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ORA

 
See also:
Mullard R & ORA Advert - Mullard HF, LF, WECO, ORA & DF.ORA Advert - Mullard ORA Advert - Mullard ORA Advert - Mullard ORA Advert - Mullard ORA Advert - Which Valve Shall I Buy?
    
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This version of the ORA from Mullard was designed in 1923 and the original tubular envelope of the original design ORA has given way to balloon envelope.
The Mullard label on the valve can be seen in this picture taken against a dark background.
The other side of the valve shows the ORA logo. The ORA stands for Oscillator, Rectifier, and Amplifier - its planed usages.
In close-up the detail is revealed. It shows an aerial symbol joined to a coil symbol and finally ending with the ground symbol. The general purpose valve able to do any job in radio.
The ORA is a bright emitter valve and had a μ (amplification factor) of 8.5
In construction, the valve has a metal skirt and the familiar tubular anode. The grid is held in a pair of twisted wires and is formed by folding the grid wire in to a square wave shape and then bending the result into an open cylinder.
See ORA for a wire helix grid. The filament is a single strand of tungsten wire, tensioned by the support arm.
The thin glass tube envelope is 24 mm in diameter, and excluding the B4 base pins, is 83 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 May 20, 2015.
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