Tubes Asylum

• Re: Biasing problem -- need advice - corerosin 21:02:04 03/21/05 (1)
  In Reply to: Biasing problem -- need advice posted by Scruffy_ on March 2, 2005 at 18:50:24:

  I once bought a five pack of new EL84 tubes and, of the five of them, three of them actually worked. Happily, these were new tubes and the vendor was a standup guy, so I was able to get replacement tubes. With used tubes you really don't know. It probably isn't the guy who sold them to you. You can never know which package looks like a bowling ball to some shipper; or looks like the bowling pin; or gets carried by the horse with three legs.
  
  

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  • Re: Biasing problem -- need advice - Scruffy_ 11:36:32 03/22/05 (0)
    In Reply to: Re: Biasing problem -- need advice posted by corerosin on March 21, 2005 at 21:02:04:

    I think in my case there's an actual problem with the amp because if I switch “good” tubes to the “bad” sockets I get the same results. Likewise the "bad" tubes begin to work great on the "good" sockets.

    I called Jolida, and much to my surprise, they said it was still under warranty and so I sent it back to them for repair. This is a unit I bought used, so I was surprised to learn it was less than 1.5 years old.
    
    

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• Re: Biasing problem -- need advice - MIchael Samra 19:07:52 03/20/05 (2)
  In Reply to: Biasing problem -- need advice posted by Scruffy_ on March 2, 2005 at 18:50:24:

  It is odd but not impossible.Swtich the tubes around with the tubes you cant bias with the ones you can bias and see what happens.Bias is pretty straight forward but what can happen and i have seen this more than once where you have circuit board mounted tube sockets, and when you take tubes in and out you break or weaken connections and you need to just resolder them many times.I would do this anyway becuase its so easy to do.Take your bottom off the amp and just touch up the connections where they dont look so good and especially on pin 3 of the el34s.
  
  

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  • Re: Biasing problem -- need advice forgot one thing - MIchael Samra 19:10:15 03/20/05 (1)
    In Reply to: Re: Biasing problem -- need advice posted by MIchael Samra on March 2, 2005 at 19:07:52:

    I meant to say all the pins on the sockets but especially pin 5 where the bias comes in at becuase im sure its negative biased.
    
    

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    • Re: Biasing problem -- need advice forgot one thing - Scruffy_ 05:33:23 03/21/05 (0)
      In Reply to: Re: Biasing problem -- need advice forgot one thing posted by MIchael Samra on March 2, 2005 at 19:10:15:

      Nice suggestion, but it did not fix it. Thanks!
      
      

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