Tim -
there's a lot more to it than how strong of a vacuum was pulled. Cathode coating mix, design, manufacturing skills, many tricks of the trade that are now long lost forever. All of these contribute to the difference between NOS tubes and current manufacture. I was an unbeliever initially until I tried old tubes for the first time. Now I have thousands of them.
-Ed
there's a lot more to it than how strong of a vacuum was pulled. Cathode coating mix, design, manufacturing skills, many tricks of the trade that are now long lost forever. All of these contribute to the difference between NOS tubes and current manufacture. I was an unbeliever initially until I tried old tubes for the first time. Now I have thousands of them.
-Ed