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

Image of 6L6 beam tetrode with a glass envelope

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