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YBA-1 Guitar amp makes a chirp sound

Discussion in 'Repairing Electronics' started by yba1user, Aug 1, 2011.

  1. yba1user

    yba1user New Member

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    I have an issue with my recently refurbished Traynor Yba-1 (1972)
    It sounds OK until I hit a note on the high E string above the 12th fret. ( guitar)
    At that point the note sounds more like a chirp than a musical tone.
    It doesn't happen with all of the notes up on that register....just a few.
    Is there a cap value or something I should look for on the tone stack?
    I can post a pic of the chassis if needed.
    I did lower the cap value on the volume control but that did not help. any Ideas
     
  2. gots2no

    gots2no New Member

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    That is strange. The amp is the problem? Does the tone/ high control make a difference?
     
  3. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    I would suggest you use a scope and a signal generator to see what's happening, I wouldn't be surprised if it's distorted at all frequencies, just that one is particularly bad.
     
  4. dave

    Dave New Member

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  5. unclejed613

    unclejed613 Well-Known Member

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    i used to own a YBA-1 many years ago. a couple of questions:
    1) do you play with the amp on top of the cabinet?
    2) how old are the tubes?

    the reason i ask this is that i used to have the amp on the cabinet until i found out it shakes the tube elements loose, causing microphonic tubes, and actually in some cases breaking spot welds in the tube elements. this is EXPECIALLY true with bass amps. in many cases the microphonic tube will react at a particular frequency if the damaged tube element is of the right size to resonate at that frequency. with no input, and all gain controls up full, lightly tap on the tubes one by one with a screwdriver handle. any popping or crackling is a sign of a bad tube. any transmission of the sound of the tapping is a microphonic tube. when tapping on the tubes, be ready with the standby switch. i recently repaired an amp with a similar problem. when i got to the output tube that was bad, the problem was a broken spot weld on the grid. when i tapped the tube, there was a loud pop from the speaker, and the tube began glowing cherry red. always make sure the amp has a load. tube amps MUST NOT be run unloaded.

    a couple of things help make your tubes last longer. play the amp on the floor or placed on something dense enough to minimize vibration. use ruggedized tubes if you can get them. mil surplus tubes will usually last a lot longer in environments where there is a lot of vibration. there are also some russian made tubes that are ruggedized for guitar and bass amp use and abuse. a good cleaning of all the controls and touch-up of solder connections in the amp is probably in order. you might also want to have the amp recapped as well. old electrolytics that are surely by now drying out will cause oscillation problems
     
    Last edited: Aug 2, 2011

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