Coin Reject / Credit Button Hack
I have been wondering for some time how to add dedicated "credit" switches to my cab, so my guests wouldn't have to be bothered with remembering the I-PAC shift key for inserting coins, or constantly plunking tokens into the machine. I really hate the idea of adding extra buttons for MAME functions onto my control panel, so I wanted them to be logical and inconspicuous. Then it dawned on me that there are 2 buttons on almost every cabinet that go unused as inputs -- the coin reject butons! Hmmm....
A quick fumble thru the spare-parts bin turned up 2 small microswitches with roller levers. I cut off two small chunks of wood to be used as mounting spacers (about 1.5" x 3/4" x 1/4") and screwed the switches securely in place on the wood. Then I placed double-sided foam tape on the backs of the wood blocks, and pressed them into place on the upper coin chutes, positioning them so that the switch actuators are in contact with the yellow plastic wedges that get pushed down by the red reject buttons. The switches are wired NC, so the switch is actually open while the yellow wedge is pressing on the actuator arm. When the reject button is pressed, the yellow wedge tips downward, releasing the actuator, and allowing the credit switch to close! The reject buttons only need to be pressed in about 1/8" before the actuator gets released, so a large amount of credits can be quickly racked up!
The two reject microswitches are wired in parallel with the main coin mech switches, so under normal conditions, either pressing the coin rejects or inserting tokens into the slots will trigger credits in MAME. In addition, I added a "cut-off" switch between the reject switches an the coin mechs (the red "TEST" switch in the upper right corner), allowing me to "cut" the ground wire (green wire across top) that runs to the reject button microswitches, so that tokens MUST be used to play games if I want. Here is a simplified schematic:
Obviously, I am using the reject buttons
as the 5 and 6 buttons in MAME, but you could wire them to act as any two
buttons. They could be secret shift or shazam buttons for
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