How to convert a MVS board into Jamma

As is known MVS multi-slot boards aren't fully Jamma compliant. The most notable differences are:

- stereo on the edge connector (MVS) vs mono (Jamma)
- test pin at Jamma M (MVS) vs test pin at Jamma 15 (Jamma)

Then we have the select button (jamma 26/d) but this isn't as big a difference because it can easily be added and even some jamma cabs (Egret II, AWSD) have Jamma 26/d wired to the 5th button on the control panel, so if you have a 6-button CP it may be a good idea to wire the 5th button to both the kick harness and jamma 26/d.
It's worth noting that the Jammaboards MVS-to-Jamma adapter "adapts the NeoGeo MVS ‘Game Select’ Up/Down feature to work with the existing JAMMA cabinets Player 1 & 2 first shooter buttons, eliminating the need to install new selection buttons". However, this does not take into account the fact that with the Universe Bios set to console mode select works as pause so every time you press A it will pause the game, making it unplayable.

Anyway, why would someone want to convert a MVS multi-slot (a MV2F in this case) into a Jamma board? Well, to use it in a Jamma cab without having to buy an external adapter. Consolized units in particular would benefit from this conversion: we all have seen those consolized MVS sale ads where the seller/builder proudly claims that the Jamma (?) connector was not sacrificed in the process and the unit can still be used in a cab. Yeah but not in a Jamma cab and there is little doubt that if a CMVS owner is going to put his CMVS in a cab it will be a Jamma cab.

Let's start with the stereo-to-mono mod. The power amplifier on multi-slot boards is a Hitachi HA13001. As the datasheet shows, this amp can be set to either stereo or mono with only a few alterations:



1) Desolder the components shown in the pics below: three electrolytic caps (2x 100uF, 1x 4.7uF) and two 100 ohm resistors:






2) The new components that need to be installed are:


(the 100uF caps are going to ba replaced only because the old ones don't have long enough leads)

3) Bend the new components like this (and solder the 0.022uF polyester cap to the 1Kohm resistor):



4) Solder the 100uF caps so that the negative leads touch each other:



5) Solder the 1Kohm resistor + 0.022uF cap so that one side goes where the + lead of the desoldered 4.7uF cap was and the other side touches the negative leads of the 100uF electrolytic caps:



6) Solder the 1Kohm resistors where the 100ohm ones were:



7) Solder a piece of a resistor lead across pin 1 and 4 of the amplifier and bridge together the newly soldered 1Kohm resistors:





Now let's move the test input pin from Jamma M to Jamma 15.

1) Point 1 is test and goes through 2 and 3 (far right) to Jamma M, while point 4 goes through 5 to Jamma 15:



2) With a sharp blade (Stanley knife, X-acto knife, etc.) cut and lift the trace that goes from 2 to 3 until it comes off:




3) Let's move to the parts side of the board. Cut and lift the trace that goes from 4 to 5 until it comes off:



4) With a small flat head screwdriver scrape off the solder mask around the vias marked 2 and 5 on both sides of the board so you can solder to them.

5) Take a short piece of uninsulated solid-core wire (the type used for wire-wrapping) and solder it across vias 2 and 5:



6) Check with the multimeter that you have continuity across point 1 and Jamma 15.

BUMP for an awesome guide!

I do have a noobie question to throw in here... if setting up to also play some jamma on here (jamma to mvs adapter) where do you pull the 5V from? Or is this not necessary?

Great work MKL, this should definitely be stickied, its a valuable addition to the site.

Any chance you'd be willing to do a guide on how to modify a board so that it outputs unamplified audio?

xiao_haozi said:

BUMP for an awesome guide!

I do have a noobie question to throw in here... if setting up to also play some jamma on here (jamma to mvs adapter) where do you pull the 5V from? Or is this not necessary?

Click to expand...

I'm not sure what you mean. If you mean where to pull -5v from in a MVS cab when using jamma boards that need that voltage (in addition to 5v and 12v) to work properly, it depends on whether the MVS cab PSU can output -5v and the -5v pins on the MVS edge connector are wired or not. I think the stock PSU in US MVS cabs (the big reds) does output -5v but the wires on the MVS edge connector are missing. I think www.hardmvs.com has something on this:

http://www.hardmvs.com/html/neg5volt.htm

If you meant something else, please try to explain yourself better.

Hewitson said:

Great work MKL, this should definitely be stickied, its a valuable addition to the site.

Any chance you'd be willing to do a guide on how to modify a board so that it outputs unamplified audio?

Click to expand...

If the headphones out is too much amplification for your purposes, then you could try tapping audio from any of the points marked A, B, C, G (they're all the same) for the Right channel and points D, E, F, H (also all the same) for the Left channel. Note that points marked I are the unamplified mono output on Jamma 11 and that's *very* quiet. ABCG and DEFH will also be quiet though. I think the headphones out is better.

MKL, this isn't directly related but close to.

I hope you can answer, if not I am sorry for posting and wasting your time .

I have an AWSD and still use that stereo adaptor harness you made me all that time ago. Now, I use an MVS->JAMMA adaptor card also. I am pretty sure my AWSD is wired for 5 buttons already as you mentioned before. however, am I right in thinking I could just actually wire select and D up to the jamma wires instead of wiring them from the adaptor card?

at present I have your stereo harness and another harness (just for select + D) wired to the card, if I realised I could wire select+d to the cab harness, and just use the stereo harness off the adaptor card, I'd rather wire it up this way instead.

