At the end of 2022 we finished making another Test-Case. This Test-Case showcases a number of different assemblies for producing analog sounds in pinball machines. You can, like the other Test-Cases, find this Test-Case in the Dutch Pinball Museum.


We got an old “sound board” from an early Williams SS pinball machine. The board had two chime assemblies on it, a so-called “noise unit”, a buzzer, and a knocker. To that we added a bell assembly from a Gottlieb machine, and an electronic, but analog, chime from an early Gottlieb SS Dragon pinball machine.


This Test-Cases uses the same controller board as the ones used for the first three Test-Cases. It has the exact number of high-power outputs we needed to control all the assemblies, except for the electronic chime.

The electronic chime is controlled by a small add-on board. We got lucky because the electronic chime is designed to work on a 24V DC supply, just like the solenoids. But that meant we couldn’t just connect it directly to the microcontroller’s outputs.

To overcome that problem, I made a small add-on board with three little MOSFETs on it. These MOSFETs only had to drive the 555 timer chips on the chime board, so they don’t carry a lot of current. The MOSFETs are directly controlled by the microcontroller on the main controller board.

Controller with add-on board



This Test-Case was built in the same fashion as the earlier Test-Cases we made. The case is different in one way: it is twice as wide as the earlier Test-Cases we made to properly display all assemblies inside it.

Assemblies in the Test-Case while under development


The result is a wide and “loud” Test-Case, displaying some assemblies used to produce sounds in early SS pinball machines. The Test-Case is on display in the Dutch Pinball Museum.

Test-Cases at the Dutch Pinball Museum