On Mon, 27 Feb 2017 16:38:10 -0600, wrote:

I have yet to find a decent chart which explains the reason for the
numbers/letters used on tubes. (For USA tubes).

I don't have an answer to your question. However, note that any
significant numbering scheme always falls apart as technical progress
advances faster than letters and numbers can be contrived to match.
For example, we started with 1Nxxxx = Diode, 2Nxxxx = Triode (BJT,
FET), 3Nxxxx = (Dual gate MOSFET), 4N = Optoisolator, etc. That
lasted about 10 years before devices arrived that could not easily be
crammed into the significant numbering scheme. The JEDEC would have
been better off just starting at 00001 and counting up in sequence. It
would seem that the semiconductor people had not learned the lessons
of tube numbering, and repeated the basic mistakes.



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Jeff Liebermann
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