Blew an EL34, I think

I was doing some room frequency response testing, sweeping from 0 Hz all the way up to 20k, and my amp, a Jolida 1000p, was holding up just fine. At some point, the AC kicked on downstairs, the voltage dropped, and the amp shut off. It's done that before, so I just pressed the button again. Every time it applied voltage to the plates, it shut off immediately. I took out each tube individually until I found that the tube in the V10 position was the culprit. It doesn't look any different to the other ones, or rattle, or show any visible problem. I'm going to put this tube in my Marshall amp tomorrow and see if I can observe what it looks like when it has voltage running through the plate - or perhaps I'll blow a fuse in the process. The Jolida amp doesn't allow voltage to run wild through its tubes; it has a protection circuit, so I imagine it's just a bad tube. I hope I can get a replacement.

Tube amps and vintage NOS tubes are fun, they all said!

 

Nic power amp ! I am about to start my tube journey.

 

I briefly placed the affected tube in my JTM45 clone this morning, paired with another of my EL34s, which runs God knows how much voltage across the plates, and both channels were working fine. I put them back in the Jolida and the amp is now working just fine, for now! I'm not sure what that was about. Maybe it needed a few seconds for the voltage to stabilize, and the Jolida amp wasn't letting it?