Minivac 601 Replica (Version 0.9)

thingiverse

Human: Created by information theory pioneer Claude Shannon as an educational tool, the Minivac 601 Digital Computer Kit was marketed as an electromechanical digital computer system. Manufactured by Scientific Development Corporation in the early 1960s, it sold for $85.00 (approximately $720 today). The Minivac 601 used electromechanical relays as logic switches and basic storage units. Simple DPDT switches and SPDT push buttons made up the binary inputs, with lights to represent the outputs. A large motorized dial allowed users to enter decimal or hexadecimal numbers, and to output numbers, or to function as a clock signal generator. Additional resources on the Minivac 601 can be found at: * [Wikipedia](https://en.wikipedia.org/wiki/Minivac_601) * [Center for Computing History](http://www.computinghistory.org.uk/det/499/minivac-601/) * [Time-Line Computer Archive](https://t-lcarchive.org/minivac-601/) The Minivac 601 replica presented here is a full-size reproduction of the original from 1961. I have made every effort to stay true to the original design, given the available technologies and resources. Since I don't possess a vintage unit, this replica has been constructed based on photographs and online manuals. These manuals are included in PDF format as part of this project. I brought these files to a local print shop and had them printed as spiral-bound booklets that you can see above. I'm pleased with the results. **How close is this replica?** Since the original Minivac 601's frame was made from wood, I believe I've made a reasonable reproduction. The top panels of the original are unknown to me, but these replicas are 3D printed. The original used a built-in transformer and mains power, while I chose a common 12V "wall wart" for safety reasons, replacing the fuse on the Power Panel with a 2.1 mm power jack. Sourcing electronic parts was straightforward, but finding components that matched the look of the original was more challenging. I lucked out on slider switches, finding some at my local surplus store that seem identical to the originals. The lights I found at the same surplus store didn't have the right appearance, so I 3D printed "caps" for them that match the photographs better. I sourced relays that don't look too bad, and could be made to match even better by removing their clear dust covers (I chose not to). The push buttons are larger than the original's, but they're robust "arcade" style switches readily available. I designed the rotary switch specifically for this project, so it gets high marks for an authentic look. See my [Mostly 3D Printed Rotary Switch](https://www.thingiverse.com/thing:3524065) Thing for details. The biggest gap is that the *motorized* rotary switch functionality has not been implemented yet. I had a version that worked, but it wasn't reliable enough. So I'm going back to the drawing board to fix this issue. In the meantime, the rotary switch works great in manual mode. I've implemented a signaling mechanism to indicate when the motor is "engaged" and in what direction the rotor should be turned. For this version, I'm asking the operator to act as the motor. This way, all of the "experiments" listed in the three manuals can be performed. When completed, the motorized version will be a "drop-in" replacement for just the Digital Input-Output panel.