[Milsurplus] How Much Vacuum in "Vacuum Tubes?"

[J Forster]

  I read a number of articles in old (early 20s and before) radio
  magazines about amateurs making their own tubes. I have a tube in my
  pile of stuff that looks very crude and crooked inside, not sure if it

  could qualify as 'homemade', though.

  Maybe it gets down to losing skills due to progress and cost? If you
  can buy a new one cheaper, why go through the hassle and all that.

  ~ Todd,  KA1KAQ


Making tubes is not that hard. The first ones were made with the
technology of roughly 100 years ago. If you can work small pieces of
thin metal, blow glass, and pull a vacuum, you can likely make a decent
tube. Getting them to perform better and be consistent takes more
effort, but obviously can b done.

IMO, it may be easier to build a simple tube from scratch than repairing
one with a bad filament. Before my time, MIT used to teach a 'Tube Lab'
. They published a set of notes on how to do it which make interesting
reading.

Making tubes is certainly practical in a small facility. Not so for
transistors or ICs.

-John