Vacuum Tube Sockets: Valve Bases

- details about the different valve / vacuum tube bases or sockets used for different valves including B7G, B9A, Octal, Loctal, UX5, UX6, UX7, etc.

Vacuum Tube / Thermionic Valves Includes:
Basics How does a tube work Vacuum tube electrodes Diode valve / tube Triode Tetrode Beam Tetrode Pentode Equivalents Pin connections Numbering systems Valve sockets / bases Travelling wave tube

Over the years there have been very many different bases or sockets used for thermionic valves / vacuum tubes.

These sockets enable the tubes to be inserted and removed very easily - very useful for times when the valves fail. It also provides a convenient method of connecting them in circuit. The sockets can be soldered rather than soldering the tubes and risking damage to them.

B4 Valve Socket
Standard name	A4A
Alternative names	British 4-pin, European 4 pin
Pins in base	4
Pin layout	16.25 mm kite
Pin diameter	3.2mm
Usage dates	1915 - to early 1930s

B5 Valve Socket
Standard name	O5A
Alternative names	British 5-pin, European 5 pin
Pins in base
Pin layout	16.25mm kite; it can be explained as a B4 valve socket with a central 5th pin added
Pin diameter	3.2mm
Usage dates	1927 - to early 1930s

B7 Valve Socket
Standard name	M7A
Alternative names	British 7 pin
Pins in base	7
Pin layout	Oval
Pin diameter	3.2mm
Usage dates	1930s, but fell into disuse when Octal valve socket / base was introduced

B7G Valve Socket
Standard name	B7G
Alternative names	Miniature, button, Mi-7
Pins in base	7
Pin layout	9.5 mm (3/8 inch) circle. 45° between pins progressing from 1 to 7; 45° between 1 and 7.
Pin diameter	1.02mm
Usage dates	1939 onwards

B9A Valve Socket
Standard name	B9A
Alternative names	Noval, miniature 9-pin, Button 9 pin
Pins in base	9
Pin layout	11.9mm (15/32 inch) circle; 36° between pins progressing from 1 to 9; 72° between 1 and 9
Pin diameter	1.02mm
Usage dates	1948 onwards

Octal Valve Socket
Standard name	K8A
Alternative names	International Octal, A08
Pins in base	8
Pin layout	17.5 mm (11/16 inch) circle spaced 45°. Central spigot diameter 7.8 mm with locating profile
Pin diameter	2.36 mm
Usage dates	1935 onwards