Did I break my tube? (new blue glow)
I was swapping tubes in my amp, and dropped a 307a(vt-225) a foot or two. It was still in its box and bubble wrap. When I opened it, the metal plate cap was off. The wire inside still fine. I was able to scrape off some dried glue and push the cap back on. It seems to have made a solid contact. I put it in and biased up the tubes.
All sounds great, bias stable. But, the tube I dropped has blue glow around the top.. right where the glass restricts at the top.
I've seen other tubes that were fine glow this much.. But the fact it didn't glow before has me concerned.
so basically, did I break it, or is it possible things got a little misaligned when it fell, so new sections of glass are being struck by electrons? (maybe the plate slid down a bit, or something.. I'm just guessing, hoping I didn't kill my tube..)
If I did somehow break it, what's the likely failure mode? Basically, can I use it until it dies or glows to a disturbing level, or should I just remove it to keep my amp safe?
Thanks for any advice.