If you have been playing with vacuum tubes long enough, you might have run into a situation that a new tube, shipped from a vendor, arrived with a piece of floating glass inside (see reference picture below). What is it? Where does it come from? Is the tube damaged beyond useful?
Here is the answer:
- This piece of floating glass is a broken-off piece from the tube filament glass stem. See picture below showing where it is exactly broken off from.
2. This broken piece is often resulted from the heavy filament structure in vibrating motion during shipping and handling. However, since the tube glass stem is a wide structure supporting the full filament structure – a small piece
broken off from the tip won’t hurt the tube structure’s integrity at all.
3. We see this ‘floating glass’ from TJ Full Music 300B tubes, but not much from other Chinese brand such as Shuguang 300B tubes produced in southern China. Our guess is that the glass supplier for Full Music (located in Northern China) is likely different and glass production technique isn’t exactly the same.
4. This piece of floating glass won’t affect tube function at all and won’t interfere with the vacuum capacity inside the tube. Glass is non-conductive. User only needs to stand the tube up, let the floating piece to fall to the bottom of the tube enclosure, plug the tube into socket vertically, then it is all done!