Recommended Gottlieb System 80 Ground Mods (Haunted House – Part 9)

Now that I’ve got Haunted House running, it’s time to bulletproof the game – ideally you’d probably want to do the ground mods from the very beginning because in some cases, you might not be able to get the game working otherwise, but in this case, I managed to get the game to boot and appear to play well, so now we’re doing the required ground modifications to make the game more stable and reliable.

What’s actually involved in that?

It’s pretty simple. Gottlieb used single-sided edge connectors (unlike Trifucon which has contacts on multiple sides) for most of their connections. Over time, these connectors tended to fail, either by the contact surface becoming oxidized, or the blades becoming fatigued and not making good contact. Since ground is so important, without a solid contact, the game can behave in a variety of different and unpredictable ways, from random reboots, to intermittent issues with everything from lights to sound to coil firing. The general rule with Gottlieb games is if you’re having a weird problem that isn’t consistently repeatable, there’s a good chance it’s related to the powertrain. The most obvious culprit in the power chain is going to be the ground/return lines.

In-a-nutshell, the ground mods involve running an extra ground wire to tie all the different board’s ground lines to a common ground, and tie the head and the cabinet ground lines together — the only exception is you keep the 45v solenoid ground line separate (this is to ensure that if there’s a coil short, it doesn’t send high voltage to the rest of the game’s more sensitive components). Each board has a different recommended spot where you should tap into the ground, often it’s near one leg of a capacitor (which should also be changed if they’re original). Use 18 gauge wire (preferably green colored) and tap into each board with one end in the designated spot, then crimp a spade terminal on the other end and tie all the boards to a single ground plane (usually the metal bracket that mounts the power supply in the upper left corner — be sure to sand the paint off the area so you can make contact (alternatively you can also solder directly to the bracket.

Once you have all the boards tied to a single plane, you want to tie that to the head and the cabinet, by running wires from the power supply bracket to the metal frame in the head, and then one down into the cabinet to the transformer board, where you’ll find a ground backplane you solder to (on System 80B games, you’ll also want to take all the ground wires that terminate on the transformer board and tie them together, preferably eliminating the molex connectors they used which cause problems).

Click at the top of each image below for larger versions:

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