In my attempts to collect as many Control Panels as possible for my Sega New Net City cabinet I eventually came up on a Mahjong panel. The problem with these panels, is the wiring is REAL weird. I had been combing eBay for reasonably priced specialty panels when I found this one for $75. The problem for me is that I had not seen any documentation on getting one installed in a New Net City, most of what I saw was for Astro City, and Taito Egret cabs.
A guy named “andynumbers” shared what seems to be one of the more complete accounts of how to get these panels connected. In this piece he mentions some interesting history on this type of panel. Knowing for example that “Mahjong boards use the same 56-pin edge connector that JAMMA boards use, but the pinout is completely different” is important. The “matrix” style input is important to understand as it can ultimately mean your success vs. failure if you don’t grok how it works. As an example the blog above mentions that ”mahjong games on the NAOMI system use a JAMMA pinout with the matrix inputs mapped to the button inputs”, knowing that is also pretty key to success.
Once the panel arrived I was unable to do anything with it input wise, I flat out could not figure out how to get the inputs to work. The best I could do was cause the standard JVS I/O input menu to trigger all 1’s if I mashed nearly all of the buttons in tandem. They were clearly connected to what appear to be a standard “Charlieplex” style input. After multiple failed attempts at wiring the panel into my New Net City AMP-UP connectors I shelved the whole setup while I read up a bit more. At this point I was unable to use the game test menu, as it was in Japanese (later I found Google Translate via Camera to be useful), so I was dead in the water. I had also ruined the original AMP wiring order having failed to document it!
Eventually after more hunting I ran across a SOPHIA CORPORATION listing that included both a Mahjong game, and an “extended harness” of some sort. Lucky for me this harness saved my tail on the restoration of the AMP wiring order, on random luck it happened to use the same color code. It turns out this color code is semi-universal in the Mahjong space, as somehow it directly relates to the “matrix”. In my correspondence with SOHPIA CORP. staff I learned that “this software requires… JVS/JAMMA I/O board… And in addition, Mahjong game requires Mahjong panel and wiring to the JVS/JAMMA I/O board”. This specific purchase came with a harness “for Sega Asro, Blast, Versus and Megalo 50 cabinet”, although useful, I was not able to use it in my setup at all. I had to hack up my own cable set. This cable did however give me an epiphany on the setup. Once the manual arrived I noticed the IO board was indeed the old JAMMA to JVS variant. This harness was connected to the IO board on its CN7 header. The IO board was easy to identify because of the JAMMA, the JP1 switch, and CN7 usage it was obviously a Sega 838-13683-93 board. The manual further confirmed suspicions, and pinouts.
I had remembered seeing this IO board with a Taito Type-X Mahjong setup, and lucky for me the resulting blog cinched up the final setup for my Naomi. Author AeroCityMayor provided the pieces that andynumbers left out. The words “Put simply, the Mahjong CP is connected to the Type-X¹ via a REV. B SEGA JAMMA I/O. The multiplexed inputs are connected via pins 17-22 on the parts side of the JAMMA loom and pins 4-8 on CN3 in the I/O.” finally made sense. The diagram for the multiplex matrix also made sense, as such I made a cable to fix my cabinet up to be able to play Mahjong once and for all. I removed the split connector setup, and used one 12 pin AMP-UP, and then wired that to a JAMMA Edge connector, and to a JST-H connector for the additional inputs. I matched all the colors up accordingly, and it worked great! The one thing to note is that the normal JVS IO screen will not properly show the inputs, you actually need to load the game and use its test menu to verify the wiring.