I have conquered the Motorola 6820/6821 peripheral interface adapter!
Last week I got another batch of prototype PCBs and one of them was the latest version of my Bally/Stern CPU socket based daughter board that adds a microcontroller connected to all of the CPU pins needed to let the microcontroller run in parallel with the original [...]

If you are ever in Las Vegas you owe it to yourself to visit the pinball hall of fame. I was lucky enough to visit the pinball hall of fame on 2 occasions over the 4 days that I was in Las Vegas. I played about 90% of the machines that were available and had [...]

Part 2 of the Pinball Hall Of Fame pictures:

Update Aug. 21: Looks like you can replace the original 470pf capacitors on -17, -13 and MPU-100 MPUs with 220pf to convert them to the MPU-200 clock speed. I will try to get an oscilloscope image of this conversion but it’s 2 less components to replace.
I was inspired by this thread on RGP to [...]

Recently I have been experimenting with methods to replace the EPROMs on Bally/Stern MPUs with a single EPROM. This is the direction I’m planning to go with the more advanced version of my MPU daughter boards. Initially I was planning to use a 2764 EPROM to replace the original 2x 2732 EPROMs but the Motorola [...]

NOTE: Procedure was updated July 30, 2010.
While looking at the Stern MPU200 schematic trying to figure out how I was going to add RAM to my MPU daughter boards I realized how easy it would be to install a 6116 SRAM in one of the unused EPROM sockets to replace the 5101. This replaces [...]

A lot of my projects are finally starting to come together. These boards are another step toward a dedicated lamp driver board testing system. These boards connect to J1, J2 or J3 on the lamp driver board and connect an LED to each SCR output. There is a chart screened on the board that shows [...]

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 [...]

Recently the company that I’ve been renting my warehouse space from needed to use the space for their own storage so I was forced to move out. Most of the pinball machines I had stored there are now being stored in my basement and I’m planning to restore and sell 50+ machines over the next [...]

I picked up these 2 Mousin’ Around pinballs the other day. For the price I couldn’t turn it down. I made a short video showing how I load and unload games by myself. I’m not sure when these machines will be restored but I’m hoping it will be some time in the next couple of [...]