The Three-in-One is an early multiple valve. The Quadruple Valve Co made two types of valve in 1929 - three triodes and four triodes in one envelope. This exhibit was incorrectly marked as the four triode version by a previous owner.
The gettering hides almost everything except the pinch stem.
The 12 base pins with copper wires wrapped round the pins and soldered.
Looking up from the base shows the pinch and one horizontal tubular triode.
Here the triodes can be seen to be mounted in the form of a triode. The filaments are single strands passing through the centre of the cylindrical anode.
The triode on the right has a single sided grid support.
The three triodes.
This micrograph shows the structure of one triode. The filament is oxide coated and the grid is a helix with a single side support.
One of the filament fixings. Here the wire is seen before the start of the oxide coating. The fixing is two part and closed together. The wire looks to be welded to the first support and so is probably not tungsten.
The balloon envelope is 54 mm in diameter and, excluding the 12 base pins, is 108 mm tall.
References: Data & 1043. Type Three-in-One was first introduced in 1929. See also1929 adverts.
