Octavarius
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- Jul 31, 2006
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Ok, so today I finally got a chance to crank up my IIC+ really loud, and after some time, I noticed that the far right EL34 was glowing red hot, (yes, only that one) and there was some humming noise coming through the speaker. I shut it off, then the fuse blew. So I changed the fuse and turned it on again, and everything was fine, but the blue lights on that tube weren't glowing the same way as in the other EL34 (neither as they used to glow before). I could see a blue light being turned on inside the plate as I flicked the standby switch, but the blue lights usually also light through the "holes" in the plate, if you know what I mean. And now they weren't.
So I put in a new tube to diagnose further, and it worked fine for a while (with the blue lights glowing normally), then at some point, when switching from Class A to Simul-Class, this one started red plating too. This time there was some serious "lighting" inside. Bright white and blue lighting and then fading into a bright red glow. I flicked the standby switch on and off, and it was doing the same thing again (squealing noises coming too through the speaker). I turned the amp on standby for a little longer, and the the tube was fine. But again, the blue lights weren't glowing as bright, and I noticed that the clean channel was going into overdrive unusually soon (4 and higher at Volume 1) I seem to remember that it had much more headroom before going into overdrive before this happened.
Then I switched places with the other EL34 on the other side, and the blue lights glowed bright as before (although a bit weaker on the tube that had red plated (now on the other side)) And so far the amp is fine, but I feel that it's only a matter of time before the good tube starts red plating.
Obviously, it couldn't have been bad tubes, right? (two brand new ones in a row?) So I guess there's something in the amp that's causing this. So how could I diagnose this further? What should I check? Bias caps?
And, the issue with the blue lights almost not glowing (or glowing differently, as I described before), does that mean the tube is dead? Could that be the cause of early overdrive?
Please help me out here.
So I put in a new tube to diagnose further, and it worked fine for a while (with the blue lights glowing normally), then at some point, when switching from Class A to Simul-Class, this one started red plating too. This time there was some serious "lighting" inside. Bright white and blue lighting and then fading into a bright red glow. I flicked the standby switch on and off, and it was doing the same thing again (squealing noises coming too through the speaker). I turned the amp on standby for a little longer, and the the tube was fine. But again, the blue lights weren't glowing as bright, and I noticed that the clean channel was going into overdrive unusually soon (4 and higher at Volume 1) I seem to remember that it had much more headroom before going into overdrive before this happened.
Then I switched places with the other EL34 on the other side, and the blue lights glowed bright as before (although a bit weaker on the tube that had red plated (now on the other side)) And so far the amp is fine, but I feel that it's only a matter of time before the good tube starts red plating.
Obviously, it couldn't have been bad tubes, right? (two brand new ones in a row?) So I guess there's something in the amp that's causing this. So how could I diagnose this further? What should I check? Bias caps?
And, the issue with the blue lights almost not glowing (or glowing differently, as I described before), does that mean the tube is dead? Could that be the cause of early overdrive?
Please help me out here.
