Schematics of Atanasoff-Berry Computer logic circuits?

Not really. The ruggedized nature of computer tubes was because most were design originally for military equipment. Extra mica, beefier filament, and so forth - things not related to the cathode purity issues. ENIAC had problems because the tubes were not computer grade. I also have to wonder if the team was given tubes of lesser quality - the "M-R" types from the war years. These were tubes that were made to feed the demand outside war production, and were sometimes seconds and tubes that the War department inspector would not pass. We may never know what tubes they were given originally. When I looked at ENIAC pieces some time ago, I did notice that the thing did not use JAN qualified tubes - but they could have been swapped out years ago. Ultimately, yes, but in the 1950s, the machines were slow enough that the tiny capacitances in the structure of tube elements did not matter much. -- Will