I believe it’s the CR2025 battery right under the cart bay that keeps the “save file” alive on the motherboard, providing you keep the same game plugged in (I think). Mind you, if you unplug the game, you lose it anyways.
Intentional double-post since I wanted to follow up on my issue from earlier today.
If it helps any, this is the Sega I/O that I have:
- I have the power going in the header in the top-left (+5V, +5V, +12V, +12V, Gnd, Gnd)
- I have the USB cable going where it normally does
- The main inputs (Coin, Start, U/D/L/R, buttons 1/2/3) go to their respective spots on the JAMMA edge (positions 16-24 and T-b)
Based on what I’ve found, the Kick buttons go on the header on the left, pins 4/5/6 and 8/9/10 for buttons 4/5/6 for P1 and P2 respectively. The JVS test menu’s input test seems to confirm that, as I get responses for the appropriate buttons on my sticks, or even just putting a piece of wire to those pins and grounding them.
However, in-game, and in the game-specific input test, gets me a different result.
- MvC2: all kicks don’t respond, no matter what I do.
- Rival Schools 2: like MvC2, the kicks don’t respond. What’s even weirder is in-game, P1’s Roundhouse button functions as a “System Test” button.
Looking at my board’s model number, 838-13683-92, it’s different than the number that I find all the pictures for online, which happens to be 838-13683-93.
I wonder if that’s the problem… I can’t find any info on the 838-13683-92’s pinout, though…
Lemme check my notes.
Alrighty. I’ve solved half my problem.
So I’m an idiot, and my mindset was always towards Capcom’s “Kick Harness”; ie, K1/K2/K3 on the extra harness.
And I was reading the JVS Input Test wrong.
Turns out that’s not the case on the Sega I/O.
K1/K2 (button 4/5) are directly on the JAMMA edge on pins 25/26 and c/d.
JP1 set to position “A” sets the CN3 connector as input, and pins 4/5/6 and 8/9/10 are buttons 6/7/8 for P1 and P2 respectively. So K1 should be pins 4 and 8 for P1 and P2 respectively.
However, this didn’t seem to work for me because even as before, pins 4 and 8 were wired to something that didn’t respond.
Will investigate further, as I need to figure out where button 6 is supposed to be connected…
I know this doesn’t help but on my Sega I/O ver A I could get all buttons to register except the 6th no matter what I tried. In any test menu, it always registered that button 6 was on even though I could never find the connection on the I/O board itself or on the JAMMA edge.
And final update on this. Finally found out where Button 6 goes.
So on the CN3 connector on the Sega I/O 838-13683-92 rev.B (pin 1 = the top-most pin in the corner, furthest away from the JAMMA edge):
Pin 4 = P1 button 9
Pin 5 = P1 button 8
Pin 6 = P1 button 7
Pin 7 = P1 button 6
Pin 8 = P2 button 9
Pin 9 = P2 button 8
Pin 10 = P2 button 7
Pin 11 = P2 button 6
I didn’t really test for anything else, as I didn’t need to.
Case closed!
And about 13-14 months after I first decide to start this project, I’m FINALLY done!.. for the most part.
Consolized Naomi.
Special thanks to @69mustang, @undamned, @“Jasen Hicks” and @“Lemony Vengeance”, who have all helped out in one way or other, big or small, whether they know it or not. 
Main overview, connected to my Double Sega-sticks.
Front. Nothing special here, just two USB inputs connected to @undamned’s UD-USB decoders.
Directly under are two small tact switches for the UD-USB bootloader mode. Also put in some nice rubber feet.
Back. Nothing special here either, just a flush-mounted DC-in and power switch.
Internals after taking off just the top cover; almost looks like nothing has changed.
Removal of the main board, and this is where all the magic happens.
- PicoPSU (upper right) for close proximity to the DC-in jack and power switch, and the exhaust fan
- Sega I/O rev.B (838-13683-92 model) on custom hand-made ABS stand-offs
- 2x UD-USBs (DB-15 version with no connectors)
- USB jacks and micro-tact switches on a custom ABS mount
I think I pretty much achieved all my main goals:
- Consolize the Naomi (duh!)
- No change in shape/size/silhouette (the only added protrusion is the power switch)
- Pretty much everything is modular for easy maintenance (there are connectors all over the place inside)
I left the area below the cartridge empty in case I ever want to add in something for Composite/S-Video/Component video-out at 15kHz. I should also go back and add in a couple of multi-color LEDs for the UD-USBs as well. And if I’m up for it, maybe clean up my wiring a little bit, in particular my power wires.
