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  1. #1
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    Default Guitar amp dies then comes back to life after turning power on

    I have a carlsbro amp that for the last few years will play for a few minutes and then die on me. I turn the power off and then turn power on a few seconds later and it will work. This cycle continues for a while and then not even turning the power button works anymore. The amp has hardly been used. Anyone know what is wrong with it. image.jpg

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  3. #2
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    I'm no amp expert, far from it. But try playing 'Smoke On The Water', that should fix it
    -Scott

  4. #3
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    sounds like a heat issue to me.
    could be a dodgy cap.
    The music shop at Knox has a good repair guy.

  5. #4
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    Thanks fly, might try that but i put some contact cleaner into some of the input jacks and the amp didn't cut out after an hour so not sure what to make of it.

  6. #5
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    does sound like heat contraction expansion issue
    when it cuts out does the power indicator light go out as well?

    some PCB based amps can be a real can of worms and some techs wont touch em

    try researching the issue with the model of your amp - could be common
    ray c
    dunno what's more fun, buyin' the tools or usin' em'

  7. #6
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    If contact cleaner seems to have done the job, then it'd be worth your while to pull that PCB and thoroughly checking for dry or broken solder joints where the jack pins meet the PCB pads... poorly soldered joints there can literally break simply from the jack flexing when leads are plugged/removed.

    While you have the PCB out it's also worthwhile to check any nearby joints on the PCB, 'cos the c/cleaner might've had a bit of "overspray" thru the jack into nearby parts of the PCB and thus temporarily fixed the problem joint.

    If you do find any problematic joints, it's usually a straight forward matter to resolder 'em; I recommend using a wick to remove the old solder and NOT just throwing on a bit of flux and applying heat to the old solder, unless you like pulling PCBs in and out on a regular basis.
    I may be weird, but I'm saving up to become eccentric.

    - Andy Mc

  8. #7
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    The contact cleaner may have temporarily cooled the hot spot
    Whatever note you blow youre never more than a semitone away from the correct one....(Miles Davis)

  9. #8
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    Quote Originally Posted by old_picker View Post
    does sound like heat contraction expansion issue
    when it cuts out does the power indicator light go out as well?

    some PCB based amps can be a real can of worms and some techs wont touch em

    try researching the issue with the model of your amp - could be common
    Thanks guys for your responses. Power light doesn't go out, you'll be playing and then the sound just dies out. Haven't found much on this particular amp in the research I have done. It's a solid state amp, how hard are the PCBs to take out?

  10. #9
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    Sounds like cleaning contacts may be the way to go

    Carlsbro Cobra 90 - diyAudio

    I had a similar problem with a bass amp once - it was the effects loop too.
    The other day I described to my daughter how to find something in the garage by saying "It's right near my big saw". A few minutes later she came back to ask: "Do you mean the black one, the green one, or the blue one?".

  11. #10
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    Thanks Peter.

  12. #11
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    Those little solid state amps often have a Power Amp IC that can generate enough heat to 'de-solder' itself.
    The solder joints become 'dry' or cracked & sometimes they connect & sometimes they don't.
    Easy fix if you have a soldering iron & know where to look.
    Cliff.
    If you find a post of mine that is missing a pic that you'd like to see, let me know & I'll see if I can find a copy.

  13. #12
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    Quote Originally Posted by Cliff Rogers View Post
    Those little solid state amps often have a Power Amp IC that can generate enough heat to 'de-solder' itself.
    The solder joints become 'dry' or cracked & sometimes they connect & sometimes they don't.
    Easy fix if you have a soldering iron & know where to look.
    Thanks Cliff, half way there, ie have soldering iron not entirely sure where to look though.

  14. #13
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    Look for any IC's with (hopefully) big heat sinks...
    I may be weird, but I'm saving up to become eccentric.

    - Andy Mc

  15. #14
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    Thanks Skew, that brings me a step closer.

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