[Scott M. Baker] desires a paper tape punch for his vintage computer assortment. We are perfectly fine with that, we do not criticize. The truth is, these old-fashioned electromechanical accessories possess numerous advantages, particularly the sounds they produce. However, unfortunately, obtaining such items nowadays can be somewhat challenging, and crafting one from scratch would present a formidable task indeed. What is the solution?
Fortunately, we dwell in an era ahead of our time, and eBay showcases a variety of treasures, including these typist keyboards from the 1970s, which [Scott] promptly reverse-engineered. We will delve into the specifics shortly, but first, let us take a moment to ponder the process these devices were involved in. These are not mere computer terminals – they lack any form of input/output aside from the punched paper tape they dispensed. The operator’s duty was to enter text without any feedback confirming the correctness of keystrokes, and then would transmit the paper tape recording of the session to the typesetting machines. And you believe your job is strenuous.
In order to provide this gadget with an interface, [Scott] initially had to revive the power source, which had deteriorated capacitors. With that task completed, he commenced deciphering the CPU-less apparatus by analyzing its 7400-series logic, also devising a strategy to transform the original 6-bit output into a more comprehensible 8-bit format. Fortunately, the tape punch was already equipped with solenoids for the top two bits, but determining how to activate them was no easy feat.
The solution entailed circumventing a buffer so that the bits corresponding to the desired character could be set using a Raspberry Pi and an ATF22V10 programmable logic device. This setup was adequate to instigate the punch to carry out its intended function; conceivably connecting it to another system, maybe even [Scott]’s Heathkit H-8 computer.
