A simple JAMMA to TV hack

This is a straightforward JAMMA control panel / TV interface I built in about 4 hours the other weekend. 

A couple of days ago, I was going through our stash of arcade parts and thinking what to throw away to make more room. I ran into a Pit-Fighter control panel which I had picked up for free when we got our first batch of Mega-Techs, with the intention of 
fixing one of the cabinets to use with it. Well, it turned out that Pit-Fighter was a crap game, so I really couldn't be bothered - and thus, the huge beat-up panel had just been sitting there, taking up space.

Another thing was that I had been promised some disfunctional JAMMA boards, but had no way of testing them (Manu has our AR-1100 cabinet). Looking at the control panel, I started thinking whether it could be converted into a JAMMA testing station - and decided to give it a go. I looked at the JAMMA pinout at Game Station X (http://www.gamesx.com) and it seemed simple enough. I also stopped by the local game shop and picked up a broken SNES RGB cable with an intact 21-pin SCART connector for the TV - for 2 FIM ($ 0.30). This was a low-budget project, anyway!

Controls

I discovered that the panel still had the board connector installed. However, it had been stripped of some of the pins. Luckily, our Mega-Techs used to have JAMMA conversion kits installed, so I had a spare connector which was more suitable for my purposes. The kit consisted of a piece of veroboard where the Mega-Tech board connectors were then routed. After a while of thinking, I decided that the easiest thing to do would be to solder the wires from the Pit-Fighter controls to where the Mega-Tech wires had been and leave the JAMMA connector itself untouched.

Pit-Fighter has 3 players, the 3P controls are connected to the game board with an extra connector. I decided to use the leftmost and rightmost sticks & buttons, so the players
would have more room. It was a question of simply moving the connectors from the centre stick to the rightmost one. The centre stick does nothing at the moment, and never will, but the buttons act as Start 1P and 2P. I'm thinking of wiring "Coin 1" to the middle button just in case I get a board that won't do freeplay.

The sticks, although they do work, are nothing to write home about at the moment, and I'm thinking of replacing and/or cleaning them.

Power

For power, I decided to use a PC supply. Since, while actually collecting non-PC computers, we had accumulated quite a pile of old PCs, it wasn't a huge problem to find a power supply that provided me with +5V & +12V. I gutted an Olivetti 286 with a broken motherboard -  despite the non-standard connector, the PSU had ample quantities of everything I needed and it fit nicely inside the case. I left -5V unconnected, since that's not used by the game board - only the coin mechs which I didn't have.

A bit of a problem was that the power switch was attached to the front of the PSU, and I had to install it pointing inwards to get the mains cord to fit. Alas, now I have to stick my hand inside the thing to switch it on. Removing the centre stick will alleviate this problem, though, since the switch is located directly below it.

Attaching the board

The Mega-Techs also used to have plastic rigs for quick installation of the JAMMA boards, and I thought they would be ideal for this project. However, there was no space for the
board inside the case, and I didn't want to make the thing any bigger than it already was. The panel had originally had a space for the board, but I had taken it apart since it was extremely bulky and heavy. 

After a bit of thinking and browsing through our stuff, I found a badly beat-up Mega-Tech control panel. It did, however, have a working long hinge installed. I took out the hinge and attached it to a piece of plywood I cut out of an old bookshelf (the white bit in the picture), installed the plastic rig onto it and connected the whole thing to the back of the control panel. This way, you can fold the unit so it takes up less shelfspace. 

Signal output

I had decided very early on that I wanted to use the SCART connector found on most European TVs. It allows me to use the device anywhere without a dedicated monitor. I found a great
SCART pinout at www.diyha.co.uk and used it to wire the pins - easy job, since the connector accepts R,G,B, sync and ground as well as audio. I used an old modem cable to make the
SCART lead, it had sufficient pins (a total of 7 required) and was, again, free. The picture and sound quality is very nice on a Philips SCART monitor, I've yet to try it on a bigger TV.

Outcome

Building the device was surprisingly easy, and I recommend it to anyone with basic electronic skills. The total cost of the project for me was said $0.30, everything else was recycled. It helped a great deal to have all these parts lying around, but you can find all the necessary stuff at any electronic parts dealer for reasonable prices. Seeing as you can get early '90s JAMMA boards for less than 200 FIM ($30) even in Finland, this is a nice piece of kit to have handy, especially as it only takes up a fraction of the space of an arcade cabinet.