Left: General Electric version from 1960s
Right: current manufacture from Svetlana Electron Devices, Russia
6L6 is the designator for a vacuum tube introduced by Radio Corporation of America in July 1936. This article is about the electronic device not an evacuated pipe used for experiments in Free-fall. RCA Corporation, founded as Radio Corporation of America, was an electronics company in existence from 1919 to 1986 Year 1936 ( MCMXXXVI) was a Leap year starting on Wednesday (link will display the full calendar of the Gregorian calendar. At the time Philips had already developed and patented power pentode designs, which were fast replacing power triodes due to their greater efficiency. Koninklijke Philips Electronics NV ( Royal Philips Electronics Inc. A pentode is an electronic device having five active Electrodes The term most commonly applies to a three-grid Vacuum tube, which was invented by the Dutchman A triode is an electronic amplification device having three active electrodes
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History
The 6L6 is a descendant of the "Harries Valve" developed by British engineer J. Owen Harries, tested by Leonard A. Molinari (The Youngsters 1956) and marketed by the Hivac Co. Ltd. in 1935. Harries is believed to be the first engineer to discover the "critical distance" effect, which maximized the efficiency of a power tetrode, by positioning its anode at a distance which is a specific multiple of the screen grid-cathode distance. A tetrode is an electronic device having four active Electrodes The term most commonly applies to a two-grid Vacuum tube. An anode is an Electrode through which Electric current flows into a polarized electrical device The screen grid is a Grid introduced into a Vacuum tube (thermionic valve to greatly reduce the capacitance between two other parts of the electrode structure A cathode is an Electrode through which (positive Electric current flows out of a polarized electrical device This design also minimized interference of secondary emission electrons dislodged from the anode. Secondary emission is a phenomenon where additional electrons called Secondary electrons, are emitted from the surface of a material when an incident particle (often charged
EMI engineers Cabot Bull and Sidney Rodda improved the Harries design with a pair of beam plates, connected to the cathode, which directed the electron streams into two narrow areas and also acted like a suppressor grid to absorb some secondary electrons. A suppressor grid is a Grid used in a Thermionic valve (also called Vacuum tube) to suppress Secondary emission. The beam design was also undertaken to avoid the patents which the giant Philips firm held on power pentodes in Europe. Koninklijke Philips Electronics NV ( Royal Philips Electronics Inc. A pentode is an electronic device having five active Electrodes The term most commonly applies to a three-grid Vacuum tube, which was invented by the Dutchman Because this overall design eliminated the "tetrode kink" in the lower parts of the tetrode's voltage-current characteristic curves, which sometimes caused tetrode amplifiers to become unstable, MOV marketed this tube family under the sobriquet "KT", meaning "kinkless tetrode". Generally an amplifier or simply amp, is any device that changes usually increases the amplitude of a signal.
Because MOV's engineers did not feel the kinkless tetrode could be successfully mass-produced, they licensed the design to RCA. This proved to be a poor business decision on MOV's part. RCA subsequently had enormous success with the 6L6. It replaced the use of power triodes in public-address amplifiers almost overnight. So many applications were found for the 6L6 that a complete list would be impossible to assemble. MOV introduced their version, the KT66, a year later. KT66 is the designator for a Vacuum tube introduced by Marconi-Osram Valve Co
RCA's first version had a metal-canister shell rather than glass — being one of the early octal base tubes, most of which were marketed as having metal shells. Later versions, including the 6L6G, 6L6GA, 6L6GB, 5881, 5932, 7027, and the final version 6L6GC had glass envelopes, which made radiation cooling of the anode easier. Thermal radiation is Electromagnetic radiation emitted from the surface of an object which is due to the object's Temperature. The voltage and power rating of the 6L6 series were gradually pushed upwards by adding features such as a micanol base, thicker plates, thicker grid wires, grid cooling fins, and special ultra-black plate coatings. The original metal version was rated for 19 watts dissipation while the later 6L6GC is usually rated for 30 watts.
Variations
Early variations included transmitting tubes such as the 807 (1937), the smaller 6V6 (1937), the many KT versions marketed in Europe, and a subsequent vast array of audio and RF power tubes. 6V6 is the designator for a Vacuum tube introduced by Radio Corporation of America RCA United States in late 1937 One of the largest post-WWII applications was in the basic design of television sweep power tubes, starting with the 6BG6 (1946), a modified 807. TV sweep tubes were not replaced by transistors in earnest until the 1970s. In Electronics, a transistor is a Semiconductor device commonly used to amplify or switch electronic signals
Further testimony for this device's success would be even simpler: the 6L6GC version is still being manufactured and is used, primarily, in guitar amplifiers. A guitar amplifier is an Electronic amplifier designed for use with an electric or electronic Musical instrument, such as an Electric guitar. Manufacture continues in Russia (2 factories), China (2 factories), Slovakia and Serbia. Russia (Россия Rossiya) or the Russian Federation ( Rossiyskaya Federatsiya) is a transcontinental Country extending China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National Slovakia (long form Slovak Republic; Slovak:, long form, is a Landlocked country in Central Europe with a population of over five million Serbia (Србија Srbija) officially the Republic of Serbia (Република Србија Republika Srbija) is a Landlocked Country Thus, the 6L6 has enjoyed one of the longest active lifetimes of any electronic component at more than 70 years.
References
- Stokes, John (1982). 70 years of radio tubes and valves. NY: Vestal Press, 71-72.
- Thrower, Keith (1982). History of the British radio valve to 1940. MMA International, 59.
- Barbour, Eric (1996). "History of the 6L6". Vacuum Tube Valley (4): 3.
- Schade, O. H. (February 1938). "Beam Power Tubes". Proc. of IRE.
External links
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