In the early 1960s, “real” computers were so large and expensive that it was virtually unheard of for any individual to have one at home. But, of course, people still needed a way to learn about the principles of digital computing. For a lot of people, that meant receiving training at one of the few companies or universities with a computer. For others, that meant using far more affordable educational devices that could provide the functions of an extremely basic computer. The Minivac 601 was one such device, and Megardi has a tutorial that will walk you through how to build your own replica.
Unlike modern computers which use transistors as logic switches, the Minivac 601 used electromechanical relays. Considering that a processor today can have billions of transistors, the idea of using relays in their place is unthinkable. But when the Minivac 601 was released in 1961, it was cheaper to use a handful of electromechanical relays than transistors, which were still cutting-edge technology at the time. The Minivac 601 used DPDT switches and SPDT push buttons as binary outputs, and lights as outputs. A special motorized dial was used to enter decimal or hexadecimal numbers, and also acted as an output.
Megardi’s replica of the Minivac 601 seems to be extremely faithful — both in appearance and functionality. To build it, you should only need a 3D printer and basic woodworking tools. The electrical components may be a little difficult to source, but Megardi was able to find parts that closely match the originals. The only major exception is the dial, which Megardi hasn’t been able to motorize yet. It can still be used like the original, but requires that the user move the dial manually. If you want to experience some very early computing history for yourself, this is a fantastic way to do so.