Crackle and pop!

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by muff77, Oct 9, 2008.

  1. muff77

    muff77 Member

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    Hi

    I have an old Sound City 50Plus that's started to make all these loud crackling and pop noises. It starts when I switch on both the mains and standby and lasts for about 30-60 minutes. Then the amp is dead silent like it should be. The power tubes are about 10 months old but I have no idea how old the pre amp tubes are. I would guess about 3 years. The sockets are probably a lot older...

    Any idea what the noise is all about?

    Thanks!
     
  2. SatelliteAmps

    SatelliteAmps Member

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    Crackling noises can be all kinds of things. Considering it is happening after it warms up, I am leaning towards either a cold solder joint, or a resistor going bad somewhere. It could be a lot of other things as well though. This might best be handled by a tech who can test the amp, and who would be comfortable poking around inside.
     
  3. stuagu

    stuagu Member

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    please dont try & fix it yourself... give it to an amp specialist, its your life your dealing with.
     
  4. muff77

    muff77 Member

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    OK. Thanks!

    Could it be that the sockets are burned and needs to be changed?

    To describe the noise a bit more, - it's like when you blow heavily into a microphone. Sort of a constant distorted radio crackle.
     
  5. stuagu

    stuagu Member

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    to be honest, it could be anything.
     
  6. muff77

    muff77 Member

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    This happens BEFORE the amp warms up. I switch on the power, let it sit for a couple of minutes then switch off the bypass. The noise appears instantly and for normally 30mins, which leads me to think that there's something happening when the amp or tubes are warmed up properly.
     
  7. stratman_el84

    stratman_el84 Member

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    Well, about the only thing you can do without having to poke around in the guts where there's dangerous voltages is try swapping out preamp tubes with known good ones to see if that fixes the problem. Failing that, I'd take it to a tech if you're not experienced with working on amps..that thing carries enough of a wallop to stun a charging rhinoceros, and fry us puny humans!

    Cheers!

    Strat
     
  8. muff77

    muff77 Member

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    Ok. Thanks for your help guys!
     
  9. jay42

    jay42 Member

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    Simple test for one other source...kind of assuming it's a 4 input jack model? Plug a guitar cord into each input. You'll get buzzing, but if the crackling stops, it's one or more of the jacks...Cliff jacks just do that sometimes.
     
  10. SatelliteAmps

    SatelliteAmps Member

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    I am referring to the crackling stopping AFTER it warms up, not the crackling before. When a part warms up, it can sometimes change it's characteristics if it is going bad, or it is overheated. Finding it is not easy, nor for the inexperienced.
     
  11. acorkos

    acorkos Member

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    is the crackling audible with the volume controls turned down?

    do the tone controls have an effect on the noise?
     
  12. muff77

    muff77 Member

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    The crackling continues...
     
  13. muff77

    muff77 Member

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    After it's warmed up the amp is dead silent... That's why I suspect a burned socket or something...
     
  14. muff77

    muff77 Member

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    The crackling is there...
     
  15. SatelliteAmps

    SatelliteAmps Member

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    A burned socket wouldn't do this. This is the time to quit trying to diagnose it online, and let a professional take care of it.
     
  16. muff77

    muff77 Member

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  17. mark norwine

    mark norwine Member

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    see a tech.

    My guess? carbon comp plate load resistor(s)
     
  18. vds5000

    vds5000 Member

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    Hey there,

    Did you ever find out what the problem was? My buddy's amp is doing the same thing - crackling/wind blowing type sounds for the first 10-15min of the amp being on.
     
  19. VikingAmps

    VikingAmps Member

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    I'd try some new power tubes. I've had that happen to me on quite a few new production power tubes lately. Brand new out of the box.
     

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