I thought this might help someone. A couple of weeks ago I got this sweet 12aT7 Mullard old tube. The guy who gave it to me tested it before in front of me and it was just fine. I put it in V5 which is responsible for the reverb and I noticed a slightly warmer reverb, as someone suggested. It was subtle but I decided to keep it in.
Today the amp started sounding thin, or the volume would slowly fade away to very quiet in a matter of 10 seconds and it was very gradual. But it would happen only after being played for 20 minutes or so. So I checked and all the tubes were lighting up and in their sockets.
I also tried with V1 by pulling out and back in, everything seemed ok for a bit. Then it happened again. I switched out the Mullard and the amp seemed to be working ok. so out of curiosity I put back the Mullard and after 10 minutes, bang again. I take it out and put it back in the EH and the amp works fine.
Then I look at the mullard and I noticed the ring filament on top that wobbles around.
How is it possible that a broken tube would make the amp work fine for 20 minutes and then I guess pass out due to warming up? Is it possible that an excessive voltage killed this Mullard? Usually old pre-amp tubes last forever? it was lighting up and it was just a regular orange color.
I'd like to hear some opinions?
Today the amp started sounding thin, or the volume would slowly fade away to very quiet in a matter of 10 seconds and it was very gradual. But it would happen only after being played for 20 minutes or so. So I checked and all the tubes were lighting up and in their sockets.
I also tried with V1 by pulling out and back in, everything seemed ok for a bit. Then it happened again. I switched out the Mullard and the amp seemed to be working ok. so out of curiosity I put back the Mullard and after 10 minutes, bang again. I take it out and put it back in the EH and the amp works fine.
Then I look at the mullard and I noticed the ring filament on top that wobbles around.
How is it possible that a broken tube would make the amp work fine for 20 minutes and then I guess pass out due to warming up? Is it possible that an excessive voltage killed this Mullard? Usually old pre-amp tubes last forever? it was lighting up and it was just a regular orange color.
I'd like to hear some opinions?
