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ORA

 
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Some Important British Valves - Which Valve Shall I Buy?
    
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The ORA from Mullard was designed in 1922 as a development of the K valve and the redesign was prompted by the commencement of broadcasting. This exhibit is one of the early samples as later production had a balloon envelope.
This valve does not carry the Mullard name but that of Gamages - a well known and respected London department store of the day. The store was well-known for its unrivalled selection of children's toys. It finally closed in 1972, and no trace of the original buildings remain.
The Gamage name logo etched into the glass.
The ORA logo with aerial-coil-earth symbol.
The logo enhanced.
The filament is a single vertical strand. The grid wire is folded into a series of loops. The folded wire has then been laced to the support wire that runs vertically with the grid.
The Gamages store in Holborn. Image courtesy Londonist.com
The thin glass tube envelope is 25 mm in diameter, and excluding the B4 base pins, is 82 mm tall.
Reference: 1003. Type ORA was first introduced in 1922.

 

Pin Connections
B4
1
2
3
4
a
g1
f
f

 

Absolute Maximum Operating Conditions
Triode
Vh
Ah
Va
ra
gm
3.8
0.65
30-90
27,000
0.32
Updated September 28, 2017.
shape:thin.glass.tube construction:pinch type:triode age:1920.1930 base:b4 pins:4 pin:1.a pin:2.g1 pin:3.f pin:4.f
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