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Bi-Grille

 
See also:
The Bi-grid Valve
    
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The Fotos Bi-Grille is a bi-grid valve from the 1920's. The French Fotos company produced some of the earliest hard vacuum valves.
The special five pin base is larger than the standard B5 base. The anode is the centre pin, with pins 1 & 2 as the grids.
The electrode system is mounted horizontally above the pinch. The filament is a single strand and the grids are concentric helixes.
The right hand side of this image shows the inner grid and the start of the outer grid helix.
The right hand side of this enhanced image shows the inner grid and the start of the outer grid helix slightly clearer.
The wide glass tube envelope is 39 mm in diameter, and excluding the special base pins is 89 mm tall.
Reference: 3002. Type Bi-Grille was first introduced in 1925.

 

Pin Connections
1
2
3
4
5
g1
g2
f
f
a

 

Absolute Maximum Operating Conditions
Triode
Vh
Ah
4.0
0.08
Updated May 01, 2013.
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