The Method in Their Madness.
We who live in North America are accustomed to our "number-letter-number" system of tube designations. Our system is probably as baffling to the Europeans as theirs is to us. Just as there is method in our madness there is also method in theirs. Thanks to Mike (Mac) McCarty here is a description of the European system of valve type designations.
European Valve Numbering Convention for Consumer Valves.
The first letter indicates the heater supply.
A: 4V.
B: 180mA, various voltages.
C: 200mA, various voltages.
D: 0.625A, 1, 2 or 1.4V.
E: 6.3V.
F: 12.6V.
G: 5 V (Various currents?) .
K: 2V.
L: various voltages and currents (very old types) [450mA, various voltages?] .
M: 2, 5 V.
P: 300mA, various voltages.
U: 100mA, various voltages.
V: 50mA, various voltages.
X: 600 mA.
Y: 450mA, various voltages.
The types where a current is stated, are series connected and connected directly to the 120V or 220V mains supply. They where used for low-cost radios and TV's.
The second letter(s) indicate the tube type.
A: signal diode.
B: double signal diode.
C: low-power triode.
D: power triode.
E: low-power tetrode.
F: low-power pentode.
H: hexode or heptode (of the hexode type) .
K: octode or pentagrid tube (= heptode of the octode type) .
L: power tetrode or pentode.
M: indicator tube.
P: secondary emission tube.
Q: enneode.
W: half wave gasfilled rectifier.
X: full wave gasfilled rectifier.
Y: half-wave rectifier.
Z: full-wave rectifier.
The first figure indicates the socket type.
1: various types.
2: decal (miniature 10-pin).
3: octal 8-pin.
4: rimlock 8-pin.
5: magnoval 9-pin.
6: enne-al 9-pin.
7 is also a "miscellaneous", the EM71 magic eye has a loktal base.
8: noval (miniature 9-pin) .
9: miniature 7-pin.
1...9 pinch based tubesystem; pin- side- or octal-socket (often side contact of the 'P type').
11..19 pinch or pressed glass based tubesystem with steel or glass envelope. (often referred to as the 'German steel series' with G8A socket).
20..29 pressed glass based tubesystem with Loctal socket (B8G).
30..39 pressed glass or pinch based tubesystem with Octal socket.
40..49 pressed glass based miniature system with Rimlock socket (B8A).
50..60 often 9 pin Loctal (B9G) socket or special sockets.
61..69 5 pin sub-miniature socket round or in-line.
70..79 8 pin sub-miniature socket round or in- line or 8 pin Loctal socket.
80..89 and 180..189 9 pin Noval miniature socket (B9A).
90..99 and 190..199 7 pin miniature socket (B7G).
This scheme came into effect around the mid-thirties. Tubes manufactured or developed before that time had, and often kept, a manufacturer based coding. The last figure(s) are the tube type number.
From 1963 the system was streamlined to basically a 2 letter/ 3 figure system based on the same coding system as above. Tubes developed from that time onwards where mainly: the tubes in the 500 series which had a Magnoval socket (B9D), the 200 series which had a Decal (10 pin miniature) socket and the 800 series with a Noval (B9A) socket. Tubes in the 900 series had a 7 pin miniature socket.
The last of the three figures indicates the kind of characteristic except for power tubes.
-An even figure indicates a sharp cut-off tube and an odd figure indicates a variable-mu characteristic.
There are some deviations from the scheme, like ECC2000.
There are (of course) some exceptions to the rules. Some tubes have a "1" in front of the number, ECC189 for instance. It is still the 8 that indicates the socket type.
I hope this information is helpful and hopefully complete. The information is from the Philips Pocketbook 1968.
Ballast tubes have only one letter representing the current series.
The transmitting scheme :
First letter :
D : Rectifier.
M : Triode (AF amp or modulator).
P : Pentode.
Q : Tetrode.
T : Triode (RF,AF or osc).
Second letter (third in dual tubes ie QQE06/40).
A : Directly heated tungsten filament.
B : DH thoriated tungsten.
C : DH oxide.
E : Indirectly heated oxide.
First figure group.
Rectifiers : Approx DC output voltage (in KV) in a 3 phase rectifier. TX tubes : Approx max anode voltage (in KV),Second figure group.
Rectifiers : Approx DC output power (in W or KW) per tube in 3 phase circuit.
RF tubes : Approx output power (in W or KW) in class C telegraphy.
Modulators : Approx anode dissipation (in W or KW).