A while ago, I read about several efforts to create reincarnations of vintage computers, and in the process stumbled across the PiDP-8/I a recreation of Digital Equipment's PDP-8. The author, of the page a Dutch dude called Oscar who lives in Switzerland, offered a kit containing all parts, including vintage look-alike switches, a nice bamboo box and an awesome front panel. Of course, I registered my interest in buying one at once, and then forgot about it.
Two weeks ago, an e-mail arrived by the PiDP8 creator, inquiring whether I was still interested in getting one. Of course I was, and after some to and fro regarding payment, I received a parcel with the kit inside.
On his web site, there are quite detailed instructions, in particular regarding the mounting of the switches, in order for them to align properly. Overall, building the kit was not too difficult, and the instructions certainly helped. It was basically an exercise in soldering, and required soldering 27 diodes, a dozen or so resistors, a whopping 85 LEDs for the blinky lights, and finally, the 26 toggle and momentary switches.
The kit contains a bracket for them, that would help aligning the switches horizontally (to get proper alignment and equal spacing between them), and vertically above the PCB by offering solder pads for the switch tabs to be mounted (i.e. soldered) to. This didn't quite work for me. I had to align the switches vertically (i.e. height above PCB) using a ruler and used the bracket merely to help keeping a proper horizontal distance between them. Indeed, I soldered the tabs to the bracket only after having finished mounting all the switches (as opposed to doing it before as a means to hold them in place).
For the final assembly into the bamboo case, I made a few adjustments, too. The "bottom" tabs of the switches were meant to rest on the "lip" of the case. However, in this arrangement, the front panel is pushed slightly outwards, because it now rests on the tabs instead of the lip. In order to get a flush fit, I took a carpet knife and shaved about a millimeter or so off the bottom lip of the case. The bamboo case is soft, and shaving away thin pieces away from it is quite easy.
I started with thin cuts, and checked often if it was deep enough. Finally I sanded the lip smooth. Now that the tabs rest a bit deeper, the front panel sits flush in the case. Other people accomplished the same feat by bending all the bottom tabs downward, away from the lip. To me that was too fiddly, though.
Finally, I also used a different method to mount the PCB in the bamboo case. Instead of the supplied wooden blocks, I used wooden standoffs. To make them, I cut the two small wooden blocks vertically in half. They are of the correct height, but I wanted four of them. Into each of the blocks, I drilled a shallow hole with a 6mm drill bit, just wide and deep enough to receive an M3 nut. Then, I drilled a hole in the center of the recess deep enough to receive a 10mm M3 bolt (which I happened to have at hand) and epoxied-in the nut. Because there are solder connections very close to the right edge of the PCB, I cut a section away from the two right standoffs.
I then mounted the PCB onto the standoffs, and test fitted the contraption into the case. When I was satisfied that the PCB would sit just right in the case, I covered the bottom of the standoffs with epoxy glue and set them into the case. After the glue had cured I drove a screw into each of the standoffs from the back of the case for additional strength (after pre-drilling a 2mm wide hole).
I also drilled a hole for a barrel-type DC socket (as explained here), because I, too, think a micro USB socket it too fiddly for a power connector. I connected the positive rail to pins 1/2 of the extension pad and ground to 7/8.
I forgot to mention that the PiDP-8/I relies on a Raspberry Pi Zero W as its brain (the PDP-8 runs inside an emulator). The Pi Zero is perfect for this purpose: it's cheap and powerful, and fits nicely into the case. Also, because it's a "W" (i.e. has built-in WiFi) I don't need to drill any further holes in the case to connect to it.
All in all, it was a rewarding build, and the PiDP-8/I looks awesome with all those blinky lights!
