We have occasionally featured vacuum tube computers here at Hackaday ... a roughly 260 by 210 mm PCB with 24 6AU6 pentodes on board that implements a simple one-bit CPU. The architecture starts ...

[Tuval Ben Dosa] designed a complete PCB etching station that is the perfect tool for making printed circuit boards at home ... sensor encased in a silicone tube, a stir bar, diaphram pump ...