Crackling and Losing Volume

Discussion in 'Amp Central Station' started by Recce, May 6, 2019.

  1. Recce

    Recce Tele-Afflicted

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    I have a 68 Vibrolux Reverb Reissue. Last night I was playing it and it started making a crackling sound then the volume dropped. The volume came back up but then it repeated. Would this be caused by power tubes going bad? I actually have a matched set I could put in it. The Reverb Tube recently went out. Although it’s relatively new considering changing all the tubes but think that is probably overkill.
     
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  2. peteb

    peteb Friend of Leo's

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    If it is a tube, that is unusual tube behavior.


    Crackling and volume loss are both consistent with a bad / intermittent connection in the signal path.
     
  3. Recce

    Recce Tele-Afflicted

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    I will check that. I have a pedal board in my garage with all my pedals hooked up. I will disconnect it and see if the problem goes away.
     
  4. ce24

    ce24 Poster Extraordinaire

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    Clean tube pins and sockets...start cheap and quick then keep moving up the list till you find it.
     
  5. 24 track

    24 track Doctor of Teleocity Silver Supporter

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    also clean and exercise the pots, some times the traces get corroded in one spot and it can affect this type of issue
     
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  6. ale.istotle

    ale.istotle TDPRI Member

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    Find the source first.
    Take all effects out of play, try a different cable.
    Make sure the guitar works on a different amp.
    If it's the guitar, check jack and connections, clean the pots, switches.
    If it's the amp make sure you know how to do safely - then clean the pots, jacks and connectors, switches and sockets.
     
  7. Ripradiant

    Ripradiant Tele-Afflicted

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    If the crackling and vol loss occurs when you're moving the volume or other knobs
    ... I would start with a pot cleaning using deoxit or similar cleaner.
     
  8. King Fan

    King Fan Friend of Leo's Ad Free Member

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    Tube swaps aren't a bad idea, since you can do 'em all in a few minutes. I'd try the rectifier and power tubes first.
     
  9. Milspec

    Milspec Friend of Leo's

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    A power tube getting loose can do that. It doesn't really come back to normal unless moved though. I would start with making certain that all tubes are fully seated, my Blues Jr. had that same problem and was correctd by re-tensioning the sockets.
     
  10. LGOberean

    LGOberean Doctor of Teleocity

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    I read this post with interest, given a recent experience of my own. But in my case, it was my Vox Pathfinder 15R, so no tubes to fuss with/blame. I discussed the occurrence over in the Pathfinder club thread, but I described Recce's "crackling sound" as sounding "fizzy." (Since "fizzy" is sometimes used in our discussions to describe how an amp's Gain might sound, "crackling" may be the better descriptor here.) But the same thing happened in my case: crackling/fizzy sound, the volume drop, followed by the volume kicking back in, the a while later dropping again.

    A couple of TDPRIers suggested that it might be the optocouler. I took that under advisement, but decided to start with the simple and cross the optocoupler bridge if it came to it. So I used some contact cleaner and worked it in a bunch of times with the 1/4" male plug of my instrument cable. I have plugged into that same offending PF15R consistently since then, and the problem seems to be gone. As I observed in my comments in the aforementioned club thread, I have long hair, my wife has long hair and we have a dog and two cats, so one of us is always shedding. :oops::twisted: Since it seems to be working just fine now, I'm guessing my amp had a "hair ball" it needed to work out! :twisted:

    So at least in my case, peteb's observation about the symptoms being "consistent with a bad/intermitment connection in the signal path" seemed to be the problem. Hope yours is as easily fixed.
     
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  11. Paul G.

    Paul G. Friend of Leo's

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    You may be losing bias voltage. Check around the bias pot, resistor and cap. Check the solder joints.
     
  12. peteb

    peteb Friend of Leo's

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    And I would add that bad tube pin connections and non maintained, bad pots, are are bad / intermittent connections in the signal path
     
  13. Bartholomew3

    Bartholomew3 Friend of Leo's

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    I had this problem with a twin after putting in some old power tubes last week - switched back to new JJ 6L6 and problem gone. Have pretty new caps and pre-amp tubes.

    Smacked the top of the amp a couple of times also. I may have a magic touch or got lucky.

    Made sure all the tubes were tight, moved a few things slightly.
     
  14. Recce

    Recce Tele-Afflicted

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    I have not gotten back to this amp yet. I did check both guitars I played through it last night and they worked fine through either my Princeton or my AC15C1. One guitar is my Les Paul and it sounds better through the VOX. I will make sure the tubes are tight and bypass my pedal board in my garage and see if that helps. Anything much past changing tubes is past my skill level and I will need to take it to a tech. It is in my garage which is heated and cooled but maybe some bugs or a spider got into it and I will check for things that could have gotten into the amp. I will let you know if any of that helps.
     
  15. Recce

    Recce Tele-Afflicted

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    So I went to my garage to play with the amp. I unplugged it and laid it on its face. (First rule of tube amps unplug it) Looked inside and it looked clean but I then took my shop vacuum and vacuumed any dust out of it top to bottom. Then I took one hand and gave each tube a little push in. (Second rule: one hand only). Stood it up and plugged it back in. Some pops and crackles but then it calmed down.

    Then I made sure all the cables through my pedal board were plugged in well and played it for an hour. No problems.

    Prognosis: lose cable connection.

    I am somewhat new to pedal boards and something loose caused a problem I didn’t recognize.

    Thanks for everyone’s help.
     
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