Russian tube designations
Vacuum tubes produced in the former Soviet Union - and in present-day Russia - carry their own unique designations. Some confusion has been created in 'translating' these designations as they use Cyrillic rather than latin characters.
 Receiver tubes
The 1st element (from left to right) is (for receiving tubes) a number specifying filament voltage in volts (rounded off to the nearest whole number), or (for cathode-ray tubes) the screen diagonal or diameter in cm (rounded-off to the nearest whole number).
The 2nd element is a Cyrillic character specifying the type of device:
- D (Russian: Д) - diode, including damper diodes.
- H (Russian: Х) - double diode.
- Ts (Russian: Ц) - low-power rectifier (kenotron).
- S (Russian: С) - triode.
- N (Russian: Н) - double triode.
- E (Russian: Э) - tetrode.
- P (Russian: П) - output pentode, or a beam tetrode.
- Zh (Russian: Ж) - sharp-cutoff pentode. (also transliterated sh or j)
- K (Russian: К) - variable-mu / remote-cutoff pentode.
- R (Russian: Р) - double pentode or a double tetrode.
- G (Russian: Г) - combined triode-diode.
- B (Russian: Б) - combined diode-pentode.
- F (Russian: Ф) - combined triode-pentode.
- I (Russian: И) - combined triode-hexode, triode-heptode or triode-octode.
- A (Russian: А) - pentagrid converter.
- V (Russian: В) - vacuum tube with secondary emission.
- L (Russian: Л) - cathode-ray tube.
- Ye (Russian: Е) - "magic eye" tube (e.g. used as a tuning indicator).
The 3rd element is a number - a series designator that differentiates between different devices of the same type.
The 4th element denotes vacuum tube construction (base, envelope):
- P (Russian: П) - small 9-pin or 7-pin glass envelope (22.5 or 19 mm in diameter).
- A (Russian: А) - subminiature glass envelope (5 to 8 mm in diameter) with flexible leads.
- B (Russian: Б) - subminiature glass envelope (8 to 10.2 mm in diameter) with flexible leads.
- S (Russian: С) - glass envelope (greater than 22.5 mm in diameter), typically with an octal base.
- N (Russian: Н) - nuvistor.
- K (Russian: К) - metal-ceramic envelope.
- D (Russian: Д) - glass-metal envelope with disc connections (for UHF operation).
For all-metal tubes the 4th element is omitted.
The 5th element is optional. It consists of a dash ("-") followed by a single character or a combination of characters, and denotes special characteristics (if any) of the tube:
- V (Russian: В) - increased reliability and mechanical ruggedness (such as low susceptibility to noise and microphonics).
- R (Russian: Р) - even better than V
- Ye (Russian: Е) - extended service life.
- D (Russian: Д) - exceptionally long service life.
- I (Russian: И) - optimised for "pulsed" (i.e. switching) mode of operation.
For instance, -YeV (Russian: -ЕВ) added after 6N2P (i.e. 6Н2П-ЕВ) signifies that this variant of the 6N2P has extended service life and low noise and microphonics. More often than not this means actual differences in internal construction of the tube compared to the "basic" type, but sometimes designators like -V and -I simply mean that the tube was specially selected for those characteristics from the regular-quality production at the factory.
The new designation convention was applied retrospectively to many of the previously produced types as well as to those produced afterwards. For example, a Soviet-produced copy of the 6L6 was originally manufactured in the 1940s under its American designation (in Latin lettering), or sometimes a Cyrillic transcription of it, 6Л6. Under the above convention the tube was redesignated 6P3S (Russian: 6П3С). The 6V6 tube became 6P6S (Russian: 6П6С). However, many specialised Russian tubes, such as special military or transmitter tubes, do not follow the above convention.
Some of the better-known Russian equivalents of West European and American tubes are the 6P14P (Russian: 6П14П), an EL84; 6N8S (Russian: 6Н8С), a 6SN7; and 6P3S-E (Russian: 6П3С-Е), a version of the 6L6.
 Transmitter tubes
There is another designation system for high-power tubes such as transmitter ones.
The 1st element (from left to right) is always G (Russian Г, for "generatornaya").
The 2nd element (with some notable exceptions such as the Г807) is:
- K (Russian: К) - shortwave (<= 25 MHz) tube.
- U (Russian: У) - ultra-shortwave (25-600 MHz) tube.
- S (Russian: С) - centimetric-wavelength (> 600 MHz) tube.
- M (Russian: М) - modulator tube.
- I (Russian: И) - impulse tube.
The 3rd element consists of a dash ("-") followed by the design serial number. If the tube has to be force-cooled there might follow a letter 'A' (Russian 'А') for water-cooled or 'B' (Russian 'Б') for air-cooled.
Popular transmitter tubes include the ГУ-29, ГУ-50, ГМ-70 and Г-807 (the Russian 807 analogue).
 See also
- Explanation of tube designation systems (in English)
- Russian receiver tube designation system (in Russian)