The Super Woopergun (MVS)
This is about the time I accidentally bought two Neo Geo MVS four slot boards. How do you accidentally buy two? I put down an initial bid of fifty bucks and nobody else came along to outbid me! I had to drive all the way down to San Diego to pick these things up too.
How do you use these things?
The NeoGeo MVS (henceforth just referred to as the MVS) is an arcade board designed to mount inside of an actual arcade cabinet. If you’ve ever seen a cabinet that looks like this:
These are what is inside
Yeah, it will likely be this dirty too. This thing smells like a Las Vegas casino. This one is two boards in a sandwich, with interconnects between them.
You might be looking for a standard video or audio or even a power connector on this thing. There isn’t one. Remember, these are arcade hardware. Imagine trying to wrangle all those wires one at a time. You want to unplug every single one to pull this board out? You want to manually route them through your arcade cabinet and screw them into place, doing cable management the whole way? Not gonna happen.
JAMMA
These things are designed to use a premade wire harness. All the wires are already cut, terminated, organized, and ready to be easily routed into an acrade machine. The part that plugs into the board is just a single edge connector. You can see me checking for voltage on the edge connector here:
Way easier to deal with than a million little wires. The edge connector on the MVS looks like this.
The arcade industry settled on a defacto standard called often just called JAMMA. Bit of a misnomer because JAMMA is the name of the association that came up with the standard (Japan Amusement Machine and Marketing Association , aka, 団アミュズメントマシン会), but the name has stuck. The MVS uses a slight variation on the JAMMA connector. Mostly compatible, with a couple modifications. This diagram has been taken from wiki.neogeodev.org, a fantastic resource while I was working on this project
If I was going to get any signals out of this thing, it would have to be through that.
SuperGuns
There is already a device that exists to allow you to interface a JAMMA arcade board with a regular TV.
You plug them into the JAMMA connector and they spit out regular ports for use with consumer equipment. The name, SuperGun, is pretty cool. It sounds Japanese to me, but I am unsure of where it originally came from.
There doesn’t appear to be a standardized SuperGun. The designs vary wildly. Some output composite video, some s-video, some both, some SCART, some expensive ones even do HDMI upscaling. Price also varies quite a bit. If you buy American made, expect to pay a lot of cash. Aliexpress offers very similar designs for a lot less, if you are willing to wait for shipping.
Quality for both is all over the map. Certainly some of these expensive American sellers are just dropshipping stuff from Aliexpress. At least make your own design instead of being a lazy capitalist!
Making a SuperGun
None of the superguns covered all my use cases for a reasonable price. My PVM has RGB, but each color channel is on a seperate composite cable, with sync on the composite video in. I also am friends with a retro game store owner, and I wanted him to be able to sell these with some old MVSs that he has been unable to test. He needs s-video and composite and rgb, in order for it to be attractive to customers. I have ANOTHER friend that maintains arcade equipment. They would appreciate if this could work with both normal JAMMA and the MVS variant. The designs are so close, you just need a couple jumpers to make it work. Surely I could make everyone happy
The WooperGun
This is what I ended up creating: the WooperGun. Yet another strange SuperGun made by a guy who doesn’t really know what he is doing. It covers every possible eventuality that I could ever want, and it really wasn’t that expensive to make.
There’s nothing on here that requires any kind of bespoke or overly expensive part, maybe minus the RGB to composite converter by the always expensive Analog Devices. It’s just connectors, passives, an amp, and a bunch of routing.
Design Gotchas
I was very lucky to have a bunch of members of Pawprint Prototyping help me iterate on this design. I am not an EE, I suck at anything analog. Without them, I would have been bitten by the following issues:
RGB Video Levels
The RGB video would have gone straight out of the MVS and into your TV. Apparently the MVS drives these signals SUPER hard, it would likely fry anything that’s not a PVM
Adjustment Circuitry
I did not originally include any of the trimpots, like, at all. If the colors were off, you just had to deal with it. No adjustments.
Resistor Networks
The resistor network for the Sync signal did not match the R, G, or B ones. I just copied a design from someone else. Again, a PVM probably would have handled it. Consumer TVs might be angry
Decoupling Caps
I used very small, 4.7uF decoupling caps on the video. Way too small. Again, copied from another design. Bad idea. Go for 220uF.
End Product
I have never made anything with a video signal that looks this good!
The buffers on the RGB and Sync lines as well as the RGB to Composite chip worked great. A fantastic picture, and one that I could dial in to be just right if I wanted to.
Every use case was covered. Unfortunately, when demoing it to my friend at the game store we discovered that his MVS was apparently broken all along! He never had a way to test it, turns out it never worked. Looks like a bad cap, it works for a couple seconds and then browns out and resets. I can fix that for him later.
https://codeberg.org/kaybarkbark/Woopergun
Design files for the WooperGun are, as always, open source. Please use it and copy it if it benefits you. Hopefully big N does not come after me because I put a gun in the hands of one of their precious pocket monsters.
