Month: September 2014

A fellow Arcade collector sent me this Private Message a few months ago on the KLOV forums:

I’ve got an old EM Chicago Coin “Shoot Out” gun game. Works great, but came without the sound PCB that generates the gunshot sound. They also made a “Coney Island” game that used the same sound PCB, but I’ve been searching for ~5 to 6 years for a used board with no success.

The problem with the soundcard is it used older End-Of-Lifed (EOL) transistors that can’t be easily found. I offered to help him design a PCB and BOM which would duplicate the sound and provide a “modernized” BOM which could be ordered off Digikey.com. He reported back that after some rework to the pinout; the card worked as expected. As a result; I’ve incorporated the rework (ie corrected the design)… and have provided the materials here for the public to duplicate and use for any older machines which are missing (or has a non-functional board) the EM Gun Soundcard used in these games.

The major changes to this board vs the original are as follows:

1. The PCB is double sided with large ground plans to aid in noise reduction.
2. Additional caps are placed on IC1 (LM380) and the Zener diode regulators to help improve the immunity of the circuit to noise. CIC1, C22, C23 – all .01uf.
3. PCB’s has both a top and bottom silk screen:
   1. Top has values and reference designators to aid in assembly and debug.
   2. Bottom has used edge fingers labeled as well as the legs of the transistors; again for debug.
4. All transistors were replaced with 2N3904 NPN transistors which are very much still in use today. The single PNP was replaced with the 2N3906.
5. Test points for the 18V, 12V, 9.1V, and ground rails are provided for easily troubleshooting the voltages on the sound board.
6. LEDs provided for the 12VAC and 30VAC lines coming into the sound card. Again quick glance that there is at least some voltage going into the sound board.
7. Although not needed in a real game; two mounting screw holes are needed if you have a non-standard installation.

I’ve decided release this design to the public under the TAPR Non-Commercial Open Hardware License which indicates:

You may make products based upon this design, provided you do not make more than ten units in any twelve month period for your personal use.

If you agree with the license terms; Schematics and BOM lists are posted here under TAPR/NCL license:
Rifle 444-310 Soundboard Package

Ordering should be easy: https://oshpark.com/shared_projects/6GKvZu4s
The boards are $67-ish for a set of 3 PCBs… and they are high quality. Gold plated fingers, two layer, silkscreen on both sides. It’s the cost of doing prototypes. OSHPark usually get the PCBs back to you in about 2 weeks.

BOM Cost from Digikey came to a WHOPPING $17 for one board. My advice is to take the BOM and multiply it by 3 in Excel or some other spreadsheet app. It’s usually cheaper to by 50 or so of the resistors. IE in one qty; they are 8cents… in 50s they are > 3cents. I usually buy 50-100 of each; just so I have them around when I prototype on breadboards and such.

The PCB is very compact; it was done this way to save on the prototype PCB sq inches cost. If you find some of your components are tight; you might try laying them similar to this:
http://pcb.bastl.sk/?page_id=50

Here’s a picture of the assembled board:

Hope this helps the EM Gun collectors out there. If it does… please drop me a comment letting me know it’s done some good!