Bally/Stern MPU Test Board Version 2

7 July, 2010 (22:05) | Pinball | By: admin

A while back I designed some boards to replace the EPROMs on Bally/Stern MPUs. Once I started using it to test boards I realized that I needed to design another board geared more toward testing. What you see below is the result of this effort. It’s basically the same board but I’ve added a test LED connected to CPU address line A6, a reset LED (on when reset is high), a reset switch (which actually resets the CPU rather than triggering a non-maskable interrupt like the button on the MPU) and a jumper selectable on-board reset circuit (using Dallas DS1811 150ms reset).

These boards turned out really well. I’ve already used them to repair a couple of MPUs and I won’t consider working on a Bally/Stern MPU without one ever again. I will have a limited number of these for sale at $40 each including shipping within North America. Email me at if you would like one.