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Marconi Radio Valve Type S625, by Marconi Company, England, c. 1928

Inventory Number: 49486

Number of documents: 2

Document Type: Miscellaneous Note

Document Heading: Technical Details


Captain HJ Round's S625 (first introduced in 1926) was a world landmark valve in that it was the first successful screen-grid valve to be used commercially in receiving sets and to merit quantity production. S625s were manufactured for several years and there are dozens of survivors, many in working order.

The S625 was a rare example of a screen-grid receiving valve with a thoriated tungsten filament, rather than a barium or oxide filament or cathode. In designing the S625 Captain Round used the standard filament and grid structure then used in the MOV Type DE5 triode, mounted sideways.

Document Type: Miscellaneous Note

Document Heading: Manufacturer Details


Marconi-Osram Valve Co. Ltd. was founded in 1919, and took over the manufacture of Marconi valves from Ediswan, the trade name of the Edison and Swan United Electric Light Company Limited. The M-OV, as it was later known, was a joint Marconi-GEC valve-manufacturing company. It produced all of its valves at the Osram Lamp Works at Hammersmith, London.

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