The GRIDLESS GAMMATRON PROTOTYPE is a 250 watt "gridless" triode or gammatron and was a prototype tube made by Heintz & Kaufman. This construction was developed so as not to infringe with the RCA patents for the grid, getter, internal insulators and the Western Electric patent for the filament material. It was based on the work of Robert Goddard who is best known for his work with rockets. These tubes had pure tungsten filaments and tantalum plates. It has a mu of 2 and is useful as an RF or audio amplifier. According to Bill Eitel of Eimac, these were 250 watt tubes with T-32 bulbs and were the original gammatron although few were made and not for sale or for use in ship transmitters. They were all made in 1929 at 219 Natoma St. in San Francisco (Dowd, OTB Aug. 89). The term "gammatron" was later used by H&K as a brand name for their conventional line of tubes. Bill Eitel identifyed this tube as an HK-155, but another tube with a "50 watt" base was marketed by H&K as an HK-155 in later years. This has led to confusion as to the specifications for these tubes. Ralph Heintz, in 1974, didn't recall giving this tube a specific number, so the "155" number is probably incorrect.

Length = 14.00" Diameter = 3.75"
Max voltage = 3000 ?
Max current = 300 ma ?
Fil voltage = 11 ?
Fil current = 15 amps ?         GOTO INDEX