Vacuum Tubes in the ENIAC

The ENIAC used vacuum tubes instead of switches. The vacuum tubes were much more fragile, much more expensive, and used more power than the switches but they were quieter and faster then the switches. One of the biggest problem with the vacuum tubes was that 90% of the ENIAC's "down- time" was because of burn-outs. The burn-outs were difficult to locate and hard to replace. In one year about 19,000 vacuums had to be replaced. The average per day was about 50 vacuum tubes per day.

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