The only thing I’d really do differently next time is to maybe mount the power switch on the slant or underside of the casing; that way I wouldn’t disrupt the overall external shape of the case.
Next up is to mod my NetDimm…
Awesome work, as always my man If I’m seeing correctly, did you remove the socket for analog controls?
also, I’ve been talking about this very Kick button issue with a guy on the NG forums via PM and while his is a REV.B I/O that SHOULD have buttons 4/5/6 on the extension header, he also had the same config (6/7/8/9). I made him a harness for his blast city that moves buttons 4 and 5 over to the extra button harness and he was having funky input issues. The I/O he was using explains why the issues were coming up. I believe his was the same part # as yours (838-13683-92). the part just one # higher (838-13683-93) is the one that should allow for 4/5/6 over the extension header.
I like the compact size of the sega I/O, but it’s functionality over all revisions is all over the map.
I’m working on modding a console steering wheel to work via the analog port of the JVS I/O at the moment. Should be an enlightening project.
Yep, I had to remove the Analog socket to get it to fit, and I’ll be totally honest in saying that I did a pretty crappy job at it… 
Fortunately, I don’t plan to ever use this Sega I/O for anything other than this consolization, so I’ll leave it at that.
And you’re probably right on the nail with the model number of the Sega I/O; almost all the info I found online was for the 838-13683-93. And like you said, with all the versions and revisions, for the most part, most people are better off with just a Capcom I/O (which I have for my standard Naomi setup).
I look forward to see what you come up with on the steering wheel.
I would kill for that lol
Should I get the Capcom or Sega I/O converter? I want to play GDroms later on.
I won an auction for a Naomi mobo with marvel 2 for less than 7800 yen yesterday.
I have no cab and will opt for a supergun setup.
I’m a total noob at this too so any help would be appreciated.
Sega I/O is required if you want to eventually play anything that uses analogs. The kick harness needed for buttons 5-6 for each player is weird and can vary depending on which revision and which version of the Sega I/O that you have.
Capcom I/O is better (or rather, more convenient) for Capcom games; the kick harness is the same as the CPS2/CPS3 kick harness. But you lose the ability to use any analogs (ie, Super Monkey Ball). The Capcom I/O is also easier to hook up from a power standpoint but only for cartridge games: it can power the Naomi just fine via the JAMMA edge. Won’t work for netbooted or GD-ROM games; the Capcom I/O doesn’t supply enough power to the main Naomi board.
But I want to play CvS2 in the future though.
Let me elaborate, I guess I wasn’t clear enough.
You can play CvS2 on a Sega I/O; I do it just fine on my consolized Naomi (seen earlier in this thread).
You can ALSO play CvS2 on a Capcom I/O, but you’ll need a secondary power source to run your Naomi board + NetDIMM and your GD-ROM, because the Capcom I/O doesn’t supply enough power for all that.
See, the difference is that the Capcom I/O can take power off the JAMMA edge, and distribute it properly to power a Naomi board, but ONLY enough to power the Naomi board running a cartridge. It won’t supply enough power to run the Naomi board, a NetDIMM, and a GD-ROM.
A Sega I/O doesn’t distribute power at all. It can use the power off of the JAMMA edge to power itself, but it won’t distribute it to the connected Naomi board. You’ll need a separate power supply to run your Naomi board, regardless of what you have connected to it (cartridge, or NetDIMM-based gaming).
Ah okay, that makes it clearer.
I’ll hunt down a Capcom I/O then, thanks.
I would avoid going the GD-rom route. So many issues with that faulty hardware, that’s why i encourage netbooting/CF cards/Rasperry Pi methods instead. Most of the time it involves faulty lasers but you can replace the laser w/ a dreamcast one. Cool thing about netbooting is that you can also play Atomiswave games on your naomi.
Capcom I/O is the way to go & easiest but its also the most expensive one to get.
Not completely true.
http://www.arcade-projects.com/forums/index.php?thread/10-s-jihp-sega-jvs-i-o-helper-pcb/
Man its been awhile, sorry for the necro bump.
I was wondering if anyone was familiar with the dreamcast maple adapter. It allows you to use your dreamcast controller for your Naomi games. I sort of remember doing a bunch of test awhile back on games that were compatible but sadly my memory has gone to shit. The only game i got working now is Typing of the Dead. None of the other games seems to work. Im sure other games work before. Was there a certain process to do that i may have forgotten or is just plug in play like i remembered.
My main goal is trying to see if my Brooks Dreamcast adapter is compatible w/ maple adapter. Anyone know?
Should be just plug and play.
There’s a list somewhere, I remember. Let’s see if Google will help.
Google brought me back to this thread: