Got a weird one here fellas.. Dreamcast MGCD wiring for a JAMMA edge connector...

HornheaDD

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So, this "JAMMA" conversion of a Dreamcast isn't really JAMMA. Its got a weird wiring diagram where it wires all of the action buttons to the JAMMA edge connector. So Pins 27/28 on each side which are usually ground (as is my understanding). Because of this, if you hook it up to a standard harness, the thing will start up just fine, but will NOT work with any controls. Controls will be dead to the world.

Ive looked around and some people say to clip/disconnect 27/28 on each side of the harness, and this will fix it. That is not the case. Then someone on KLOV said this:
In order to get the controls on the arcade cab to work you need to cut the last two connectors (27 & 28 on both sides in the JAMMA Pinout Diagram above) and splice them into the power ground (1 & 2 in the JAMMA Diagram above). If you don't connect them to ground, none of your controls will work. This is different from what has been posted elsewhere that said you can just cut and cap off the wires or just lift the pins.

So, I've tried creating an adapter and the lifted pins solution does not work. I tried what I *assume* to be routing those connectors to the power grounds.. as far as I know I did it correctly, but it's still not working.


This is the MGCD pinout.
mgcd_zps19c74af1.gif


JAMMA Pinout:
jamma_zpsb70da3d9.gif



This is what I was able to get from the quote I posted:

EOXhHpB.jpg



Make fun of me if you want to, but that's the only thing I can imagine he meant to do, and naturally its not working still. System boots up nicely, and will work with a Dreamcast controller plugged in, but cab controls do not respond at all. Any ideas? The guy that claims he got it to work by leaving the pins disconnected has a post here: http://arcadefever.blogspot.com/2010/05/hacking-mgcd-part-1.html

but he hasnt posted there since 2018 so I doubt he'd respond to anything.
 

awbacon

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So, this "JAMMA" conversion of a Dreamcast isn't really JAMMA. Its got a weird wiring diagram where it wires all of the action buttons to the JAMMA edge connector. So Pins 27/28 on each side which are usually ground (as is my understanding). Because of this, if you hook it up to a standard harness, the thing will start up just fine, but will NOT work with any controls. Controls will be dead to the world.

Ive looked around and some people say to clip/disconnect 27/28 on each side of the harness, and this will fix it. That is not the case. Then someone on KLOV said this:


So, I've tried creating an adapter and the lifted pins solution does not work. I tried what I *assume* to be routing those connectors to the power grounds.. as far as I know I did it correctly, but it's still not working.


This is the MGCD pinout.
mgcd_zps19c74af1.gif


JAMMA Pinout:
jamma_zpsb70da3d9.gif



This is what I was able to get from the quote I posted:

EOXhHpB.jpg



Make fun of me if you want to, but that's the only thing I can imagine he meant to do, and naturally its not working still. System boots up nicely, and will work with a Dreamcast controller plugged in, but cab controls do not respond at all. Any ideas? The guy that claims he got it to work by leaving the pins disconnected has a post here: http://arcadefever.blogspot.com/2010/05/hacking-mgcd-part-1.html

but he hasnt posted there since 2018 so I doubt he'd respond to anything.
Yeah that makes no sense lol (not your thoughts. The cutting part)

this is an instance where it’s better to solve the problem outside of the harness. You say the Dreamcast controller ports work and I assume the Dreamcast is in the cab so...

pad hack it. Just grab a cheap Dreamcast controller and solder your stick into the D pad and buttons into the button pads.

eliminate the harness entirely and it’ll function exactly as needed.

at least that’s what I’d do
 

HornheaDD

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Well thats the thing, the whole point of this little doodad is that it's a "Drop in" thing. It was intended as a cheap NAOMI replacement. It's not a hack or like a JAMMAfied Genesis.

The board has some kind of software that was 'aware' of certain splash screens and whatnot, and it would hide them, and lock the controls until it was coined up. So basically a cheapskate ArcadeOp could buy a DC, and say Marvel Vs Capcom 2, slap the disc in the drive, fiddle with the dip switches to "tell" the board that MvsC2 was in there -and players were none the wiser. It only worked with about 100 games in Japan/Korea, but I was able to modify it to remove an overlay (it was time for coin, etc) and with an ODE in it, it bypasses the dipswitch thing.

Check out this vid, it's in spanish but skip to about 1:30 and you'll see the set up. It's actually kinda cool, but not immediately JAMMA compliant - even though it was designed to be a drop in solution.


I found a *couple* of other posts on line about it, and one dude is kinda helping me out but I need to wait for my extension harness to show up. Im not about to hack up my MVS' harness.
 

awbacon

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Well thats the thing, the whole point of this little doodad is that it's a "Drop in" thing. It was intended as a cheap NAOMI replacement. It's not a hack or like a JAMMAfied Genesis.

The board has some kind of software that was 'aware' of certain splash screens and whatnot, and it would hide them, and lock the controls until it was coined up. So basically a cheapskate ArcadeOp could buy a DC, and say Marvel Vs Capcom 2, slap the disc in the drive, fiddle with the dip switches to "tell" the board that MvsC2 was in there -and players were none the wiser. It only worked with about 100 games in Japan/Korea, but I was able to modify it to remove an overlay (it was time for coin, etc) and with an ODE in it, it bypasses the dipswitch thing.

Check out this vid, it's in spanish but skip to about 1:30 and you'll see the set up. It's actually kinda cool, but not immediately JAMMA compliant - even though it was designed to be a drop in solution.


I found a *couple* of other posts on line about it, and one dude is kinda helping me out but I need to wait for my extension harness to show up. Im not about to hack up my MVS' harness.
What a weird little device. Best of luck with it. The whole “ground to power ground” thing is strange. But good luck with it!
 

Lemony Vengeance

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Gotta make a passthrough adapter for it.

or buy a JNX atlas and modify pin 28 to account for “button 7”
 

HornheaDD

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I've tried a passthrough, removing 27/28 on each side and it didn't work. I also have an Atlas, and tried the jumpers on both settings :(
 

awbacon

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I've tried a passthrough, removing 27/28 on each side and it didn't work. I also have an Atlas, and tried the jumpers on both settings :(
I mean did you ever see it working? May want to consider that there is something else wrong internally?
 

HornheaDD

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Definitely considered that. That's why Im trying cheaper troubleshooting. An extension harness was like 15 bucks on Amazon, I got a fingerboard and edge connector to make a passthrough, etc. I dont know how to troubleshoot PCB components. It's entirely possible that it's busted - BUT... these devices are known for not being JAMMA compliant out of the box and needing modification to the harness. So as of right now, it's still a 50/50 chance its working lol
 

HornheaDD

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So here's the thing. @Lemony Vengeance

I made a passthrough board the other day. Take a look, it's shoddy work but the joints are solid and if/when I can get it to work I'll clean it up and make it less shitty looking. Now from what I was told by the KLOV guy, he said that 27/28 on each side need to be bridged into A1/B2, right. So what I did is I bridged the pads from 27/28, and then ran a lead from there to A1 and B2 respectfully. He told me that I had it wired wrong and that I needed to bridge between the two lifted pins and bridging them to A1/B2 on each side. This didn't work either.

Considering where the signal is coming from on the Harness, isn't what I have soldered here sound? The signal/power/etc is coming from the JAMMA edge connector, into the fingerboard, and the red wire is bridging those two pins to A1/B2.

I figure this would be the same as ripping the ground cables from the harness and bridging those two to A1/B2. I'm confused on this, and I'm concerned that when I do this with the JAMMA extension I got, it's still not gonna work.

 

HornheaDD

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Got an update on this thing.

I ended up buying a 2nd MGCD for cheap from a dude in Mexico. It came in today - and it works. I used an Atlas adapter I got from JNX and everything works fine. The buttons are swapped a bit, but I think that's just the design of the board, not a Dreamcast, Cab, or Atlas' fault. I guess the previous one I got was possibly messed up. I'm having it looked at by JNX to see if there's anything that can be repaired on it, but who knows.

With a working one, having a Dreamcast in the cab is pretty sweet, especially now that I can even play all of the Atomiswave games. Shit why'd this thing have to show up mid-week lol.
 

awbacon

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Got an update on this thing.

I ended up buying a 2nd MGCD for cheap from a dude in Mexico. It came in today - and it works. I used an Atlas adapter I got from JNX and everything works fine. The buttons are swapped a bit, but I think that's just the design of the board, not a Dreamcast, Cab, or Atlas' fault. I guess the previous one I got was possibly messed up. I'm having it looked at by JNX to see if there's anything that can be repaired on it, but who knows.

With a working one, having a Dreamcast in the cab is pretty sweet, especially now that I can even play all of the Atomiswave games. Shit why'd this thing have to show up mid-week lol.
glad you got a working one. and yes cool packages always show up mid week when you have zero time to play with the shit in the box. It's basically the law
 

SignOfZeta

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Since there is no “JAMMA” in China there is no legal compulsion to put the kicks on a separate harness. They put them on the edge at unused pins. This is so common now that there are super guns that support it.

Perhaps someone plugged this into a cab with something other than switches on those pins and fried something or perhaps it was born dead. I for sure have been in a situation where I’m trouble shooting some knockoff bullshit I got from someone and eventually found a bad solder joint or whatever that proved it never actually worked for anyone. :)
 

Gremlin

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Glad you figured it out! What a ball-ache, it's the worst when it turns out it never worked at all. I didn't even know this existed before this thread, so thanks for that!
 

HornheaDD

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For sure. Im hoping maybe its just something I missed on the other one, or if it's fixable. If it is, I'd like to trick out another DC (already got a spare) and sell it. Might bring in a few pennies.
 
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