by Joe Knight




Next up is the CBS line. They were quite an early developer in the transistor world having come out with their own products in 1953 right when RCA and GE came out with their first items, ala the 2N36, -37, and -38. So it was only natural to expect them to be in the forefront of power transistor design - and they were.


In late 1954/early 1955 CBS had released a small power transistor called the HD-197 (HD for Heavy Duty?? - a common nomenclature), which was rated at 1/2 watt dissipation. This was their first venture into power output devices. This shows up in 1955 listings but I have seen no example. They later released another pair called the HD-337 and HD-369, likely later in 1955. The HD series probably all looked similar to the CBS 2N156 type, shown in page 2.



TOP ROW, L-to-R: In early 1956, CBS came out with the very first TO-3 type high power transistor. This was the 2N155, far left and middle. I believe later in 1956, the 2N157 (and 2N157A), far right, was released. This one never seemed to get any promotion or advertising like all their other products did. These were all Germanium PNP types and rated at 8.5 watts dissipation.



BOTTOM ROW, L-TO-R: Later in 1956, CBS brought out some additional TO-3 types, the 2N255, and 2N256, far left and middle. These were more conservatively rated at 6.25 watts dissipation. They also came out with a TO-3 "DT" series, such as the DT-62, far right. Not sure what the DT stands for.




Go To CBS Early Power Transistors, Page 2





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Joe Knight Early Power Transistor History CBS