This Carmen Legacy 212 came through the workshop with the simple fault of randomly reducing in power and output.As most modern amps are nowadays, she was also on circuit board(s). A badly connecting effects in-out jack socket which was causing the problem was soon sorted, and the customer was very happy to have it back and pleased with the results. However, after only a week, the amp was back in the workshop with a different fault! This time, all four of the EL34's were going into meltdown; glowing like an electric fire-bar element, and again at random!
I knew full-well that this was a negative bias problem, i.e the bias was disappearing for some reason, and also when fixing the original fault I had checked and re-biased the output tubes anyway as part of a normal service/check-up. It therefore seemed logical that, as I had disturbed the bias pre-set potentiometer, this could be the cause of the new fault.On investigating the problem, it turned out that my suspicions were correct. The pre-set potentiometer was "iffy", and was causing the bias to be removed from the output bottles! After the replacement of the original bias pot with a much better quality and accurate 20-turn Cermet pot, the problem was gone.
Antonello (or Anton for short) has used the amp over the 2006 festive period with a mish-mosh of old EL34's that I put in just to tide him over, and to be sure we had found the problem. His four Electro-Harmonix EL34's were well down anyway and probably damaged due to the lack of bias, which would not really have done them much good! Either way, the Electro-Harmonix EL34's are junk anyway. (That's only my opinion of course!) Anton is going to bring the amp back soon, and I will install and bias a new matched set of JJ EL34's. These are the best new modern tubes out there by far!!
As for the Carvin itself, it is a nice amplifier; very well built, solid, and sounds great, but it is one hell of a heavy mother of an amp! By the way, it's very unusual and rare to find a combo with a completely closed in back on the speakers, as is the case with this model. However, she does sound great, with lots of balls!..........A nice amp.
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