[AMRadio] 4-400 first made when?

[John Lawson]

   In doing some research - I notice that the 4-400 seems to be a fairly 
late arrival, at least as far as RCA is concerned. It's in none of my 
HB-3s, not in my 1962 TT5, but is in the 1975 TT5 manual.   Since my 
transmitting tube library has this 12-year gap, I'm assuming RCA began to 
produce the device sometime after 1964... does anyone have better info on 
the history and development of this very 'popular' power tube?

   Thanks in advance for any enlightenment!

Okay - over and out...



Cheers

John
KB6SCO
DM09fg