[AMRadio] 6BG6 ad


Jim candela jcandela at prodigy.net
Wed Mar 1 07:44:30 EST 2006


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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