This is a list of vacuum tubes or thermionic valves, and low-pressure gas-filled tubes, or discharge tubes. Before the advent of semiconductor devices, thousands of tube types were used in consumer electronics. Many industrial, military or otherwise professional tubes were also produced. Only a few types are still used today, mainly in high-power, high-frequency applications and also in boutique guitar amplifiers.
Heater or filament ratings
Receiving tubes have heaters or filaments intended for direct battery operation, parallel operation off a dedicated winding on a supply transformer, or series string operation on transformer-less sets. High-power RF power tubes are directly heated. The heater voltage must be much smaller than the signal voltage on the grid and is therefore in the 5-25 V range, drawing up to hundreds of amperes from a suitable heater transformer. In some valve part number series, the voltage class of the heater is given in the part number, and a similar valve might be available with several different heater voltage ratings.
Tube bases and envelopes
Abbreviations used in this list ST – Shouldered tube GT – Glass tube MT – Miniature tube, such as Noval B9A or Miniature 7-pin B7G FL – Subminiature all-glass elliptical body and flat bases with long, inline "flying leads" (wire-ends) that are soldered into the circuit SL – Subminiature all-glass elliptical body and flat bases with short inline leads that can be soldered or can be mated with a special socket. (Flying leads can be cut short to fit into inline sockets.) R8 – Subminiature all-glass round body and base with 8 flying leads or stiff pins arranged in a circle
Numbering systems
North American systems
RETMA receiving tubes system
RETMA is the acronym for the Radio Electronic Television Manufacturers Association formed in 1953 - however the standard itself had already been in use since 1933, when RCA/Cunningham introduced the 1A6, 2A3, 2A5, etc. The first character group is a number representing the heater voltage rounded to the nearest whole number; 0 indicates a cold-cathode tube. One or two letters assigned to the devices in order of development. A single numeral that represents the number of active elements in the tube. Suffix letters distinguish revisions or variants: A, B, C – Improved backward compatible versions E – Export version G – Glass bulb, ST-12 to ST-16 size GT – Glass bulb, T-9 size GT/G – Glass bulb, T-9 size interchangeable with G and GT types L – Loctal LM – Loctal-metal LT – Locking base M – Metal envelope MG – Metal-glass ML – Metal-Loctal S – Spray shielded W – Ruggedised, or military grade WA, WB – Improved, backward compatible military/industrial variants X – Low loss ceramic base for RF use Y – Low loss mica-filled phenolic resin ("Micanol") base for RF use Lastly, manufacturers may decide to combine two type numbers into a single name, which their one device can replace, such as: 6DX8/ECL84 (6DX8 and ECL84 being identical devices under different naming schemes) or 6BC5/6CE5 (sufficiently identical devices within the RETMA naming system) and even 3A3/3B2, or 6AC5-GT/6AC5-G (where the single type number, 6AC5-GT/6AC5-G, supersedes both the 6AC5-G and the 6AC5-GT).
Often designations that differed only in their initial numerals would be identical except for heater characteristics.
For examples see below
RMA professional tubes system
The system was used in 1942–44 and assigned numbers with the base form "1A21", and is therefore also referred to as the "1A21 system".See "Decoding type numbers" ff. The first numeric character indicated the filament/heater power rating, the second alphabetic character was a code for the function, and the last 2 digits were sequentially assigned, beginning with 21
For examples see below.
EIA professional tubes system
A four-digit system was maintained by JETEC since 1944, then by EIA since 1957 for special industrial, military and professional vacuum and gas-filled tubes, and all sorts of other devices requiring to be sealed off against the external atmosphere.
