A SURVEY OF EARLY POWER TRANSISTORS

by Joe A. Knight

SYLVANIA 1950s GERMANIUM POWER TRANSISTORS

ABOVE, L-to-R: These first 'new' Sylvania 2N68s were uniquely different from the more common later ones you might find today. The first item, the "2N68", shows the early device lettering was colored a slight beige/gold and some may also have a date-code printed on top. The second cut-open item shows that the semiconductor elements were mounted onto a copper slug and sealed around with an obsidian-like resin inside the aluminum cooling fin cavity. All these new devices were now rated at 2.5 watts of dissipated power in free air but did use rather small flexible wire leads compared to later versions. The third item, the Sylvania "GT 545", is typical of other companies that used an 'in-house' numbering system for products used internally and is I believe a version of the 2N68. The last item, the "GT 551", is a likely 'in-house' version of the later 2N95, shown below. On the top (around the leads) can be seen the resin sealant, which was used in different colors, although it is not known if this has any technical significance. Not shown would be an early "2N95" power transistor (an NPN equivalent) which is electrically and physically identical to these shown.

ABOVE, L-to-R: The above photo shows the early 'thin-wire' Sylvania types, 2N68, 2N95, 2N101 and 2N102, from early 1955. These were all constructed with the resin insulated center where the junction elements and leads are located, mounted on a copper slug. These just released 2N101 (PNP) and 2N102 (NPN) types do not have the later steel shell enclosed construction (see page 3, bottom photo). As we now know these two were constructed basically the same as the 2N68 (PNP) and 2N95 (NPN) types but without the aluminum radiating fins, and were not long in production (few, if any, have survived) as the new higher gain versions of all types came out by mid-1955 (see next page).

Go To Sylvania Early Power Transistors, Page 3

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Joe A. Knight Early Power Transistor History SYLVANIA Page 2