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old tube amp static when playing a C

Discussion in 'Amps and Cabs [BG]' started by MattZilla, Jan 6, 2017.


  1. MattZilla

    MattZilla

    Jun 26, 2013
    CNY
    ~'76 B15N, recapped n tubed in '15, new beta 15a in '13, home and jamspace use only since '12. I almost never play it without other musicians making noise, but just got my first P bass and have been soaking in the chocolate :) and I really don't know how long it's been doing this for.

    It does this on both 8th fret E string and 10th fret D string C's.

    I wiggled all of the tubes in their sockets a bit (just a few swirls per tube). Could this be solved by some deoxit on the pins and over ten seconds of wiggling per tube, or is this a sign of something on its way out?
     
    Last edited: Jan 6, 2017
  2. Grumry

    Grumry

    Jul 6, 2016
    Nashville
    Does changing the eq do anything to it when you play these notes?
     
  3. markjazzbassist

    markjazzbassist Supporting Member

    Apr 19, 2005
    Cleveland, OH
    subbed
     
  4. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    There are several possibilities, including:
    - Static is a sign of a bad tube.
    - Static can also occur when a tube socket contact is loose. When you pull or insert a tube, you can tell if it is too loose in the socket. The fix is to re-tension the socket terminals. This is done by carefully pinching the terminals closed, then reinstalling the tube. Google "retensioning tube socket" will show you how to do it.
    - It never hurts to clean the socket terminals and tube pins. This is done by scrubbing with Deoxit.
    - It could be a bad solder joint, resistor, or capacitor.
     
  5. it could in fact be one or more of many things. You need to take your amp to a good tube amp tech to get it serviced and put to rights. Re-tensioning and cleaning tube sockets exposes you to possible shock hazards even with the amp off and disconnected from the mains. The money you save by trying to fix the amp yourself is far less than your life is worth!
     
    Last edited: Jan 8, 2017
    webmonster likes this.
  6. markjazzbassist

    markjazzbassist Supporting Member

    Apr 19, 2005
    Cleveland, OH
    I've got a power tube that rattles when I hit a low note, when I tap it I hear a noise through the speaker, the other power tube doesn't rattle or make a noise when I tap it, neither does the tube rectifier.

    safe to say I think that tube is on it's way out.
     
  7. Whatever it is, it's got a mechanical component.
    By that I mean it's not likely a case of something being out of spec.
    Something is physically moving at that frequency.
    Could be a tube socket issue.
    I agree it never hurts to clean and retension the sockets.
    It could be a bad solder joint that has rattled back and forth
    for years before getting intermittent.
    It could be a carbon comp resistor.
    They can actually crack.

    If and only if you know what you are doing,
    try wiggling wires and connections inside the amp
    with a wooden chop stick while the amp is on.
    That has been known to find a lot of bad connections.

    While you are at it, you can use that same chop stick to lightly tap on each tube.
    If you start hearing noises when you do, the tube that you are tapping could have issues.
     
    markjazzbassist likes this.

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