Some manufacturers preceded the EIA number with a manufacturer's code: CK, RK – Raytheon Company ECG – Philips/Sylvania F – Federal Telephone and Radio (ITT division) GL – General Electric Corp. (not British General Electric Company) ML – Machlett Laboratories, Inc. NL – National Electronics, Inc. (Geneva, Illinois, USA) NU – National Union Electric Corp. (Orange, New Jersey, USA) PL – Philips N.V. SV – Svetlana: formerly only PJSC "Svetlana/ПАО Светлана", St. Petersburg, Russia now also a brand of New Sensor Corp., Long Island City, New York, USA, manufacturing in Saratov, Russia WL – Westinghouse Electric Corp. For examples see below.
Eimac transmitting tubes system Eitel-McCullough and other manufacturers of high power RF tubes use the following code since 1945: An initial digit denoting the number of electrodes: 2 – Diode 3 – Triode 4 – Tetrode 5 – Pentode Up to 2 letters denoting the construction type and the cooling method: R or a dash ("-") – Glass envelope, radiation cooling C – Ceramic envelope K – (Reflex-)Klystron P – Primarily for pulse applications L – External anode, liquid convection cooling N – External anode, natural convection air cooling S – External anode, conduction cooling V – Vapor cooled (anode is immersed in boiling water, and the steam is collected, condensed and recycled) W – Water cooled (water is pumped through an outer metal jacket thermically connected to the anode) X – Forced-air cooled (air is blown through cooling fins thermally connected to the anode) A number to indicate the maximum anode dissipation in watts. This can be exceeded for a short time, as long as the average is not exceeded over the anode's thermal time constant (typically 0.1 sec). In Class-C applications, the amplifier output power delivered to the load may be higher than the device dissipation One or more manufacturer-proprietary letters denoting the construction variant An optional digit denoting the gain group: 1 – ≤10 2 – 11...20 3 – 21...30 4 – 31...50 5 – 51...100 6 – 101...200 7 – 201...500 8 – 501...1000 Optionally a slash "/" followed by the RMA or EIA equivalent.
Examples: 3CW5000A3 – 5 kW Ceramic triode, water cooled, variant 'A', gain group 3 3CX100A5 – 100 W Ceramic UHF triode, forced-air cooled, variant 'A', gain group 5; often used by radio amateurs for 23cm-band microwave amplifiers. 3CX1500A7 (8877) – 1.5 kW Ceramic triode, forced air cooled, variant 'A', gain group 7 3CX2500A3 – 2.5 kW Ceramic triode, forced air cooled, variant 'A', gain group 3 4-65A (8165) – 65 W Glass beam tetrode 4-125A (4D21, 6155) – 125 W Glass beam tetrode 4-250A (5D22, 6156) – 110 MHz, 250 W Glass beam tetrode 4-400A – 400 W Glass beam tetrode 4-1000A (8166) – 1 kW Glass beam tetrode popular in broadcast and amateur transmitters. 4CX250B – 250 W Ceramic tetrode, forced-air cooled, version 'B', favored by radio amateurs as a final amplifier. 4CX250BC – 250 W Ceramic tetrode, forced-air cooled, version 'BC' 4CX35000 – Ceramic tetrode used in numerous 50-kW broadcast transmitters, forced-air cooled, often in a Doherty configuration as in the Continental Electronics 317C series. 5-125B/4E27A – 75 MHz, 125 W Glass power pentode 5-500A – 500 W Glass radial-beam pentode 5CX1500A – 110 MHz, 1.5 kW Ceramic radial-beam pentode, forced air cooled 5CX3000A – 150 MHz, 4.0 kW Ceramic radial-beam pentode, forced air cooled 5K70SH – 30 kW S-band Klystron
West European systems
Mullard–Philips system
This system is very descriptive of what type of device (triode, diode, pentode etc.) it is applied to, as well as the heater/filament type and the base type (octal, noval, etc.). Adhering manufacturers include AEG (de), Amperex (us), CdL (1921, French Mazda brand), CIFTE (fr, Mazda-Belvu brand), EdiSwan (uk, British Mazda brand), Radiotechnique (fr, Coprim, Miniwatt-Dario and RTC brands), Lorenz (de), MBLE(fr, nl) (be, Adzam brand), Mullard (uk), Philips (nl, Miniwatt brand), RCA (us), RFT(de, sv) (de), Siemens (de), Telefunken (de), Tesla (cz), Toshiba (ja), Tungsram (hu), Unitra (pl, Dolam, Polam and Telam brands) and Valvo(de, it) (de).
