Champ problems

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by CJW, May 16, 2005.

  1. CJW

    CJW Member

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    I have a sivlerface Fender Champ and there is a loud crackiling sound that comes from the speaker. I have replaced the tubes and have ruled out the speaker as being bad. At very low volumes (barely audible) the amp sounds OK, but hit the strings hard or turn it up and the crackling sound comes out making this amp unusable at this time. I would run this amp on 10 (volume) alot of times with no problems until now. Any ideas what I should look for?
     
  2. John Phillips

    John Phillips Member

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    A cracked resistor or solder joint. If it's a resistor, it may be very difficult to see any crack, you'll most likely have to poke around in there with something (insulated!) while the amp is on and see if you can duplicate the fault.

    It could also be a failing cap that's shorting internally, most likely the cathode bypass cap on the 6V6.

    Worst case is that it's a broken wire (or an arc) in the OT... hopefully not.


    FWIW, I once had a SF Vibrolux that did this, it turned out to be a wire that had never been soldered into the eyelet at the factory! Just left loose, quite clean and definitely not a joint that had not 'taken' or broken later. The funny thing is that the amp had run perfectly well for about ten years, until something must have disturbed it. I did get it cheap though, it scared the hell out of its owner ;).
     
  3. CJW

    CJW Member

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    Thank you. Now that I know what to look for, I just have to find the time to do it.
     
  4. Richard Guy

    Richard Guy Member

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    JP's advice/post is solid.

    If you still have issue

    You said that you replaced the tubes.....all of them? I just had a very similar issue and it was a faulty rectifier tube.

    You might re-tension the tube sockets. Please remove the AC cord from the wall and discharge the 20-20-20uf cap first. :eek:
     
  5. Fuchsaudio

    Fuchsaudio Member

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    Try replacing the cardboard under the tag board. Sometimes they get conductive and cause these kinds of problems. Nice thick hunk of cardboard can do the trick.
     
  6. twangoloco

    twangoloco Guest

    The bias is probably way too hot. In addition to switching out the electrolytics and filter cap cylinder I would seriously consider taming the bias down with a resistor switch. Fender had their Champs, VChamps, Broncos and Princeton Reverbs set with notoriously high bias coming from the factory making them distort early and blowing tubes prematurely. Once tamed the amps are much more user-friendly and the tone is ta die-for. My advice is take it to a tech quick or diy. TL
     
  7. TheAmpNerd

    TheAmpNerd Member

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    Is this THE Richard Guy?

    With the famed Boxed for Battle Ampeg V-4 head?
     
  8. Richard Guy

    Richard Guy Member

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    Are you referring to the box that sheltered 4 invisible Chucky Dolls with a V-4 inside as a red-herring? :cool:
     
  9. zachomega

    zachomega Member

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    Evil V4? What!?

    -Zach Omega
     
  10. TheAmpNerd

    TheAmpNerd Member

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    Ab so lutelye : )
     
  11. Richard Guy

    Richard Guy Member

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