This is an amazing video – hand-made vacuum tubes! About 17 minutes long – well worth the watching if you have any interest at all in old equipment!
https://vimeo.com/47812871
Enjoy!
Robert Gulley, AK3Q, is the author of this post and a regular contributor to the SWLing Post. Robert also blogs at All Things Radio.
Can he make an rca long black plate style 12ax7 tube with a gain factor of 200%?
Just a guess, of course, but considering the vast machine shop to which he has access or owns, and the usual precision of good equipment, I would expect his tubes to be of very good quality. Or perhaps I am just easily impressed! I cannot get over the time all of this must take even when using some of the machining tools he has – what we don’t see in the video is the setup of such tools. From my woodworking/woodturning experiences, the setup to achieve a desired result often takes far longer than doing the actual cut or shaping, etc.
My question is what is the quality like. When valves started to be made by machine at least they were able to control the quality and each tube would be the same. I know someone who recently paid lots of money for hand-made tube for his hi-fi unit. Both and left channels should be the same. But you can tell the difference.
Surely it depend on who makes them.
In 1964, or 65, QST ran an article by or about an Argentinian who made tubes. Such things are forgotten in an age when people look no further than the latest viral video. But he didn’t build common tubes, he built transmitting tubes. Maybe those are easier to make since being power tubes, things have to be bigger. If I recall properly, he built some copies if exiting tubes, but was more interested in making his own. So that required not just having the “crafting” skills to make tubes, but know enough to understand the internals. I suspect people made their own tubes in the early days of radio, but I’ve never seen any articles. But perhaps there were, that would like provide some insight. You’d probably make some tubes, learn from that, and make more.
Robert Heinlein in his sf book “Rocket Ship Galileo”, had one of the characters get all excited once on the moon, realizing in the vacuum of space that he could more easily make tubes. I wonder if that was practical, or if dust would get in the way. But it has the advantage of allowing breadboarding , build a tube but everything accessible since you didn’t need to seal it in a glass tube.
Michael
How well do they work?
AMAZING!