For several years, I have eyed Oscar Vermeulen’s PDP-11 replica available at Obsolescence Guaranteed. I finally pulled the trigger this fall and purchased the kit. The kit is well designed and documented:

I really took my time building this. Oscar says it takes 6 hours. I would do a little and then walk away for the rest of the day so it took me close to 2 weeks to build.

My only error was one of the many, many LEDs. Once they were soldered in, you can do a test of all LEDs. D11 was dead. After discussing this with Oscar, chances are it was the LED and nothing else so it would need to be removed.

I’m more than adequate at soldering, but desoldering is a whole other story. I was loath to remove that LED. Happily, I managed to get it out without damaging the pads. I then stuck the ‘bad’ LED on a breadboard and tested it. It worked. My heart sank – I’m sure every LED had been placed in the proper polarity.

I loose fit a replacement LED into position and it worked! Soldered and tested again and the problem was solved. I must have put that LED in backwards, though I’m sure I examined every component before soldering.

Getting the switches properly aligned was another slow task. It was not easy to get them perfectly aligned. After 2 tries, I decided that was as good as it was going to get. Honestly, I’m probably the only person that will realize the slight differences in protrusion.

Before ever starting the build, I had setup a Raspberry Pi 3 and had all of the software in place and had a good idea how the software side worked. So once the hardware build was done, I was up and running.

In my blog post Setting up a PDP-8 Emulator for Windows, I mention that I used a PDP-8 to learn assembler, but I have since learned that was wrong. I used a PDP-11. I verif