It’s hard to believe, but I remember when vacuum tubes were viable circuit elements. Yes, I’m that old. At about age 13, I began repairing and constructing vacuum tube circuits in 1959. Transistor prices fell rapidly and quickly replaced vacuum tubes in low power, low speed applications. Tubes remained viable in high frequency applications above 100 Watts through the 1970s. Transistors and integrated circuits pushed out vacuum tubes everywhere else.
High power transmitting tubes glowed magically. 250TH and 304TH plates lit up with dull orange to bright yellow colors as a function of plate current. 4-1000 plates glowed cherry red to pumpkin orange. Mercury vapor rectifier tubes such as 866s and 872s lit up their trapped vapors with a beautiful blue glow.
This Western Electric film from 1940 takes us through their vacuum tube manufacturing processes. They include a surprising number of skilled hand labor operations. Note how many women performed these delicate tasks.
Seven years after this film’s release, John Bardeen, Walter Brattain, and William Shockley co-invented the transistor. Today even 50 kilowatt transmitters are entirely solid-state.
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© Russ Bellew · Fort Lauderdale, Florida, USA · phone 954 873-4695