We see quite a bit of work where people decapsulate ICs or other solid state devices to expose their inner workings. But how about hollow state? [Tomtektest] had a dual triode that has lost its vacuum integrity — gone to air, as he calls it — and decided to open it up to better expose its inner workings. (Video, embedded below.)
Of course, you can always see the innards through the glass, but it is interesting to have the envelope out of the way. Apparently, how you remove the glass is a bit tricky if you don’t want to damage the working bits as you remove it.
It was interesting to see that the elements of the tube were clearly separate as you might expect in a dual triode. However, one of the subtubes is much smaller than the other. [Tom] shows on the datasheet that the two triodes have very different specifications. The smaller one was typically used as an oscillator and the larger one was often used as an amplifier.