I got HP7475A plotter on eBay. In this document I will capture some of the setup I've done to get it to work, and share tools that I use with it.

First, I replaced Geneva Drive motor attachment with a 3D printed one from here: https://drive.google.com/file/d/1VKcWApQajOygzaFmiOxXkmiYkZENntgV/view

This website had the info on how to replace the Geneva drive attachment: https://www.curiousmarc.com/computing/hp-7475a-plotter

Then, I 3D printed out a bunch of pen adapters to use with my pens. I got the files from here:

• https://www.thingiverse.com/thing:229982
• https://www.thingiverse.com/thing:1261805
• https://github.com/juliendorra/3D-printable-plotter-adapters-for-pens-and-refills

This resource has a lot of tips and tricks on getting the plotter to work: https://github.com/golanlevin/DrawingWithMachines/blob/main/machines/hp7475a/README.md