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Okay, folks, here is another one to add to our "collective experience".
Another VK member needed the safety glass off of a 21FJP22. Since I had a couple dud tubes in the attic I decided to pull one off. The crt in question is a used Philco-built tube that was gassy, from all I could tell. Certainly beyond anything a rejuvanator could do. I took it took work and let it sit in the shop for a few days before deciding to work on it today. I started warming it up with the heat gun-I've done 4 or 5 of these before using this method but after reading a couple implosion stories, I found myself unerved this time. I decided it really made more sense to air down this tube. I used my usual method for tubes I'm going to junk-I used an awl to poke a small hole in the ultor. No drama, it went to air in a minute like they usually do. I then flipped the tube back over. I decided instead of using the heat gun I would use a bank of infared lights I have at work. After setting them up it took some time before I started seeing results, maybe 45 minutes or so. I rotated it 30 degrees or so every time I walked by. At one point I looked and saw cracks, which made me think the safety glass had broken, but on further inspection I saw it to be the PVA. It was not until later, when the glass loosened enough to pull off, that I realized that, in fact, the face of the crt had cracked! (see photos) I can only assume this would have also happened had I not aired the tube, in which case I would have woke everybody in the shop up!
Lesson for me: from now on, it will be water only. I just don't trust heat anymore.
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Bryan
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