This is a loose collection describing my hobby projects in electronics over 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 focused 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 have 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 I 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 its 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 with the Plessey system a little bit, using a PC power supply and some toggle switches to simulate the power-up sequence and I got to the point of at least having an ODT prompt and I could deposit and examine data to the memory but that was pretty much it.
For almost two decades these items were kept in a cardboard box and I almost forgot about them.
In 2014 I started to look seriously into the DCJ11 and step by step I built my first PDP‐11 around the CPU. Later I started to re‐animate the Plessey system and even built some custom Q-Bus cards for this system.
Today – thanks to the Internet – it is far easier to find the required information and get help from people with the same interests. Thanks to this, I was able to finish my PDP‐11/Hack project and bring the Plessey Peripherals System to life again.