configurations? If I wire things up in stereo and sound comes through both speakers, is that really proof that there's stereo output?

Chris

 

[Psygnosis8]

I use a 2 slot and plug a 3.5mm to rca cable in and plug that directly into a 2.1 stereo amp. Never had a problem.

If it's running in stereo that should be obvious while you play. You should probably just get a real board.

 

[Westcb]

Maybe while I'm at it I can also post about a problem I'm still actually having. There's a bunch of vague stuff about how you'll burn something out doing this, but nobody is ever specific. What is it that overheats when you hook up a JAMMA board to a non-JAMMA MVS cab, and why? Does anyone know?



I ask because I have a bit of a problem figuring out whether my MVS is actually generating stereo. First off, when it's hooked up in the usual stereo MVS arrangement, it does seem to produce sound on both speakers. Does this mean it's stereo? Well, I thought so, but I also can't for the life of me figure out why I'd burn the board out if it weren't, so it occurs to me that I may not know everything about the hardware on the other side of that card edge. So I'd just check the internet to be sure, but my MVS is apparently a bootleg -- a quite interesting one that nobody seems to know about so far -- and there's really no information on _what_ it ought to be doing.



I guess in order, what's actually the problem with a mono board in a stereo configuration? Does anyone know, in particular, precisely what is supposed to get too hot and cook itself in these configurations? If I wire things up in stereo and sound comes through both speakers, is that really proof that there's stereo output?



Chris

Taken from me just typing your silly question in Google:

JAMMA boards require an adapter to run in an MVS cabinet. The MVS cabinet is wired for stereo audio and the differences in the cabling causes damage to the audio amplifier IC chip on the JAMMA board.
The damage is usually not immediate but will occur if the board is run for a long while. The difference in wiring results in the audio amplifier IC chip getting hot enough to blister fingers and fail.
To avoid this, use a JAMMA to MVS adapter such as this which takes care of the audio wiring, test button, and other wiring differences between the JAMMA and MVS wiring.

There's your answer, don't argue just get an adapter :-)

 

[protheus]

I've already typed the question into Google, as you may imagine, but that doesn't really answer my question. Which thing on the board is the audio amp -- you may have noticed there are a number of ICS, and a few of them apparently related to audio -- and why is it cooked when you connect the speaker negative and the common ground through a (presumably dead, but who knows if this is true) speaker? That's the only related difference in wiring, so what, in particular, is wrong with doing it? Do they use different amps on the stereo boards? I'm looking for specifics, such as may be available, so I can compare what happens in the usual configuration to this rather weird case. I also don't need an adapter. I'll just rewire the audio output if it needs it, but I want to be sure it needs it before I take what may actually be a stereo signal and cripple it by slicing half of it away.

Chris

 

[protheus]

I use a 2 slot and plug a 3.5mm to rca cable in and plug that directly into a 2.1 stereo amp. Never had a problem.

If it's running in stereo that should be obvious while you play. You should probably just get a real board.

Err, aren't all the two-slot boards stereo ones anyway, though? Anyway, perhaps I should get a real board -- and I have an only slightly broken actually mono MV1-FZ on the way. I'll probably patch it up and get it going as well, but I'd still like to figure out whether or not this one is actually making stereo output.

 

[Westcb]

I've already typed the question into Google, as you may imagine, but that doesn't really answer my question. Which thing on the board is the audio amp -- you may have noticed there are a number of ICS, and a few of them apparently related to audio -- and why is it cooked when you connect the speaker negative and the common ground through a (presumably dead, but who knows if this is true) speaker? That's the only related difference in wiring, so what, in particular, is wrong with doing it? Do they use different amps on the stereo boards? I'm looking for specifics, such as may be available, so I can compare what happens in the usual configuration to this rather weird case. I also don't need an adapter. I'll just rewire the audio output if it needs it, but I want to be sure it needs it before I take what may actually be a stereo signal and cripple it by slicing half of it away.

Chris

I did answer your question, you asked what is it that burns up and why. The audio IC, it burns up because the cabling is wrong. That's the question answered. No one will be able to tell you the location on your board of the amp as you said yours is special and undocumented.... Only you can find it bud unless you do something for yourself like post a picture of it???
And yes you need an adapter, because you should never neuter the original wiring in a MVS cab to play Jamma when you can just get an adapter to do so, otherwise why have a MVS cab? And can you seriously not tell the difference of stereo and mono wiring? Just poke your head in the cab and follow the cables. If you see one audio wire spliced to two speakers it's mono, if you see two sets yours stereo. I'm assuming your MVS cab came with that board or did you just buy a separate bootleg MVS board yourself?if sound is not burned out by now then it's probably mvs configured if that board has been in there for any length of time.

 

[Psygnosis8]

Err, aren't all the two-slot boards stereo ones anyway, though? Anyway, perhaps I should get a real board -- and I have an only slightly broken actually mono MV1-FZ on the way. I'll probably patch it up and get it going as well, but I'd still like to figure out whether or not this one is actually making stereo output.

Sorry, I didn't clarify that I'm using a candy cab.

