[AMRadio] Re: 6BG6 ad


ne1s ne1s at neandertech.com
Wed Mar 1 18:14:09 EST 2006


The Elmac A-54H (my mobile XMTR) uses 6L6s in the modulator. 

 -Larry/NE1S 

Jim candela writes: 

> 
> Hmmm, Well it seems like the ads claim is true, verified by Mahlon, K4OQ. In
> that case I reiterate, this is "one heck of a deal". Try pricing the 6L6GC
> from any source NOS or new, and compare. How many AM rigs use the 6L6 as
> modulators? 
> 
> Johnson Ranger (is this correct?)
> 1614
> 7027 
> 
> How many others? 
> 
>  
> 
> 
> Here are a couple more references about the 6L6 and its history, and
> descendants: 
> 
> 
> http://listserv.tempe.gov/admin/WA.EXE?A2=ind9712&L=boatanchors&D=0&P=14006 
> 
> "The first American television horizontal amplifier or "sweep" tube, the
> 6BG6G,
> came out in 1946., and was a repackaged 6L6". 
> 
>  
> 
> http://en.wikipedia.org/wiki/6L6 
> 
> 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. 
> 
> 6L6
>>From Wikipedia, the free encyclopedia
> Jump to: navigation, search
> Pair of 6L6GC tubes; (l) General Electric version from 1960s, (r) current
> manufacture from Svetlana Electron Devices, Russia 
> 
> Pair of 6L6GC tubes; (l) General Electric version from 1960s, (r) current
> manufacture from Svetlana Electron Devices, Russia 
> 
> 6L6 is the designator for a vacuum tube introduced by Radio Corporation of
> America RCA United States in July 1936. 
> 
> RCA obtained the design for the "kinkless tetrode" or Beam tetrode from
> British firm Marconi & Osram Valve (MOV) through a design share agreement,
> although RCA's own engineers were developing similar designs at that time. 
> 
> The 6L6 is a descendant of the "Harries Valve" developed by British engineer
> J. Owen Harries 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. This design also minimized interference of secondary emission
> electrons dislodged from the anode. 
> 
> 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. The beam design was also undertaken to
> avoid the patents which the giant Philips firm held on power pentodes in
> Europe. 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". 
> 
> Because MOV's engineers did not feel the kinkless tetrode could be
> successfully mass-produced, they licensed the design to RCA--which 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, KT66, a year later. 
> 
> 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 (some radio users were nervous about being injured by glass from a
> broken tube). Later versions, including the 6L6G, 6L6GA, 6L6GB, 5881, 5932,
> and the final version 6L6GC had glass envelopes, which made radiation
> cooling of the anode easier. The original metal version was rated for 19
> watts dissipation, while the 6L6GC is usually rated for 30 watts. 
> 
> The list of variations of the 6L6 design would fill a fat textbook. Early
> variations included transmitting tubes such as the 807 (1937) and the giant
> 813 (1938), the smaller 6V6 (1937), the many KT versions marketed in Europe,
> and a subsequent vast array of audio and RF power tubes. 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. 
> 
> Further testimony for this device's success would be even simpler: the 6L6GC
> version is still being manufactured and used, primarily in guitar
> amplifiers. Manufacture continues in Russia (2 factories), China (2
> factories), Slovakia and Serbia. Thus, the 6L6 has enjoyed one of the
> longest active lifetimes of any electronic component; almost 70 years. 
> 
> --
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