REFERENCE INFRORMATION

In the 1950s a 5-element system (GOST 5461-59, later 13393-76) was adopted in the (then) Soviet Union for designating receiver vacuum tubes.

The first element – number, means a filament voltage in volt (approximately).
The second element – letter, designating type of the device:

D – diode, including dempfers;
H – double diode;
C – low-power kenotron;
S – triode;
N – double triode;
E – tetrode;
P – output pentode and beam tetrode;
J – high-frequency pentode with short characteristic, including with double management;
K – high-frequency pentode with long characteristic;
R – double tetrode and double pentode;
G – diode-triode;
B – diode-pentode;
F – triode-pentode;
I – triode-geksode, triode-geptode, triode-oktode;
A – frequency-converting tubes and tubes with two operating grids (except for pentodes with double management);
V – tubes with secondary issue;
L – tubes with focused beam;
E – electron-beam indicators of adjustment.

For electronic mehatrons the second element of a designation is made of three letters: the first M – mehatron; the second letter corresponds to the basic purpose of the device (in some designations mehatrons, developed earlier, this letter is absent); the third letter designates type of the device according to the list resulted above.

The third element – number, corresponding a serial number of the given type of a tubes.
The fourth element – letter, describing constructive desing of a tubes:

P – in a glass environment, tiny (finger-type), diameter 19 and 22.5 mm;
A – in a glass environment, supertiny, diameter from 5 up to 8 mm;
B – in a glass environment, supertiny, diameter from above 8 up to 10.2 mm;
G – in a glass environment, supertiny, diameter over 10.2 mm;
S – in a glass environment, with a socle or without a socle, diameter more than 22.5 mm;
N – in a ceramic-metal environment, tiny and supertiny;
K – in a ceramic environment;

Tubes in metal to an environment of the fourth element of a designation no have.

Additional element. To a standard designation of a tube are sometimes added (after a hyphen) the letters describing special properties of tubes, for example:

V – increased reliability and mechanical ruggedness (such as low susceptibility to noise and microphonics);
R – even better than V, extra high reliability (10000 hours and more);
E – extended service life (5000 hours and more);
D – exceptionally long service life;
I – optimised for “pulsed” (i.e. switching) mode of operation.

Example for 6P14P-ER tube:

6 – filament voltage, 6,3V;
P – output pentode;
14 – serial number of type of a tube;
P – envelope: miniature, glass;
ER – raised durability, operation time > 10000h

There is another designation system for high-power tubes such as transmitter ones.

The first element (from left to right) is always G.

The second element (with some notable exceptions such as the G-807) is:

K – shortwave (≤ 25 MHz) tube;
U – ultra-shortwave (25–600 MHz) tube;
S – centimetric-wavelength (> 600 MHz) tube;
M – modulator tube;
I – impulse tube.

The third element consists of a dash (“-“) followed by the design serial number. Letter can be used here in some special cases (GMI-6 – impulse modulator); if the tube has to be force-cooled, there might follow a letter A for water-cooled or B for air-cooled.

Popular transmitter tubes include the GU-29, GU-50, GM-70 and G-807 (the Russian 807 analogue).