And you can find the audio amp on a board easily. It usually has a huge heat sink and gets real hot when you play. It will have a bunch of capacitors around it as well.

 

[protheus]

I did answer your question, you asked what is it that burns up and why. The audio IC, it burns up because the cabling is wrong. That's the question answered. No one will be able to tell you the location on your board of the amp as you said yours is special and undocumented.... Only you can find it bud unless you do something for yourself like post a picture of it???
And yes you need an adapter, because you should never neuter the original wiring in a MVS cab to play Jamma when you can just get an adapter to do so, otherwise why have a MVS cab? And can you seriously not tell the difference of stereo and mono wiring? Just poke your head in the cab and follow the cables. If you see one audio wire spliced to two speakers it's mono, if you see two sets yours stereo. I'm assuming your MVS cab came with that board or did you just buy a separate bootleg MVS board yourself?if sound is not burned out by now then it's probably mvs configured if that board has been in there for any length of time.

I should be clear, I was hoping for an answer that might actually help figure the cause of the problem out rather than just a generic one that assumes I have no clue what I'm doing and should throw some money at a problem that may not exist on my board. If you'd read my previous post, you would have found that I clearly and precisely stated the difference between stereo and mono wiring, so I honestly have no idea what you're taking about there. Basically I'm hoping somebody who is a huge Neo Geo fan is also an electrical engineer who can tell me why the amps cook themselves in that configuration when it seems to me that they should not. "Because the wiring is wrong" begs the question and gets me no closer to really answering it. I thought it may be a longshot to find a thorough treatment of this problem, but you never know. Next best option is to find somebody who knows which amps are on which MVS boards and dig out the datasheets to find the answers, but even if I pull my board and start typing numbers into Google for the things that look like amps, I'd love to be able to compare it to a real thing, or three. If you know of anywhere that has that kind of information, I'd love to hear about it.

Also there's no cab. I have a Tekken cab, but it was gutted before I managed to get it and has no wiring and won't be used for this board (or probably my new one) for now. The whole thing is in a custom box that I built myself, which can be rewired easily in either configuration with no damage. I won't be butchering an SNK harness of any sort for this. I'm rather opposed to that kind of thing. The board was bare when I got it. It has been played briefly in both stereo and mono configurations since then, and nothing on the board seems to heat up much either way. I just want to be sure.

Chris

 

[protheus]

Sorry, I didn't clarify that I'm using a candy cab.

And you can find the audio amp on a board easily. It usually has a huge heat sink and gets real hot when you play. It will have a bunch of capacitors around it as well.

I did suspect that it was that one. Thanks. I may pull out a datasheet on it and see how it looks. Maybe I can make some sense of the part of the board between it and the card edge. Good news is that it doesn't seem to get hot at all. Bad news is that I think it has too few pins to be a stereo amp, so even if it doesn't melt itself, it may not help anything.

 

[Xian Xi]

Impedance of the amp needs to match the speaker(s). In the case of JAMMA to MVS(mono to stereo), JAMMA and MVS are the same impedance when the stereo setup is wired in series (+- -- -+) via an adapter but wired in stereo in parallel (+- +-) it's a lower impedance and will pull more power than the amp can provide comfortably which causes it to overheat and ultimately fail. Depending on the specs of the JAMMA board's amp, impedance of the cabs speakers and the wiring configuration, you can blow the amp in seconds all the way up to a week. It just depends.

 

[protheus]

Impedance of the amp needs to match the speaker(s). In the case of JAMMA to MVS(mono to stereo), JAMMA and MVS are the same impedance when the stereo setup is wired in series (+- -- -+) via an adapter but wired in stereo in parallel (+- +-) it's a lower impedance and will pull more power than the amp can provide comfortably which causes it to overheat and ultimately fail. Depending on the specs of the JAMMA board's amp, impedance of the cabs speakers and the wiring configuration, you can blow the amp in seconds all the way up to a week. It just depends.

I didn't even think of that (well, obviously)... thanks. That was the answer I was looking for.

Chris

 

[protheus]

Impedance of the amp needs to match the speaker(s). In the case of JAMMA to MVS(mono to stereo), JAMMA and MVS are the same impedance when the stereo setup is wired in series (+- -- -+) via an adapter but wired in stereo in parallel (+- +-) it's a lower impedance and will pull more power than the amp can provide comfortably which causes it to overheat and ultimately fail. Depending on the specs of the JAMMA board's amp, impedance of the cabs speakers and the wiring configuration, you can blow the amp in seconds all the way up to a week. It just depends.

Err, do you also know whether -- wired in parallel -- there will still be sound on both speakers in general? That part confuses me too.

 

[Xian Xi]

Err, do you also know whether -- wired in parallel -- there will still be sound on both speakers in general? That part confuses me too.

From JAMMA mono to parallel stereo? You only would wire it to one speaker, you could split the signals but would have to use higher ohm speakers so you don't damage the audio amp. So if the amp is rated for 8ohms, you'd use 2 x 16 ohm speakers to keep it as 8 ohm impedance. Just remember that the lower the impedance on a speaker, the more power it pulls.

