Building a custom micro-controller for early Bally/Stern solid state pinball machines

This is an introduction to an up-and-coming technology that a small group of pinball and electronics enthusiasts are developing. A custom microcontroller that interfaces with Bally-35 MPUs and allows you to write customized rulesets, even completely re-theming games. This is the first part of a journey that I hope to take everybody on.

NOTE: This is a video I recorded several months ago that I forgot to make public, so I’m much further along.. But thought it might be interesting to show this early look at the development of this technology. Now there are etched boards that can be acquired.

How to properly clean battery damage off a MPU board

This is the next video in my series of work on Paragon. After the first look (http://pinballhelp.com/first-look-bally-paragon-pinball/) I discovered there were still issues with the MPU board that were the result of continued corrosion even after the battery was removed and the board was supposedly cleaned. Whoever did the previous work didn’t clean the board enough and corrosion continued. I’m going to do my best to salvage the board.

Quick demo of fully-modded Stern “Trident” pinball with new rules and sound

After getting my Trident operational, I installed the BSOS system and have been working on fine-tuning the custom code and sounds. Here’s a short demo of what the new Arduino-based controller does to a standard Bally 18/35/Stern early solid state game.

Resources (courtesy Dick Hamill):

The code is all available on GitHub. It’s broken down into a base library and then machine-specific implementations. Rewriting other games requires a moderate knowledge of C/C++.
https://github.com/BallySternOS

Here’s a suggested parts list. If you bought all these things, you could create 6 of these boards. If you don’t need that many boards, you might find cheaper ways to source smaller quantities. I haven’t done any work to figure out if this is the cheapest way to source any of this stuff.

Cheap Arduino knockoff x6 ($20.99) – needs CH340 driver for programming / has to be ATmega328P
https://www.amazon.com/ATmega328P-Controller-Module-CH340G-Arduino/dp/B08NJNJCTX/

0.1″ 40-pin connector (40 pieces for $7.99)
https://www.amazon.com/Honbay-Single-Female-Connector-Arduino/dp/B06Y4S6G29/

32-pin Prototype PCB (2 pack for $9.99) – this won’t work for Alltek or MPU-200 because they have a 34-pin connector
https://www.amazon.com/Prototype-Snappable-Arduino-Electronics-Gold-Plated/dp/B081QYPHHP/

Wire ($7.99) – tons of wire
https://www.amazon.com/REXQualis-Breadboard-Assorted-Prototyping-Circuits/dp/B081H2JQRV/

74125 – ($1.95) https://www.jameco.com/z/74125-Major-Brands-IC-74125-Quad-Tri-State-Bus-Buffer_49373.html

Boot switch – x2 ($8.99) this switch will work for activating the Arduino board and toggling the speaker (see the writeup here to find out why: https://ballysternos.github.io/install.html)
https://www.amazon.com/gp/product/B07XMH174C/

OR

@RoyGBev has created a PCB and kit (doesn’t include the Arduino) here:
https://pinside.com/pinball/market/shops/1304-roygbev-pinball/04736-arduino-nano-adapter-for-classic-bally-stern

How to make a test bench rig for Bally-18/35 MPU boards using a PC power supply

I found this old video the other day and realized I didn’t have a post on my main site showcasing this video so I wanted to add it (also, this was before I learned the proper pronunciation of “Bally” LOL…. bah-lee).

Prototyping A Brand New Mata Hari Ruleset!

I’ve been working on a new project that I’m very excited about. There’s been a movement to create an inexpensive, non-destructive and simple way to mod early Bally/Stern solid state games and add more features. In this video, I demonstrate an early prototype of the system used to modify a Bally Mata Hari pinball machine to include new features such as a skill shot, modes and even a wizard mode.

Want to learn more about this project? Visit: https://github.com/BallySternOS

Repairing/Replacing a Stern/Bally Power Supply/Rectifier Board

As part of the ongoing restoration of a 1979 Stern “Trident” pinball machine, here’s a series of videos outlining how to replace the rectifier board on these games. This varies a bit between Stern and Bally due to wire color codes. References are here.

Source: PinWiki

WPC game doesn’t boot up? Let’s diagnose this Gilligan’s Island.

You turn on your game and… “BLECH!” that’s what you get? That’s not good. Let’s try to figure out what exactly is happening:

Armed with more information, later on I have some time to pull the driver board and diagnose things further: