I've redesigned the Chicago Dynamic Industries “Rifle Ricochet” sound board using modern two layer PCBs, a silkscreen, and modernized components. Uses readily available 2N3904 transistors instead of the EOLed 2N3643 and 2N3644 transistors. The #444-310 board is reproduced with better noise immunity and some extra troubleshooting features.
Known to work in "Shoot Out" and "Coney Island" EM Gun games:
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Licensed to fellow Arcade collectors under the TAPR/Non Commercial License. BOM costs are less than $20 with PCBs being ~$23.
Check my blog for the Schematics, BOMs, and a PCB order link.
http://pinball-mods.com/blogs/?p=492