Bad solder joint noise? Or to much bass

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by alanfc, May 19, 2005.

  1. alanfc

    alanfc Member

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    Feb 4, 2004
    hi,
    I had my amp retubed and biased a few weeks ago, and the tech was wiggling & testing stuff (with me in the room) and he was getting this scratchy static-y sound from the amp. He said it was an old solder joint gone bad, then he fixed it on the spot.
    Its a 12 year old Rivera R-55-112.

    Cut to, now, with my new Eminence Governor speaker in there. At 4+ on the master volume, and the bass at about 4.5, the static/scratch sound comes back again - what is that ????

    I notice that the back magnet thingy of the new speaker is about 1 inch from the power tubes. I can't remember how far the old original Rivera/Celestion GT-85 was. But I think it was farther away.
    so, is it the new speaker, having a heavier low end, even though I don't pour on the Bass ?
    Is this happening even with my tech's re-solder job? Or did I disturb it somehow?
    His solder job was when I had the GT-85 in there. He played it ==loud= like with the master on 8 and preamp on 6. And we were satisfied.
    Any diagnosis I can make with these clues??
    thanks
     
  2. Ayan

    Ayan Member

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    Feb 2, 2002
    Location:
    Los Angeles, CA
    You can try this: play the amp through a separate cabinet, if you can. If the noise is still there, it cannot be a "mechanically induced" problem, meaning it's not the amp vibrating so hard that it causes some rattling, shaking a connection or component. If this is the case, take the amp to a repair shop unless you know how to troubleshoot and amp -- and ideally, you'd use a scope as well.

    If using a separate cabinet gets rid of the noise, then I would suspect a couple of things:

    1. The speaker -- although the problem a bad speaker causes doesn't sound like what you've described.

    2. A tube? You could try to -- using overn mittens!! -- have someone play the guitar for you while you grab and firmly secure one tube at a time. If there's a bad tube in there, this method may help single it out, as it the noise will probably go away or get worse when you grab the bad tube.

    3. I don't know the amp in question, but sometimes, amps with FX loops use the switch on the jack to close the circuit when nothing is plugged into the loop. You could try using a patch cord across the FX loop and see if that makes the amp sound right. If so, then cleaning or replacing the switching jack in the loop (which should be the return jack) will fix the problem.

    If the above fails, I'm afraid that barring opening the amp up and putting a scope to it, I am not sure what else to suggest.

    Gil
     
  3. alanfc

    alanfc Member

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    OK thanks alot this is good.

    still I'm curious in general, Regarding the big magnet thingy at the back of the speaker-
    Its less than an inch from one of the power tubes. Does anyone think that's too close, like it could have an effect? I believe by its natre the Governor is bassier than the GT-85 yes? Could the combination of these 2 factors be affecting things?
    THanks again Ayan
     
  4. Moat

    Moat Member

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    I own a Boogie MkIIIc 112 combo (w/push-pull control knobs) that acted like you describe - found a few dirty/scratchy pots/knobs that were vibrating at high volumes/bass settings. Cleaning the pots (w/spray tuner cleaner) cured the problem.

    FWIW!
     
  5. alanfc

    alanfc Member

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    Feb 4, 2004
    OK thanks-
    this is one of the jobs the tech did , so I'm left with one clue- when I turn down the bass , the problem stops.
     

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