How to Connect a Jamma Harness

So, you have built the ultimate arcade cabinet, purchased a whole bunch of electronic hardware, and now all you need to do is wire it altogether. Here's some helpful tips.


  1. Image titled Connect a Jamma Harness Step 1
    First thing you need is a JAMMA harness. This is a standard edge connector with two rows of 28 pins used on almost all arcade machines.
  2. Image titled Connect a Jamma Harness Step 2
    The JAMMA harness has a standardised wiring code as follows:
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Solder Side Parts Side
ground A 1 ground
ground B 2 ground
+5VDC C 3 +5VDC
+5VDC D 4 +5VDC
-5VDC E 5 -5VDC
+12VDC F 6 +12VDC
key slot H 7 key slot
Coin counter #2 J 8 Coin counter#1
Lock out #2 K 9 Lock out #1
Speaker (-) L 10 Speaker (+)
N/C M 11 N/C
Video green N 12 Video red
Video sync P 13 Video blue
Service switch R 14 Video ground
Tilt(SLAM) Switch S 15 Test switch
Coin switch #2 T 16 Coin switch #1
Player 2 - START U 17 Player 1 - Start
Player 2 - UP V 18 Player 1 - up
Player 2 - DOWN W 19 Player 1 - Down
Player 2 - LEFT X 20 Player 1 - Left
Player 2 - RIGHT Y 21 Player 1 - Right
Player 2 - Button 1 Z 22 Player 1 - Button 1
Player 2 - Button 2 a 23 Player 1 - Button 2
Player 2 - Button 3 b 24 Player 1 - Button 3
N/C c 25 N/C
N/C d 26 N/C
Ground e 27 Ground
Ground f 28 Ground
Image titled Connect a Jamma Harness Step 3
  1. Image titled Connect a Jamma Harness Step 4
    Physically push the connector onto your JAMMA board. The connector and board are usually 'keyed' at the place where pin 7 would be, so that they will only go on one way. Sometimes the connectors are not keyed and it is possible to put it on the wrong way around.
  2. Image titled Connect a Jamma Harness Step 5
    One way to tell which way around the connector goes is to locate the wires for the power supply as these will have different terminals to the wires for the controls; the JAMMA board will usually have the pinouts labelled if there is no key. The cables for the power supply will go to the left of the keyslot on the board.
  3. Image titled Connect a Jamma Harness Step 6
    Press the connector firmly onto the board. If it is a loose fit a blob of hot melt glue will be needed to hold it in place, do not use chewing gum even if it seems to work at first the chewing gum will attract all manner of crawlies that will set up home inside your cabinet and cause trouble down the line.
  4. Image titled Connect a Jamma Harness Step 7
    Now gather the wires up into groups, for example: player 1 controls, player 2 controls. A good tip is to temporarily bundle these using elastic bands. Once bundled you can more easily sort out which wire needs to go where. Take your time and use plenty of cable ties to keep it all tidy.
  5. Image titled Connect a Jamma Harness Step 8
    If your board has a built in test mode then it is a good idea to have it switched on before connecting up the controls. That way you can actually test that you have the right wire going to the correct control at you wire it up, rather than having to back trace any mistakes later. Don't worry about working with live wires; provided that you have the power supply properly connected and isolated, you are only working with wires carrying a tiny current.
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    Once connected, enjoy playing your favourite games.

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Categories: Cabling and Wiring Connection