On Sunday, June 2, 2019 at 7:48:36 PM UTC-4, Cursitor Doom wrote:
I didn't know people still do this...

https://www.youtube.com/watch?v=dRI0ZLTP6_0

Yes, they do...the fellow here is extremely talented...even produced curves for his tubes.
https://www.youtube.com/watch?v=EzyXMEpq4qw

I lived not very far from the Sylvania tube factory in Pennsylvania. Quite a few articles on the net about it and the physics and metallurgy that went into designing and fabricating high quality electron tubes. It was generally acknowledged that Sylvania tubes equaled or surpassed RCA tubes in quality and long-life.

In a wild day dream one week I did quite a bit of searching of what it would take to create a high quality tube factory equal to what sylvania had. To actually put the equipment in place and the associated know how. It seemed to me that a lot of the 'art' (craftsmanship) has been lost and would need to be relearned, thus making a business endeavor extremely risky. It also seemed that some of the underlying physics/chemistry/metallurgy would have to be rediscovered. That put it out of my scope of knowledge.

I can see an ad in IEEE spectrum: Wanted - electronics engineer/physicist experienced in electronic vacuum tube design and fabrication. Don't think I'd get many takers.
Looks like will have to subsist on Russian and Chinese 'knock-offs'...
Well, it was a nice dream...