The early, first generation tube-based computers had tube failures more or less daily. Higher reliability tubes specifically intended for computers were eventua

The early, first generation tube-based computers had tube failures more or less daily. Higher reliability tubes specifically intended for computers were eventually introduced. One trick was to run the tube filaments "derated", or under the rated voltage. The tubes worked fine as logic elements at the lower voltage although that probably messed up their normal response curves. When I saw the Colossus rebuild at Bletchley Park, I asked about tube failure and they confirmed that they run the tubes (or valves, as they call them) on the Colossus at derated voltage, greatly reducing the failure rate.