CHAMP ELECTRONICS -" THE VALVE AMP HOSPITAL"

NOTTINGHAM, ENGLAND

 

REPAIR OF A CARVIN LEGACY COMBO AMPLIFIER

 

 

 

 

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.

Your looking at the site is appreciated.

John.

 

 

 

 

 

 

 

 

 

 

 

 


 

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