In order not to infringe on de Forest patents held by RCA for the grid, getter, internal insulators and the Western Electric patent for the filament material, Ralph Heintz began experimenting with a redesigned Simpson vacuum tube, whose patent was owned by his contractor, Robert Stanley Dollar. The result was the “gridless gammatron,” an electrostatically controlled tube without the now-conventional control grid.
Seven breadboard models of electronic circuits were used by Heintz & Kaufman to defend against a patent suit filed by Radio Corporation of America (RCA) in 1936, challenging Heintz’s design for the gridless gammatron. The breadboards proved the validity of H&K’s design but also suggested that RCA’s own patents were based on questionable work. RCA’s legal counsel withdrew the complaint rather than open up the question of their own patents, and Heintz and Kaufman agreed to RCA’s settlement offer of production rights for a small royalty fee.
Flier for the Heintz and Kaufman Gammatron Line, featuring the Famous 54 Series, c. 1937 (Perham Collection of Early Electronics)
Type 155 Gammatron, made by Heintz and Kaufman, c. 1929. This rare example of “gridless gammatron” had a plate dissipation of 150 watts and was built for the amateur market. (Perham Collection of Early Electronics)
Heintz and Kaufman Model 155 Gridless Gammatron. Although this model number was used on other models, this tube is clearly labeled on the glass as a 155, and is the only known example of this tube. The anode is like the model 55, with the gamma plate in the form of a cross, with two unused filaments. (Perham Collection of Early Electronics)
Heintz and Kaufman model 355 water-cooled gridless gammatron, 1928. An experimental tube, not made for production. Anode and gamma plates 4.75 inches long, 2.5 inches wide. (Perham Collection of Early Electronics)
Unmarked gridless triode prototype by Heintz & Kaufman, likely produced in 1929 in South San Francisco for their Dollaradio contract. “10A 68V” is written on glass.
Heintz & Kaufman Gammatron transmitting “half-tube.” According to notes made by John Kaar on the original Perham Foundation accession worksheet, this is an unusual tube in that it is only one half of a tube with a shield where the other half should be. The grid and plate could not go around the filament more than 180 degrees, or it would “surround” the filament and infringe on the basic tube patent. Hence, the “half” tube. (Perham Collection of Early Electronics)
Heintz & Kaufman Gammatron Type 55. No. 412 on glass, c. 1939
Heintz & Kaufman experimental Gammatron Type 103, in a RCA Radiotron UV-204-1 socket, c. 1941. This water-cooled tube would have been expensive to manufacture, and is likely an experiment or prototype. (Perham Collection of Early Electronics)
Heintz & Kaufman Gammatron Type 354, c. 1936 (Gift of Victoria Stone Velsey)
Heintz & Kaufman Gammatron Type 354 package, c. 1936 (Gift of Victoria Stone Velsey)
Trial exhibit D, one of seven breadboard exhibits used by Heintz and Kaufman, 1936 (Perham Collection of Early Electronics)
Trial exhibit E, one of seven breadboard exhibits used by Heintz and Kaufman, 1936 (Perham Collection of Early Electronics)
Trial exhibit G, one of seven breadboard exhibits used by Heintz and Kaufman, 1936 (Perham Collection of Early Electronics)
Trial exhibit H, one of seven breadboard exhibits used by Heintz and Kaufman, 1936 (Perham Collection of Early Electronics)
Trial exhibit I, one of seven breadboard exhibits used by Heintz and Kaufman, 1936 (Perham Collection of Early Electronics)
Trial exhibit J, one of seven breadboard exhibits used by Heintz and Kaufman, 1936 (Perham Collection of Early Electronics)
