A SURVEY OF EARLY POWER TRANSISTORS

by Joe A. Knight

SYLVANIA 1950s GERMANIUM POWER TRANSISTORS

Sylvania, being a major supplier of vacuum tubes for car radio sets, was anxious to have power transistor product available to compete with the other device suppliers as this semiconductor conversion emerged for the 1956-1957 automobile models. One of the major design variations was the marketing of 'hybrid radios' with a tube front-end and a transistor output. This would allow many manufacturers to still brand their car radios as "Transistorized", and so the unsuspecting customer could feel they were purchasing the latest radio technology but without knowing exactly how much. Most car radios in these first couple of years were made like this. Given the advent of the type TO-3 design (specifically for car audio use) in 1955 Sylvania moved forward with the design of their own product, also sometime in 1955.

 

ABOVE, L-to-R: We know Sylvania was already dominating the Power Transistor market with their leading array of power devices produced through 1955. The basic Germanium alloy construction was pretty well refined by then. The next challenge was to work out a way of achieving a lot more power from this new flat mounted basing structure to be used in car radios. The first device shown, with the external aluminum cooling fins, is marked on top in hand-written pencil "Sylvania" as is the third item, which is unscrewed from it's element mounting base, the second item. Both marked items came from widely different sources but are in the same hand-writing, so can pretty well be taken at face value. The last item appears to be an adaptation of the previous style devices to a wide flat basing, similar to what Clevite was also doing with their CTP series about this same time, likely from late 1955 or early 1956. Note: While it can't always be appreciated in the photos, often times the genealogy of a manufacturer's series can be determined as much from viewing the bottom side construction as from as the top or insides. Usually, different manufacturers used their own unique part designs or part sources to achieve hermetic sealing of the exit leads and these would look the same or similar for a whole generation of output devices. While the differences can be small, they do help to distinguish and identify items not always marked in early pre-production periods.

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Joe A. Knight Early Power Transistor History SYLVANIA Page 4