I recently got my hands on a huge(-ish) job lot of mostly German tubes from some attic-find or whatever. As i was sorting through them, in order to take inventory of what's what, i noticed a minority of them (of various types) seem to have developed shiny spots or an entire shiny coating around the mid-height area of the tube. I doubt it's a sign of loss-of-vacuum, since the getters at the top of said tubes are still shiny themselves, but they still don't inspire all that much confidence.
Can any of you greybeards (and i mean that with the utmost respect experience-wise, anyway) shed light on this? I haven't dealt all that much with used / old tubes, so i'm not quite sure what to make of it myself.
Can any of you greybeards (and i mean that with the utmost respect experience-wise, anyway) shed light on this? I haven't dealt all that much with used / old tubes, so i'm not quite sure what to make of it myself.