Introduction: Install a JAMMA Harness in an Arcade Cabinet
I have an arcade machine in a cabinet that doesn't work.
I got another board, but the pins didn't match - I figured out I needed to replace the wires.
I bought a JAMMA harness, but everything was in Chinese.
Here's how I muddled through to installing the wires to the proper places.
Step 1: What Is JAMMA?
The pins are labelled with letters and numbers
- the component side is all numbers
the solder side is all letters
- not including "i" or "o" since those are similar to numbers
- starting with capitals
- ending with lower case
- the connector has a "solder" side and a "component" side. The "component" side faces the direction all the chips on the board do
- "N/C" means "not connected" to any wires
- The "KEY SLOT" is a notch in the JAMMA board. The notch makes the connector asymmetrical so you don't connect the board upside-down. Some connectors have a plastic piece here.
- some games have 4 buttons, so pins "c" and "25" are these 4th buttons
Step 2: Why Use JAMMA?
What this means for arcade game owners is that any post-JAMMA game board ("PCB") can be plugged into any JAMMA-compliant arcade game cabinet, and it will just magically work. Pretty neat!
What is less neat is many used cabinets have been a little abused by their previous owners. Damage from players and hasty fixes may equal some pretty insane problems with the hardware.
Older games, like this IKARI Warriors cabinet, had a PCB pinout that doesn't match JAMMA. In order to use the cabinet for JAMMA games, one must replace the connector, or even rewire the entire cabinet, being careful to match each wire to the proper place on the connector.
As you can see, on my machine, not only was the original board non-JAMMA (it was a proprietary pinout used by SNK), but also someone, possibly a repairman, wired the cabinet in a THIRD pinout, which I call "sorta JAMMA." The SNK board was connected to the cabinet with this janky board. It was totally unlabeled - the pen markings are my attempt to make some sense out of the board.
The "CSI: Arcade Operator" portion of our program: from the burn marks on the GROUND connector, we can infer that the traces and board were not rated for the amount of current for the entire machine running through a single trace (oopsie!). There were four GND connections, but they weren't connected to each other, and from the look of things all the power for the entire board was going through this one connector.
The board connector fried, and rather than connect the other grounds, the operator connected another single wire to the ground, likely because they didn't know anything about how electricity works or Ohm's Law or the Joule effect - basically "if you put a lot of current through a tiny wire it will melt or catch fire." This next little wire also fried...
if you look closely you can see a similar problem happened to the +5V connection, and it was re-soldered over and over again.
The short version: I have to rehabilitate this cabinet to get my game working. I may as well get it working in a modern way that can use other games, don't you think?
Step 3: The JAMMA Harness
If you are wiring your cabinet, at some point you will have to know what every wire does. This is easier than it sounds - you literally follow the wire from where it starts, in its known position on the connector, to wherever it ends.
To make things easier to figure out, I:
- labelled the groups (with blue tape and a maker)
- put spiral wire wrapping on the larger bundles - this is a plastic spiral you can buy at Radio Shack to hold wires together
- See the big gap next to the white speaker wires? There are no wires for any of the COIN COUNTERs or lockout coils (J, K, 8, 9)
- Hard to see in this image, but the VIDEO GROUND (14) is not connected to that pin, it's connected to the main GND above
See the empty spaces next to the monitor wires?
- TILT (S) is unconnected, which is just as well, since I don't have a TILT device on the cabinet
- COIN SWITCH 1 + 2 (T, 16) are connected to the same wire, which is only connected to COIN SWITCH 1
See the blank space on the left side?
- there is no BUTTON 4 on either player (c, 25)
- the bottom 4 pins (e, f, 27, 28) are meant to be GND... but only the bottom two (f, 28) are connected
Step 4: Connecting the Power
We'll start with the easiest and most crucial wires - the power supply.
