Conserving our good CRT's

[jr_tech]

Originally Posted by Tubejunke

I have never heard this before. Now it is common knowledge that some of the early metal/glass tubes (19AP4) developed leaks over the course of many years, but I am compelled to ask the basis behind all vacuum tubes leaking when there are so many around from the 40s-60s that are as strong and void of air or gas as they were when new.

If they do leak, then it must be immeasurably slow. Too slow for our lifetime. My 1920s radio tubes (O1A and the like) are holding up well too. This might be an interesting topic.

My major point was that the barium deposited by the getter flash continues to function to remove gas in a sealed off CRT for many years after it is flashed. There are several sources of this gas.
1. Incomplete processing... some surfaces may still be outgassing.
2. Virtual leak... gas trapped in very fine porosity of the CRT materials that may come out.
3. Real leaks... such as around base pins, tip off seal, frit joints.

Indeed, with decent techniques these are very small sources of gas...but get back to me in 100 years or so about the condition of your tubes.

jr