by mesherm » Fri Apr 11, 2008 2:11 pm
The getter is actually the small ring or pan that holds a bit of barium. After the tube is evacuated and sealed, the getter is heated up by induction to vaporize the barium which then condenses on the inside of the glass. The slightest air leak will oxidize the barium into a white powder. I haven't seen any tubes with those pinholes but I have seen tubes where the barium is thin and almost see through. There might have been some coating or cleaning substance left on the inside of the glass during manufacture that caused an adhesion problem with the barium vapors. That or they were skimping on the amount of barium they used. If you rotate the tube around do you see any tiny particles rolling around inside? 6p14ps are not that expensive, I would be just replace it.
Mike's N-1 Rule: When looking for N number of components to finish a job, you have a 95% chance of only finding N-1 of them.