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ID = 28908
Great Britain (UK)
Brand: GEC, General Electric Co.; London
Tube type:  Triode, vacuum   Power/Output 
  <1925 very rare. ***
Identical to VT25_GPO = CV1637 = LS5_GE

Base UV-Base (4 Pins+Bayonet, USA 1914 WE)
Was used by Telephony
Filament Vf 4.5 Volts / If 0.82 Ampere / Direct / Battery =

The telephone network in Great Britain continued to grow. By 1926 there were twenty-six repeater stations with total of 670 repeaters in service. One of the standard amplifying valve used in such repeaters, designed by the Post Office as "Valve Thermionic (VT) No. 25. It was made by General Electric Company Ltd., London and was a further development of the R valve used in radio applications. It was used in radio receivers as an output valve under the designation LS5. Early versions of this tube (page 368, Tyne) show a tipped tube with what would be an American "Shaw" base. The tubes did use genuine "Shaw" bases imported to the UK by the MOV Works and these are actually branded "Shaw". Later tipless versions of the VT 25 had a polished nickel plated Shaw style of base but it is not known if these were American made or made by MOV. Filament voltage 4.5, folament current .82 amps.

Dimensions (WHD)
incl. pins / tip
x 125 x 57 mm / x 4.92 x 2.24 inch
Weight 54 g / 1.90 oz
Information source Saga of the Vacuum Tube, Tyne   page 367, 368
British Radio Valves - The Vintage Years, Thrower   pages 84 and 133
VT25_GPO: Jeremy Harmer collection
Fin Stewart


from Just Qvigstad

Forum contributions about this tube
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Fin Stewart

The original version of the VT25 had an American made "Shaw" Navy metal shell UV base with the Shaw logo of an "S " inside a diamond stamped into the base within the pin area. These tubes were tipped. Later tipless versions, c. 1930, had a metal shell Shaw base which was polished nickel plated. The VT39 and VT40 tubes, similar to the later VT25 were also fitted with the polished Shaw base. 

End of forum contributions about this tube

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