I recently became interested in building an RCA 1802 Microboard computer. My ultimate goal is to build a figForth based 1802 using mass storage for the word pages. I had built one back in the late 70's based on my own 44 pin back plane, Vector 44 pin plug boards and a FD controller I designed on one of the Microboards. It ran figForth quite well, but unfortunately this unit was lost to moves and life changes! I want to duplicate the function I had back then but using RCA's microboard backplane design.
There will be a series of Microboard posts as I build out my MB1802
Amazingly, someone makes compatible boards and backplanes for the RCA Microboards! Scott Pack is keeping this stuff alive and so I ordered a set of backplanes and boards to build out this project. You can review his products on his GitLab page. Contact Scott Pack <somaspack@yahoo.com> for ordering.
I received the order in very fast time. My order included kit versions that include all the passive parts, but you can also order bare boards as well. Parts included in the kit versions are also very high quality!
Backplane Assembly
The 5 slot backplanes come in two flavors:
- one with an edge connector to expand
- one without the expansion connector and breaks out three separate voltages (in case you need OP Amp or old-school RS-232 voltages.
This time around, I'm building the second one. The backplane itself is very high-quality PCB as are the 44 pin edge card connectors with integral card guides... very nice!
I soldered all the connectors on paying very close attention to alignment of the connectors. Scott's GitLab site has extensive documentation that outlines everything needed to properly assemble the backplane (and cards). After assembly of the connectors on the backplane, I set to work fabricating a support frame for the backplane. Since I want this to be fully open-frame, I elected to just build two support bars for the connectors to bolt on to. The connectors come with embedded 4/40 inserts for this purpose. I used a 12 inch x 1/4 inch x one inch aluminum bar, easily obtained at Amazon. Working at each end of the 12" bar (one side at each end is easier to handle than cutting them off before drilling) I drilled out the ten 1/8 inch holes spaced 6/10 of an inch apart and counter syncing them to accommodate 4/40 flat head screws. After bolting them to the appropriate connector sides, I added square stick-on rubber feet to complete. Finally I added a JST connector for power to the backplane and modified a Raspberry Pi 4 power switch cable to the JST plug side. This will give me a simple arrangement to bring in 5V via a USB C cable and be able to easily switch the power on and off.
