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Peavey Classic 30- TUbe IssUes?

Discussion in 'Amp Central Station' started by jamsam95, May 9, 2020.

  1. jamsam95

    jamsam95 NEW MEMBER!

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    Hi everyone!

    so I have a Peavey Classic 30- it’s a beautiful amp, with a super lush and warm sound- but recently it’s been making these godawful sounds. It works fine for about 5 minutes then begins to screech and scream. I think my tubes need replacing but I’m completely ignorant when it comes to amps so would appreciate some guidance! How would I go about locating the source of the problem? How do I know if my tubes need replacing, and if so which ones? Preamp or power tunes? Etc etc.

    the screeches and sounds aren’t affected by how loud the amp is, they stay at a constant level and low notes seem to induce them- don’t know if that’s relevant!



    thanks in advance :)
     
  2. 6stringcowboy

    6stringcowboy Friend of Leo's

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    Welcome.

    Take it to a good tech.
     
  3. loudernhel

    loudernhel TDPRI Member

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    I believe London is still pretty much locked down so taking it to a tech might be an issue.

    If I'm reading you correctly, the volume of the unwanted noises doesn't change with the volume of the amp. That suggests that if you do have a tube problem, it is the power tubes. Generally they go first in an amp anyway, and the EL84s in the Classic 30 often don't last all that long.

    Can Amazon UK send you a new set of matched EL84 power tubes?

    I used to work on Classic 30s a bunch and have one with "issues" right here next to my desk. Unless the newer ones have changed, they are fixed, non-adjustable bias. If you pop new tubes in, it should bias fine but may not be optimal. So once y'all are out of lockdown it might be worth popping over to your friendly neighborhood amp tech to check the bias.
     
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  4. Milspec

    Milspec Poster Extraordinaire

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    Sounds like a bad 12AX7 tube (or two). If you have a good spare, swap them out one at a time until you find the culprit. Likely the last tube prior to the power tubes.
     
  5. Henry Mars

    Henry Mars Tele-Afflicted

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    I don't know how long it has been since you retubed it ... it sounds like a tube problem .. if the volume control doesn't effect the nois level it is probably the pwr tubes. I would just go ahead and replace all of the tubes. They don't last like they used too. This amp doesn't need biasing so no particular skilll is required to do it.
     
  6. uriah1

    uriah1 Telefied Gold Supporter

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    Go one by one. If it happens to be a power tube you can replace and have a tech bias it later .. imho
     
  7. Dacious

    Dacious Poster Extraordinaire

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    It's probably a microphonic preamp tube - they're the little tubes. Try swapping them. Turn the amp off and you can change them with no problem, they are self-biasing. Having a spare one is a good idea - £10 or so.

    If that doesn't cure the problem, it is likely in the power tubes. An element may have broken and be sympathetically vibrating with certain frequencies. They get very hit, this does happen especially with pentodes like EL84s and EL34s.

    If your amp is 90s it should probably be serviced. The electrolytic caps will be gone. You could buy a new set of matched tubes and put it in, but for best sound and reliability the amp's bias should be checked and reset.
     
  8. FenderGuy53

    FenderGuy53 Poster Extraordinaire

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    Turn the amp on. Using a pencil, tap the eraser end to each tube, several times. If you get a "sprung rubber band" or bell-like, gong sound, then replace the tube.
     
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  9. teleman1

    teleman1 Friend of Leo's

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    It works fine for about 5 minutes then begins to screech and scream.<<<<<Find a pencil with an eraser. Be ready to roll right when it warms up. Tap the tubes. Especially v1 & v2 & the power tubes. See, if you can induce the sound, before the sound/screeching starts. If it is one particular tube, this can isolate it. THe classic 30 COOKS, it is a hot amp when it runs. My classic 20 ran the same way. Hope it isn't you power tubes cause you will be buying a quad at once.
     
  10. teleman1

    teleman1 Friend of Leo's

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    UH! this guy here needs a suspension. Obviously copying my ideas. But he doesn't say as much and types faster:lol:
     
  11. teleman1

    teleman1 Friend of Leo's

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    What Fenderguy53 and i are suggesting is probably the first thing you should do. A fairly safe procedure. OH. Do turn the volume up past one so you hear. Look at the tubes for any flashing.
     
  12. misterdontmove

    misterdontmove Tele-Meister

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    Tube replacement is the only real user maintenance recommended on a tube amp. You may as well try it since you can do it yourself, and it might do the trick. You can always bring it to a tech if it doesn't work or even if it does and it's time for routine maintenance.
     
    FenderGuy53 likes this.
  13. schmee

    schmee Doctor of Teleocity

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    Could be microphonic power tube or pre tube. Try tapping on various tubes and see if one is more noise prone.
     
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