I guess some investigation is needed

thanks

(ah, but then I just realised I'd still be using the mvs->jamma adaptor card, and that might change the pinout so it is just 3button jamma and therefore I wouldn't be able to wire select/d up anyway)

confusing!

D'oh! I just remembered my jamma extension harness is wired for plain jamma, so it doesn't even matter if my cab would support it, because the extension wouldn't

sorry to waste your time

kernow said:

I am pretty sure my AWSD is wired for 5 buttons already as you mentioned before. however, am I right in thinking I could just actually wire select and D up to the jamma wires instead of wiring them from the adaptor card?

Click to expand...

I don't know the details of the MVS-to-Jamma adapter, all I know is that if you put a MVS board in an AWSD cab with a 6-button CP the MVS buttons will be mapped like this:



You can check that yourself by plugging a multislot (with volume off) directly into the jamma connector.

But I think most if not all people disconnect the original wires from the bottom row buttons to fit the kick harness so the lose the connections with the 4th and 5th jamma buttons.

yeah, thats exactly what I've done, they aren't wired any more but I'd just test by sticking a button on the end.

Thing is, my extension harness is wired for 3 buttons only so I know D doesn't work when using it, and I need the harness as the AWSD one is super short and I couldn't use the four slot else.

I guess I could use a straight through extension harness with all pins wired, but I have this one already so eh.


Thanks for your quick reply though! cheers.

Well if the wires originally connected to the bottom row (those coming from the CP connectors J and K) are disconnected, even a fully wired jamma extension wouldn't get them to work. I suggest you crimp the kick harness wires in parallel with the original wires (two wires on the same quick-disconnect) and add the 4th and 5th wires on your extension.

Hi, if i do this mod will i keep the stereo sound trough the headphones jacks, or all the sound in the board will be mono?

Thanks, great tutorial.

RoberMC said:

Hi, if i do this mod will i keep the stereo sound trough the headphones jacks, or all the sound in the board will be mono?

Click to expand...

The headphone jacks will keep outputting stereo.

Found my first non-MVS arcade board that appears to output stereo from the jamma edge: Arabian Magic from Taito. Only thing is, the left and right seem to be the reverse of what they are on the MVS. Odd. I wonder if there are any more. I think there's a dip setting to change it to mono. I really doubt that putting in a board like this will harm a jamma cab.

Neo Alec said:

Found my first non-MVS arcade board that appears to output stereo from the jamma edge: Arabian Magic from Taito. Only thing is, the left and right seem to be the reverse of what they are on the MVS. Odd. I wonder if there are any more. I think there's a dip setting to change it to mono. I really doubt that putting in a board like this will harm a jamma cab.

Click to expand...

Yes. Cave SH-3 boards are stereo similar to MVS.
Pin 10 is speaker +
Pin L is speaker -
Pin M is audio GND (has continuity with regular GND on Pins 1,2,27,28,A,B,e,f)

- TGM

Do the Cave boards have a 4 pin connector for the sound or do you have to use the JAMMA connector?

TheGreenMachine said:

Yes. Cave SH-3 boards are stereo similar to MVS.
Pin 10 is speaker +
Pin L is speaker -
Pin M is audio GND (has continuity with regular GND on Pins 1,2,27,28,A,B,e,f)

Click to expand...

And where would the second + channel be? This hardware (despite having a 2-channel amp, LA4708) doesn't have a switch to change pin L from sp- to sp+ (left) and doesn't have extra audio connectors afaik. I have never seen one of these boards in the flesh but there doesn't appear to be a second channel anywhere at all.

And that pin M is ground means nothing. A lot of 100% mono PCBs have it. In the original jamma pinout design that pin was meant to be audio ground for a line level mono output on pin 11. This has rarely been supported though (Atomiswave is one of the last cases I know of).

MKL said:

And where would the second + channel be? This hardware (despite having a 2-channel amp, LA4708) doesn't have a switch to change pin L from sp- to sp+ (left) and doesn't have extra audio connectors afaik. I have never seen one of these boards in the flesh but there doesn't appear to be a second channel anywhere at all.

And that pin M is ground means nothing. A lot of 100% mono PCBs have it. In the original jamma pinout design that pin was meant to be audio ground for a line level mono output on pin 11. This has rarely been supported though (Atomiswave is one of the last cases I know of).

Click to expand...

As far as I could confirm testing the board I have on hand it is stereo through the JAMMA harness, no extra header. There seem to be two distinct channels that only play properly with pins 10 and L hooked to different speakers with a GND.

I had initally spent hours fooling with the PCB trying to figure out why I wasn't getting audio with it hooked for JAMMA mono(which is what the SH-3 manusl scans I found seemed to imply it was). I eventually was pointed to some articles where other SH-3 owners saw the same thing and could only get audio when hooking pin 10 and pin M to a speaker. The previous owner also had no problems with the audio and was using the PCB in a MVS-U4. I then treated it like stereo from the JAMMA harness. That's when I finally got audio.

Unfortunately I don't have a manual with my board(Pink Sweets) and I can only find the 2 page manual scans online for other SH-3 boards(which all show the same JAMMA edge connecter setup). But it doesn't seem like they would provide any sort of diagram regardless that would allow me to absolutely confirm my testing. Some of the boards do have very tiny dip switches on them. However without knowing what they do I wouldn't be moving the position on them.