S625 dull emitter screened HF amplifying valve

This valve measures 126x34mm overall. It has a 2 pin base at one and and a 3 pin base at the other.

The S625 screen grid valve was designed to be used horizontally with the anode and grid circuits screened from each other. The valve would be mounted in a hole in the screen so the screen and the screen grid itself were aligned.

It was announced in September 1927 as the most remarkable valve development of the year.

However it was not particularly popular with radio manufacturers due to the mounting position and screening requirements.

The 2-pin base is the anode and screen grid connections, the anode being marked by a flange. The 3-pin base is the filament and control grid connections, the control grid being the middle of the three.