Tuesday, 16 March 2010

Passive JAMMA auto fire circuit

A passive auto fire circuit built around a 74HC04 Hex inverter. Not truly passive but does not require and additional 5 or 12 v from the JAMMA harness.

Original circuit. (courtesy of emphatic, purchased from Yahoo Japan auctions)

Schematic derived from the above

PCB layout. Due to the cost involved in manufacturing PCBs is probably isn't worth the cost, anyway it only took 10 minutes to knock up. PCB size, 40 x 28mm. ^_^

Completed circuit assembled on Veroboard with spade connectors for easy installation.

Prototype circuit next to a ¥100 coin for size reference. The 10k pot adjusts the rate from zero to around 60Hz.

Both the above circuits were constructed with 2 x 100u Capacitors due to stock shortages. The circuit still works but the results aren't quite as good.


  1. just a stupid question:

    which connector do you plug on the "button side" ? SW1 or SW2 ? (i guess the other one goes on the "pcb side"...)

    thanks! M68

  2. For the bottom most picture. Remove the grounds from the two buttons you would like to use and attach the yellow wires. Attach the green wire to one of the removes ground wires.

    Good to go mt8.

  3. Hello,
    Why didn't you choose to tap the +5V from the jamma finger board ? It would allow for a more complex type of autofire, methinks.