Tube numbering

by Cor van Rij

The European coding scheme for tubes is does consist of two or more alphabetic characters and is followed by two or more digits:


The coding in Italic is optional. Valid examples are:
  • ECC85
  • DY85
  • PCF500
  • ECL86

The first letter classifies the tubes into series, which can be used in the same type of apparatus with regards to heater voltage or current:
A4V -
B180mA -
C200mA -
D1.2 - 1.4V -
E6,3 V -
F13V -
G5V -
H12.6V -
K2V -
OCold cathode, used for germanium diode and transistor
P300 mA -
U100mA -
V50mA -

The second letter gives information about the function for which the tube is intended. For multiple tubes i.e. tubes with two or more electrode systems, two or three letters may be combined.
ALow power diode
BDouble diode with common cathode (rectifier diode excluded)
CTriode (excluding power output triodes)
DPower output triode
ETetrode (excluding power output tetrodes
FPentode (excluding power output pentodes)
HHexode, heptode (of hexode type)
KOctode, heptode (of octode type)
LL - Power output tetrode/pentode
MTuning indicator
PTube with secundary emission (special applications)
WHalf-wave rectifier diode, gas filled
XFull-wave rectifier diode, gas filled
YHalf-wave rectifier diode
ZFull-wave rectifier diode

The serial number consists of three figures. The first figure gives information on the type of base.
1Miscellaneous base types
2Miniature 10-pin base (JEDEC F10-61)
3Octal base (I.E.C. 67-1-5a)
5Novar/magnoval base (JEDEC E9-75 and E9-23)
8Noval base (I.E.C. 67-1-12a)
9Miniature 7-pin base (I.E.C. 67-1-10a)