WN3-14

Philips early developmental sample of all-glass receiving tubes, later originating the B9G lock-in family. The sample has a rimmed spigot and nine pins, bented to lock the tube in the socket with a small rotation. Internal costruction visible from the clear glass envelope shows the presence of a diode mounted side-by-side to a four grid amplifier.

Jacob Roschy suggests this sample could be an early prototype of the DAH50. Actually it looks very similar, but for the apparent absence of the first beam-forming grid. Jacob also gives a conclusive explanation for the apparent involution from the all-glass prototype to the octal-based production type. In May 1940 the entire new line for manufacturing B9G tubes was hastily moved from Eindhoven to England just before German troops invaded Holland. Subsequently productions of the newly developed tubes in Holland had to be switched to types, as the octal-based ones, that could be handled by the old manufacturing lines.

The early development of B9G all-glass tubes can be read at the page:

The EF50, the Tube that helped to Win the War

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