Sensibly equivalent¶ to:
The VT20 battery triode was designed as an audio output valve. With a maximum output of 190 mW it would be used with headphones and not a loudspeaker.
We have two versions of this exhibit, this one is the earlier of the two and is typically Cossor in shape and is fitted with a standard Cossor base cap of the mid-1930s. The later example of VT20 looks M-OV in shape, despite the Cossor marking, and is fitted with a standard M-OV base cap of WWII period.
The balloon envelope is 40 mm in diameter and, excluding the B4 base pins, is 84 mm tall.
References: Data-sheet & private communication. Type VT20 was first introduced in 1929.
Absolute Maximum Operating Conditions¶
Updated December03, 2012. shape:balloon construction:pinch type:triode age:1930.1940 base:b4 heater:2.0v pins:4 pin:1.a pin:2.g1 pin:3.f pin:4.f