easy question (I think)

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by chitarriere1, Sep 28, 2003.

  1. chitarriere1

    chitarriere1 Guest

    Hi everyone,
    I've got a simple (I think) question to ask you: I need to re-tube my power-amp (a Marshall EL84 20/20), do I have to replace the other (3) tubes in it as well, or four new EL84s is everything I need (except re-biasing)?
    Thank you
     
  2. nateco

    nateco Member

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    If you are already retubing your power section,might as well change the others aswell.


    But you probably don't NEED to change them.
     
  3. Scott Peterson

    Scott Peterson Staff Member

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    You need to change out the entire power tube section; if you change one you should change them all.

    Properly matched tubes should have the same amount of use.

    You need to have your bias checked with new tubes too.

    You do NOT have to change out your preamp tubes though; they are good until they go bad and can last for decades in some instances.
     
  4. nateco

    nateco Member

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    Sorry,I thaught you ment changing pre amp tubes aswell as power tubes.
     
  5. chitarriere1

    chitarriere1 Guest

    Maybe I wasn't clear enough, but I think you both answered somehow. I will replace the four EL84s for sure, but there are three more tubes in that power-amp (one 12AU7 and two 12AX7 if I remember well), which I think are rectifier and/or preamp (but they still belong to the power-amp) tubes.
    So I can avoid changing those three "smaller" tubes, can't I?
     
  6. chitarriere1

    chitarriere1 Guest

    I've just checked at the Marshall website: the three "extra" tubes are one ECC82, which works as a pre-drive and two ECC83 which work as phase inverters. Do they need replacement?
     
  7. nateco

    nateco Member

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    Correct,you do not need to change the other tubes(12ax7,12au7).Those are phase inverter tubes,I think.
     
  8. chitarriere1

    chitarriere1 Guest

    Thank you, that was I hoped you said! (This way retubing will be cheaper...!)
     

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