In article ,
"Martin H. Eastburn" wrote:

I taught Tube design (circuit) and later, taught EE's who knew tubes
solid state. So I had to know both designs and show relationships.

Eimac was the maker of Power transmitting tubes. I think of pyramid tubes
and potato sized kilowatt transmitting rubes. TV and Radio as well as
military used them. I think I have one or two in the shop. They used
to advertise in ELECTRONICS magazine in the 50's. Those were the years.

The years of the 807 and 6146, 12A7, etc. etc?