For stability of the power supply as well as to regulate heat on the board, JAMMA specifies multiple pins for each voltage:
- GROUND ("GND")
Step 5: Connecting the Video
The wires in it are color-coded and carry the signals:
- VIDEO RED
- VIDEO GREEN
- VIDEO BLUE
- VIDEO SYNC (white wire)
- VIDEO GROUND (black wire)
The monitor in my cabinet has a different jack than this harness (and I don't have the pin tool to make a new connector), so I just chopped the head off of this one and soldered the wires to the old wires already connected to the compatible jack.
Step 6: Connecting the Player Controls
Each controller has:
- Button 1
- Button 2
- Button 3
- (sometimes) Button 4
You will notice a big bundle of black wires - this is actually one continuous connection, with a bunch of terminals on it. This is GROUND for every single one of those controls.
There are two tricky things about this step:
- since 4/8-way joysticks use basic microswitches, they are mounted sideways at the corners. Therefore it can be tricky to figure out whether a switch in the upper right corner is the UP switch or the RIGHT switch. Fortunately, if you get it wrong, it will be immediately obvious when you play the game, and you can just swap the wires
The harness has 4 buttons for each player.
- My machine has 4 buttons for each player, but the 4 buttons only do 2 different functions
- My janky original adapter board wired these buttons together
- I'm going to set it up to enable 4 buttons! ...and just wire them together on the adapter
Step 7: Connect Speakers and Coin Bundles
Apparently my harness was designed for a particular cabinet configuration, and I didn't have the plugs for GND nor wherever they used P2 BUTTON 4. I asked various forums and no one knew.
Ultimately, it's irrelevant: the pins in the JAMMA standard are specified, and as long as you connect them to the proper place, it's ok. I ended up just cutting off the ends and wiring them appropriately.
- Connect the speakers - these might not have terminals on them! it doesn't actually matter which is + or -, but try to keep it straight.
- TEST/RESET and SERVICE - these are two buttons used to traverse menus in the game - for example, how many lives a player has, how many quarters are 1 credit, etc. Some cabinets don't have these buttons at all, so you can't get to the menu. My friend who has 20+ arcade games doesn't even bother with his.
- I personally like the TEST and SERVICE buttons, so I made a small plaque for them. Traditionally you put this just inside the coin door so you can service the machine easily from the front.
- the buttons are connected to the loom on one side, and to GND on the other
- TILT - another pin that doesn't get used much - on some (older) machines there was a sensor that detected if the machine was being jostled - i.e. hit by irate players. Many games don't even support this sensor. I didn't have one, so I didn't connect it to anything.
- COIN - weirdly, my harness (and others) use only one coin input for both slots, even though there is the capability for two. Most games, you can just wire them together. The other contact goes to GND.
- COIN COUNTER - there are also two of these, but even fewer get used - on some machines, there was a counter in the coin bin which counted how many coins had dropped into it. Although there are two different JAMMA pins for this purpose (one for each slot), I have never seen a counter wired to the harness.
- for whatever reason, my counter only had contacts for power - 12V and GND.
Step 8: ASIDE: Unused Wires on Loom
The two remaining wire bundles clusters:
bundle "B" here had connections to
- GND (very long)
- GND with one additional terminal
- TEST (orange)
- SERVICE (red)
COIN (green, very long)
- there's only one COIN connector for two coin slots.
- speaker + and - (white, long, no terminals)
- COIN (green, very long) - another one!
- P2 BUTTON 4? this is pin c (grey)
- GND (black, with a plug, zip-tied to another plug with 2 terminals)
Step 9: References
I had thought I'd get help from the arcade game forums... but ultimately they were pretty cliquey and not very interested in helping "outsiders." Hopefully this article will be of some use to someone!
- What To Do With Your JAMMA Harness by Bob Roberts
- an article on scratch-building a harness from wire, and connecting it to a cabinet
- JAMMA boards - a shop selling harnesses and breakout boards
- JAMMA pinout: and of course, see step 1 of this Instructable for the pinout
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