Tube or Amp Problem? Please help.


I have a Melody El34 Integrated Amp that I use with 2 pairs of Shuguang Treasure 6CA7-z. Last week I was listening to music when everything went all horrible sounding and one of the tubes lit up like blue fireworks. I turned off the amp and looked at it the next day. To my, admittedly untrained eye, the tube looks fine but when I checked the bias it was at .32 (the amp says to set to .40) so I tried to set it to .40 but it would only go to .34. All of the other tubes I can set to .40. I have never had this issue with this amp. Is it the tube or did something happen to the amp? If it's just the tube will it be ok to have one set to .34 and the other .4 or should I set both tubes to .34, all 4? I would buy a new pair but they were expensive and on top of that don't seem to be offered anymore.

128x128jkontuly

Bigkidz thanks for the kind offer. I used to live in Brooklyn. If i still did I would definitely take you up on your offer but I know live in LA which is a bit too far!

 

gs5556, I was able to find some spare tubes. I put them in and was able to reduce the bias for the tube location that had the fireworks. Hopefully, that means it was just the tube and not the amp, correct?

 

 

@jkontuly if the bias pot had range when turning left and right, then the amp is ok. However, you want to make sure that bias will remain steady and not drift.

Given that I can set the bias for each tube individually is it still important that I replace both on the side that this occurs...I still plan on doing this but just more for my own education.

Given that I can set the bias for each tube individually is it still important that I replace both on the side that this occurs

Although the bias is independent the circuit is designed to have a pair of matched tubes.