by Joe A. Knight




As we know from our tube history, Amperex was owned by and the U.S. distributor for the Dutch manufacturer Philips.  In the continental Europe their products were marketed under the Valvo name. In England they were sold under the Mullard name, but still the same items with matching factory and date codes.  As such they provided many items made in Holland to the U.S. market besides the number of items already made in the U.S., such as their larger transmitting tubes. In late 1954 Philips brought out the OC-72 PNP Germanium alloy audio output transistor and then in 1955 the 2-OC72 (top row, left pair), a matched pair (MP) for push-pull class B output.  The matched pairs would have red dots on them apparently to help identify matching characteristics.  These were announced into the U.S. also in 1955 and were identical to the Valvo/Mullard types so were likely made in Holland too.  The 2-OC72 was rated at .25 watt output, MP.  Later they were distributed with an attached copper cooling fin (top row, right) and rated at 1/3 watt output, P-P.  Then, in 1956, apparently in an effort to give their transistor line better adaptability in the U.S. market, Amperex registered their transistors with JETEC and the 2-OC72 became the 2N282, a matched pair of individual 2N281's, the OC-72 equivalent. The 2N282 came standard with the copper cooling fin. The whole  Amperex 2N279-2N284 line was short lived apparently because by 1956 most other U.S. manufacturers had moved far beyond the power and frequency range of these types. As such, finding any early Amperex marked types is quite challenging.


In early 1955, Philips came out with their first production large power transistor, a PNP Germanium alloy type (bottom row).  In the Valvo line it was called the 100. O.C. (picture in 1955 German book, “Der Transistor” by J. Dosse).  In the English Mullard line it was called the "OC 15".  And in the U.S. it was identified as the Amperex "2N115" (see photo).  The pre-production samples shown above were all directly from the Holland factory as they all are tagged "100. O.C." and marked with European style handwriting. As such these were likely some of the first ones of this version. Each one has a different serial number, such as the middle item above, No.  1048.6, shown with it's own spec sheet, also in European style handwriting.  This transistor was rated at 3 watts dissipation and at 5 watts class B output, push-pull.



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Joe A. Knight Early Power Transistor History – AMPEREX