Previously, I had linked to Rory Mangles’ experiments with relay based computers. He had an incredible build of a relay logic computer called Tiny-8 which used paper as program mamory, inked with a pattern which could be read by photo sensors to sequence the control logic in his computer. I thought it was amazing. But surfing back to his website, he appears to now by working Tiny Tim, a diode-transistor logic (DTL) computer, made from discrete 2N3904 transistors and Schottky diodes. Sadly, there isn’t much actual build here yet (this update is six months old) but there is some good information, and I hope that he’ll pick up the project again.
Here is a link to his video of a simple flip flop: