Schematics of Atanasoff-Berry Computer logic circuits?

William> I'm not very familiar with vacuum tube circuit design, but I William> have a PDF copy of the 1952 USAF technical order TO16-1-255 William> "Basic Theory and Application of Electron Tubes" which looks William> like it might be sufficient. Is that on line, or could you post it? William> I've built two different 12AU7 William> dual triode vacuum tube stereo headphone amps from plans William> which use much lower and, therefore, safer and William> easier-to-produce voltages (24 - 60V) than were used William> historically in such circuits. The required plate voltages William> for these low-power circuits are produced using simple William> voltage multipliers attached to commonly available and William> inexpensive low-voltage transformer secondaries. Since, in William> the case of digital logic circuits linearity of operation is William> not a requirement as it is with audio circuits, even lower William> voltages might be usable although 24 volts seems to be William> plenty low enough. Logic circuits are DC coupled, though, unlike audio amplifiers. So the shift in operating point from the plate voltage change (or, for that matter, from a change in vacuum tube type, if you're doing that) probably means you'd have to change all the coupling resistors. I found some work on the net (and did some of my own based on that) on Spice models for vacuum tubes. It's not a standard offering in Spice packages but it's easy enough to define a model, and given a data sheet with characteristics curves you can quickly match the model to the data sheet. (The circuit I'm modeling is being very uncooperative, but as far as I can tell the tube models are not at fault in this.) Spice might be a handy way to verify an existing schematic and to discover how to tweak it for another tube and/or another plate voltage. paul