I picked up an old HP 7585B Pen Plotter via Craigslist. I’ve always wanted to experiment with a pen plotter. A recent visit to the Computer History Museum inspired me to poke around Craigslist to see what I could find. Sure enough, I found one for sale not far away. I’m convinced that one of the advantages of living in LA is that whatever it is you need, there’s somebody who has it. I set off with my friend Richard in u-haul pickup to go get it from a guy named Phil, who had it stored in a shipping container. Apparently he used it back in the day for printing circuit layouts which were photo-reduced and etched onto silicon. He used to design communications equipment for NASA. Funny the people you meet on Craigslist.
These old HP plotters use are controlled via a serial protocol called HPGL. I found a python library called Chiplotle by Víctor Adán and Douglas Repetto at the Columbia University Computer Music Center. Chiplotle wraps HPGL commands in a python API. So my eventual goal is to get that bridge working, so that I can generate some experimental drawings with the plotter (Frieder Nake!).
With a little googling, I found PDFs of the original manuals on the wonderful HP Computer Museum: HP 7585 User Manual & HPGL Programmers Manual (you can also find the service manual on their site).
I had some time to work on it this week, so after an hour of wiping and cleaning (why are cans of compressed air so expensive?), I got the plotter powered up and running its built-in test drawing! I’m lucky that some of the felt-tip pens that I got with the machine still had some ink in them. I probably should have take a picture of the test drawing to include here, but I didn’t. I’ll certainly do another one, so I’ll post it later.
First impressions: it worked right away, even though it’s a 32 year-old machine! Watching it draw is really fun and hypnotic. And, it’s really fast! Like, very fast. You get a sense for that at the end of this video:
https://www.youtube.com/watch?v=pRUhtlRetXM
That’s it for now, more to come. This is really my first attempt at a “build log” and also my first attempt at blogging in general. I’ll use this project as a test case to see what the process is like, and how I feel about it at the end. I hope at least that it can be a repository of knowledge that I glean from getting this thing running. I guess that depends on how google indexes this, and whether anyone interested ever finds it.
