About

This is a loose collection describing my hobby projects in electronics of the past few years. I started with electronics a long time ago at a time when the technology was not as widespread as it is today. Transistors were very expensive and using 74xx as a hobbyist was the bleeding edge. Later I irregularly got back to this hobby but only since about five years I was seriously resuming the hobby again. And since three years I have focussed on PDP‐11 related projects which will be the most important topic of this web page.

I’m a big fan of PDP‐11 and for a long time I always wished that I could own one and be able to run RSX‐11M on it, which was the operating system that I was using at my first job.

At some stage I owned a PRO‐380 and even some parts of a small Plessey Peripherals system.

The PRO‐380 is gone as it someday no longer worked and I did not have the time, documents and means to repair it, so I dumped it, but only after a desoldered the DCJ11. Later this DCJ11 would turn into the reason I started with my PDP‐11/Hack project.

The Plessey Peripherals system was missing all of it’s peripherals and my know‐how about PDP‐11 hardware at that time was not sufficient to turn it into a real system. At the beginning I used to play a little bit with the Plessey system using a PC power supply and some toggle switches to simulate the power up sequence and I got at least to the point of having an ODT prompt and could deposit and examine data to the memory but that was it pretty much.

For almost two decades these items were kept in a cardboard box and I almost forgot about them.

Then in 2014 I started to seriously looking into the DCJ11 and step by step built my first PDP‐11 around the CPU. Later I started to re‐animate the Plessey system.

Today thanks to the Internet it is far easier to find the required information and get help from people with the same interest. Thanks to this I was able to finish my PDP‐11/Hack project and bring the Plessey Peripherals System to live again.