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Making glass-to-metal seals for homemade vacuum tubes

64 points by zdw

by tyingq

0 subcomment

The research here is clearly interesting, but if you just need to get something like this working, premade neon tube electrodes are plentiful and inexpensive.

by alister

4 subcomments

What was the large-scale commercial procedure for making electrodes that pass through the glass without letting air in? I assume that electronics manufacturers must have been making millions of such vacuum tubes in the past. Is the knowledge lost (or not practical for hobby use)?

by projektfu

1 subcomments

I was wondering about the feasibilty of this, but I thought that useful tubes needed a harder vacuum than that. Is this really "good enough" for a triode?
I figured the wire-holding/element-holding aspect of a standard tube was in the base, and the glass-to-base seal is the important part. You can have a less-hot metal holding the filament and penetrating through the base. But I haven't looked carefully. These are my off-the-top-of-my-head thoughts about it.

by LgWoodenBadger

2 subcomments

Would you be able to reseal the cracked glass and regenerate the vacuum through the other end?
More glass, epoxy, or similar?

by smlacy

3 subcomments

Hmmmm. Wonder if you could just induct through the glass with coils on each side? Seems perfect for high voltage applications?