6N7S (one triode), 6F6, 6J7 and 6K7 was used in the
substitutes. The electric data (except heating voltage) and the
base were the same as in old valves. Such valves are very rare
In 1946/47 the "metallic" series was extended by quite a number
of new valves. In particular, the newly produced so called "single-base
valves" appeared, which were similar
to the American 6SA7, 6SK7, 6SQ7 and later - the 6SR7 and 6SJ7.
They did not have a control grid terminal in the upper cap any
more, but due to a special construction of the base the inter-electrode
capacity did not increase at that. The letter "S" in
the second position of the marking stands for "single-base".
During the first years the valves were produced under their "native"
marking, but later they were designated as 6A7, 6K3, 6G2, 6J8
(in Russian transcription). In the author's collection there
are such valves with a Latin marking
produced in late
Octal (8 pins) valves of the metallic series. They
have a directing spigot on the base. In the USSR their production
started in 1937. Valves with 6,3V indirect heating were most widely
used. Photo shows Soviet valves 6F6, 6A7, 6K3, 6G7, 6X6, 6L7.
They were popular in the USSR till end 1950's.
1940's and a Soviet valve of the same period 6V6-GT
- the ancestor of the well-known AF output tetrode 6P6S (in Russian). The "legendary" 6P3S valve
had also undergone several modifications. Its history begins with
the metallic 6L6 valve (Russian) of 1937 make. The first version
of the home "in glass" 6L6 was no good because of overheating
of the under-sized case. The valve 6P3 (Russian, made of glass, though not having the "S"
at the end of the marking) produced in early 1950's did not show
the required quality. Only in mid-1950's
its construction was improved. That was the "classical"
6P3S already. It is produced even now with slight improvements
and bears the marking of 6P3S-E and is a valve highly thought
of among the audiophiles.
The two-anode direct heating 5C3S kenotrone has also a long history. Among its predecessors
there are both the old German valve of the "numeral"
series RGN1064 and our VO-166. Similar valves existed in the European "A"-series
(AZ1), and also in the US (5U4G, RCA80).
Soviet octal valves in the bottles. 6,3 (12,6)V indirect heating. Enjoyed a wide spread in the
USSR somewhat later than metallic ones, often being their cheaper
equivalents. Among them we can point out a group of valves with
a high heating tension for series connection of the filaments
in transformerless shemes (see "Rekord-47"). Photo shows valves 6P3, 6N7S, 5C3S, 6P6S, 6F5M,
6F6S, 6E5, horizontally - 30C6S.
valves of higher durability with metallic rings over the bases:
30P1S, 6G7S, 6X6S, 6A10S, 6S2S, 6N8S, 5Z4S.