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L610

Sensibly equivalent to:
CV3538
See also:
The Azide Process
    
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The L610 is an early example of an audio output valve designed to drive a loudspeaker in a domestic radio receiver. It dates from 1929 and was for battery operation.
This specimen was manufactured for professional use (NB. MWTCo label & logo) during the later 1930s. The Marconi Company (then MWTCo.) favoured 6V filaments (large cathode area, lots of emission, longer life) for many purposes long after the domestic market had moved to the more economical 2V series. In particular, battery-operated low-impedance types such as the L610 were used in stable, low-drift RF oscillators for driving broadcasting transmitters and similar high-quality equipment.
The L610 was the lineal descendent of a series of similar valves including the DEL612 (thoriated tungsten filament) and the DEH610 (barium-coated filaments using the azide process). Interestingly, although this exhibit definitely has oxide-coated filaments and was not made using the azide process, its micaless construction is an anachronistic hang-over from the azide era.
The balloon envelope is 43 mm in diameter and, excluding the B4 base pins, is 90 mm tall.
References: Datasheet & 1043. Type L610 was first introduced in 1929.

 

Absolute Maximum Operating Conditions
Triode
Vh
Ah
Va
Vg
mAa
ra
gm
Pout
6.0
0.1
150
-9
9.5
3,500
2.3
0.07W
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated February 03, 2013.
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