Power Tube Red Plating

Discussion in 'Marshall Amps' started by ken361, Sep 25, 2016.

  1. ken361

    ken361 Well-Known Member

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    I had these EH EL 34's for 8 months and starting to get that hum like the last set did so I replaced them. This hum wasn't as bad so I was trying to more mileage out of them. Today it seemed like it didn't have much sustain so I looked at the back of the amp and seen one red plating

    I don't have a meter yet should I recheck the bias maybe that will solve it or just order a new set of Rubys which I going to get next? Thanks!
     
  2. ampmadscientist

    ampmadscientist Well-Known Member

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    I wouldn't buy ruby tubes...sorry.

    But...reverse the tubes in the sockets....and test again.
    Now check to see that the problem IS(?) the tube (the same tube will red plate?)
    OR the problem IS(?) the socket....now the other tube red plates instead?

    Make sure it's the tube and not the socket first.
     
  3. Rick Lee

    Rick Lee Active Member Gold Supporting Member

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    I had it happen with a new pair of Chinese power tubes in my DSL 50. I had the amp dimed and was playing behind the head. One tube looked like it was full of lava and was about to burst. It blew a fuse and then cooled down.
     
  4. ken361

    ken361 Well-Known Member

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    OK will check thanks
     
  5. ken361

    ken361 Well-Known Member

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    Can I use one from my old Set same brand and rebias it? I have 2 bias pots
     
  6. ken361

    ken361 Well-Known Member

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    Yeah the tube is red plating after switching
     
  7. ampmadscientist

    ampmadscientist Well-Known Member

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    Yup, looks like you need tubes after-all then.

    Old tubes: try it...may still be good.
     
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  8. jlinde1973

    jlinde1973 Well-Known Member

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    Your dsl40c will have a hum..Couldn't get rid of it on my clean channel. Poorly made Vietnamese amp..sorry but it's the truth..had the same problems with mine. Shipped it.
     
  9. ken361

    ken361 Well-Known Member

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    It was the power tubes before and now that hummed, thinking the amps vibrations causes some issues down the line. I replaced on of my older tubes and biased it up last night
     
    Last edited: Sep 26, 2016

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