Standard tubes This part dates back to the joint valve code key () negotiated between Philips and Telefunken in 1933–34. Like the North American system the first symbol describes the heater voltage, in this case, a Roman letter rather than a number. Further Roman letters, up to three, describe the device followed by one to four numerals assigned in a semi-chronological order of type development within number ranges assigned to different base types.
If two devices share the same type designation other than the first letter (e.g. ECL82, PCL82, UCL82) they will usually be identical except for heater specifications; however there are exceptions, particularly with output types (for example, both the PL84 and UL84 differ significantly from the EL84 in certain major characteristics, although they have the same pinout and similar power rating). However, device numbers do not reveal any similarity between different type families; e.g. the triode section of an ECL82 is not related to either triode of an ECC82, whereas the triode section of an ECL86 does happen to be similar to those of an ECC83.
Pro Electron maintained a subset of the M-P system after their establishment in 1966, with only the first letters E, P for the heater, only the second letters A, B, C, D, E, F, H, K, L, M, Y, Z for the type, and issuing only three-digit numbers starting with 1, 2, 3, 5, 8, 9 for the base.
Notes: Tungsram preceded the M-P designation with the letter T, as in TAD1 for AD1; VATEA Rádiótechnikai és Villamossági Rt.-t. (VATEA Radio Technology and Electric Co. Ltd., Budapest, Hungary) preceded the M-P designation with the letter V, as in VEL5 for EL5.
First letter: heater/filament type Heater ratings for series-string, AC/DC tubes are given in milliamperes; heater ratings for parallel-string tubes are given in volts
A – 4 V heater for 2-cell lead-acid batteries and for AC mains transformers B – 180 mA DC series heater C – 200 mA AC/DC series heater D – 1.4 V DC filament for Leclanché cells, later low-voltage/low power filament/heater: 0.625 V DC directly heated for NiCd battery, series-heated two-tube designs such as hearing aids. If either filament breaks, further draining of all batteries stops"Akumed Berlin" hearing-aid eyeglasses schematic Wide range 0.9 V to 1.55 V DC directly heated for dry cells 1.25 V DC directly heated for NiCd batteries 1.25 V or 1.4 V AC from a separate heater winding on CRT horizontal-output transformers, in half-indirectly heated EHT rectifiers E – 6.3 V parallel heater; for 3-cell lead-acid vehicle crank batteries (mobile equipment) and for AC mains or horizontal-output transformers F – 12.6 V DC parallel heater for 6-cell lead-acid vehicle crank batteries G – Various heaters between 2.5 and 5.0 V AC (except 4 V) from a separate heater winding on a mains or horizontal-output transformer for the anode voltage rectifier H – 150 mA AC/DC series heater Until at least 1938: 4 V battery (as opposed to A for "4 V AC"; no known examples assigned) I – 20 V heater K – 2.0 V filament for 1-cell lead-acid batteries, later for AC transformers L – 450 mA AC/DC series heater; was shifted here from Y M – 1.9 V, directly heated N – 12.6 V, indirectly heated O – Cold cathode by 1955 this also included semiconductors as these had no heater Philips sold a family of 150mA series heater tubes under this letter in South America P – 300 mA AC/DC series heater Q – 2.4 V, indirectly heated R – Not assigned to avoid any confusion with the older Telefunken "R" system S – 1.9 V, indirectly heated T – Custom heater U – 100 mA AC/DC series heater V – 50 mA AC/DC series heater X – 600 mA AC/DC series heater Y – 450 mA AC/DC series heater, shifted to L to avoid conflicts with the professional tubes system