Coin Slot on Neo Geo - Part 2

The cheap mechanical coin mech I put on my Neo Geo cabinet is not super great, it won’t take a 20c piece at all (it’s too big to pass out the reject), and it’ll often accept a $2 coin without crediting, though that might be me not really understanding how to adjust it. I really wasn’t happy with how it looked from the outside so I started thinking… I don’t care about this broken NRI, what can I do with it? When I first got the machine I thought about trying to do something with the LED/LDR combo at the bottom of the NRI board, but now I have this extra coin switch here doing nothing….

Behold, the non-discriminating NRI g13:

First step was to remove the old board - this is a destructive process, ensuring that the NRI would certainly never work again. Unfortunately I didn’t take pictures of this step, but hopefully the process is pretty self-explanatory: Desolder the wires to the lockout solenoid, remove the solenoid, tear the board off the back of the validator, cut the ribbon cable to the front coin door. Next, I used a variety of implements of destruction to make a notch out the bottom of it, on the opposite side to where the solenoid lives:


This gave room for the wire off the coin switch to fit in place, which with a little rough bending looked something like this:


Finally, some two-party epoxy makes sure the switch stays in place (again, rough enough is good enough!):


This gives me exactly what I want - something that looks the part from the outside, accepts and credits for any coin (or slug, washer, etc, but again my needs are not great) I drop in - albeit gives you the same credit for a 10c piece as a $2 coin. Removing the credit board took some extra doing (the coin counter was connected to it instead of the motherboard, and I still don’t have a service credit button for some reason, but the original wiring is a bit of a mess so I might buy another harness and completely redo it), but otherwise everything mostly works as one would expect.

The only thing left to work out is I kinda like the idea of the lockout solenoid. I’ve ran a wire from the lockout pin on the JAMMA connector, and I can hook that up on one side of the solenoid and 12v on the other side and it works… however I’m concerned about the duty cycle of the solenoid. From looking at what’s left of my NRI, it looks like the solenoid only actuates for a brief period while the coin is accepted? Or does it close off when an invalid coin is detected? It doesn’t seem to heat up if I hold it on for a few minutes, so maybe I’m worrying for no reason… I might just solder it up and if it stops working, I can pull it out. It’s not the end of the world if I don’t have a lockout coil, as the machine doesn’t correctly credit for different coin values anyway so it’s not like I’d install it anywhere it’d serve actual paying customers… this is just for me, and because I like tinkering.

Horsham, VIC, Australia fwaggle



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Horsham, VIC, Australia

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