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:

[Character][Character][Character][Number][Number][Number]

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:

	Description	Heated
	Description	Directly	Indirectly
A	4V	-
B	180mA		-
C	200mA	-
D	1.2 - 1.4V		-
E	6,3 V	-
F	13V	-
G	5V	-
H	12.6V		-
K	2V		-
O	Cold cathode, used for germanium diode and transistor
P	300 mA	-
U	100mA	-
V	50mA	-
Z

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.

		Description
	A	Low power diode
	B	Double diode with common cathode (rectifier diode excluded)
	C	Triode (excluding power output triodes)
	D	Power output triode
	E	Tetrode (excluding power output tetrodes
	F	Pentode (excluding power output pentodes)
	H	Hexode, heptode (of hexode type)
	K	Octode, heptode (of octode type)
	L	L - Power output tetrode/pentode
	M	Tuning indicator
	P	Tube with secundary emission (special applications)
	Q	Enneode
	W	Half-wave rectifier diode, gas filled
	X	Full-wave rectifier diode, gas filled
	Y	Half-wave rectifier diode
	Z	Full-wave rectifier diode

The serial number consists of three figures. The first figure gives information on the type of base.

1	Miscellaneous base types
2	Miniature 10-pin base (JEDEC F10-61)
3	Octal base (I.E.C. 67-1-5a)
5	Novar/magnoval base (JEDEC E9-75 and E9-23)
8	Noval base (I.E.C. 67-1-12a)
9	Miniature 7-pin base (I.E.C. 67-1-10a)