I’ve used two pairs of the new WE 300Bs in my Elekit TU-8600S and have had no issues, just absolutely unmatched wonderful sound quality.
I would be amazed if they didn’t give you a prompt warranty replacement.
Western Electric 300B problem
So I recently purchased pair of WE300B, Friday night first listen. At start up heard mechanical pinging and popping, pre muted so nothing through speakers, after the pinging and popping ended, pre out of mute heard nothing unusual through speakers. No issues other than blue glow at tops of tube throughout 5 hour listening session. Tonight I power up tubes for second listen, immediately see left monoblock tube goes completely cloudy with blue fog throughout tube, this along with popping, right monoblock tube fine.
So it seems I have gassy tube, lost vacuum already! And here I thought recent improvements with quality control there had solved these issues. Not happy with this purchase, been running Psvane Acme 300B's for nearly 1000 hours with no issues.