 

[protheus]

From JAMMA mono to parallel stereo? You only would wire it to one speaker, you could split the signals but would have to use higher ohm speakers so you don't damage the audio amp. So if the amp is rated for 8ohms, you'd use 2 x 16 ohm speakers to keep it as 8 ohm impedance. Just remember that the lower the impedance on a speaker, the more power it pulls.

Right. What I meant was, if a mono amp were wired improperly in the way that the stereo ones are wired, aside from burning out the amp, would it generate sound on both speakers, or would one channel be quiet? I ask because my board is as likely as any to have a mono amp, though I haven't verified this yet, and when I had it wired as if it were stereo briefly, it did make noise on both speakers.


Chris

 

[Westcb]

Right. What I meant was, if a mono amp were wired improperly in the way that the stereo ones are wired, aside from burning out the amp, would it generate sound on both speakers, or would one channel be quiet? I ask because my board is as likely as any to have a mono amp, though I haven't verified this yet, and when I had it wired as if it were stereo briefly, it did make noise on both speakers.





Chris

You still haven't posted a picture of the board.....

Also... This will make things go quicker

What happens when you ground pin M on solder side? Does it activate test? If so its MVS wired, if not its Jamma and will be mono. Or am I still not understanding what you need help with. If however you have it wired now puts out good clean sound just play it and listen, shouldn't be too hard to tell if something is outputting stereo or mono sound, it's night and day different unless you are using some old soup cans for speakers.

 

[Xian Xi]

Right. What I meant was, if a mono amp were wired improperly in the way that the stereo ones are wired, aside from burning out the amp, would it generate sound on both speakers, or would one channel be quiet? I ask because my board is as likely as any to have a mono amp, though I haven't verified this yet, and when I had it wired as if it were stereo briefly, it did make noise on both speakers.


Chris

Like I said, it depends on how the speakers are wired. If they are wired in series then sound should be on both but wired in parallel it will be only on one side.

 

[protheus]

Like I said, it depends on how the speakers are wired. If they are wired in series then sound should be on both but wired in parallel it will be only on one side.

This is getting all the more interesting. They were parallel -- as in, positive pole of each speaker to one of the lines that would be speaker +/- on a JAMMA edge -- and they did both make noise.

Westcb, I've left the board at work, but did mean to photograph the thing eventually. I'll take pictures next week and throw them out here. I'll also test connecting pin M to ground.

Chris

 

[protheus]

Not much time for this today, but I did pop the cover off and get a photo of the board.




Chris

 

[Westcb]

Not much time for this today, but I did pop the cover off and get a photo of the board.





View attachment 38672



Chris

I would bet you dollars to donuts that's Jamma and you have mono sound. Also just curious, are you the one who created that abomination :-) I thought you mentioned this was in a tekken cab but it looks like someone is trying to consolize it in a wood box.

 

[protheus]

I would bet you dollars to donuts that's Jamma and you have mono sound. Also just curious, are you the one who created that abomination :-) I thought you mentioned this was in a tekken cab but it looks like someone is trying to consolize it in a wood box.

Ha. No, I have an old Tekken cab but am not using it at the moment. Anyway, if you mean the board, of course not, err, but if you mean the box, yes I made it, along with the joystick driver circuits and the video encoder. The power supply is from an old rack-mount Pentium III that I dug out of a pile of trash, the power switch was a low-voltage AC illuminated switch that I hacked up to run off of the 5v rail here, and most of the fittings are from the hardware store.

It's unconventional, I guess. I also sliced out the SNK logo on top with a Dremel. I should be able to use the same box to run my MV1FZ that I just picked up. Size of this one is slightly larger, but comparable.



Chris

 

[Xian Xi]

That board should be mono since it's JAMMA but it's hard to say since it's a bootleg MVS board and I've never seen one in person but if it's setup like the boards it's copying then it's JAMMA mono.

 

[protheus]

You still haven't posted a picture of the board.....

Also... This will make things go quicker

What happens when you ground pin M on solder side? Does it activate test? If so its MVS wired, if not its Jamma and will be mono. Or am I still not understanding what you need help with. If however you have it wired now puts out good clean sound just play it and listen, shouldn't be too hard to tell if something is outputting stereo or mono sound, it's night and day different unless you are using some old soup cans for speakers.

To finally answer your question, pin M does nothing. Grounding the JAMMA "service" lead seems to cause a screen refresh but nothing interesting. The JAMMA test one permits me to set soft dips and so on.

Chris

 

[protheus]

That board should be mono since it's JAMMA but it's hard to say since it's a bootleg MVS board and I've never seen one in person but if it's setup like the boards it's copying then it's JAMMA mono.

Yeah, at this point I may just keep the box wired for mono since it's the safe bet, and since I'd like to also make it work for the MV1FZ, which is definitely supposed to be mono. Seems like there's not a whole lot missing in this thing between stereo wiring on two speakers and mono wiring split to two speakers anyway, so I suppose I may as well play it safe unless I decide to pop the heat sink off of the amplifier (which is in a somewhat inconvenient place) and check it.

 

[mikejmoffitt]

PM sent, I'm very interested in your bootleg board.