static like noise in a Deluxe

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by doctord02, Jun 18, 2005.


  1. doctord02

    doctord02 Member

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    Hi all-

    I have a '65 Deluxe that was purchased from a fellow forumite that was nicely set up and modded by Dave Allen. It has the first channel reworked at a Brown Fender tonestack circuit with the single tone knob. The trem channel is pure Blackface. It's a really sweet amp and covers both my Brown and Blackface needs... But... It has a vibration/frequency dependant static like noise in the decay of single notes like fretted A's and D's on the lower strings - but only on the Brown/first channel. I have ruled out bad tubes, and have confirmed that it's only happening when I used the internal speaker. If I disconnect it and run and extension cab all sounds fine. Also, I have run the internal speaker with an external amp and the speaker itself is fine (a Red Fang, in case it matters). I've swapped out the tubes and I still get the static, so that leads me to believe it's a cap or resistor on that first channel.

    The sound is a sort of static like crackle, not loud, that follows these particular notes. If any of you more technically savvy guys have run into something similar, I'd love to get a head start on my troubleshooting process.

    Of course, I'll also be emailing Dave Allen, who is both a Fender scholar and a gentleman, but I'd like to take a crack at it myself first.

    Thanks in advance-

    Dave
     
  2. doctord02

    doctord02 Member

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  3. doctord02

    doctord02 Member

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  4. Swarty

    Swarty Member

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    Could be a leaky coupling cap, which can sound like a blown speaker. Could also be a loose connection/bad solder joint. Does it make the noise when you smack the amp ?
     
  5. Euthymia

    Euthymia Member

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    Sounds like a good candidate for a "chopstick test."

    This does expose the technician to voltages that can kill, so if you don't know about the safety precautions, don't try it.

    Remove the chassis from the cabinet to expose the circuit board, then attach a speaker, and a signal source (signal generator, CD player, whatever).

    Power it up, and take a non-conductive probe, such as a wooden or plastic chopstick (or a Sharpie pen), and poke it at the component ends. When the sound craps out, you've found the bad joint or component.

    Chopstick testing is definitely a time to have the hand that's not holding the chopstick stuck in your back pocket.

    The other night I was out at a Vietnamese restaurant with my girlfriend, and when I picked up my chopsticks, I had the impulse to stick my left hand in my back pocket. Sad, in a way.
     
  6. doctord02

    doctord02 Member

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    I havent tried that, but it doesnt make the sound if I'm cranked on the other channel - even if the first channel is still turned up. I'm kinda banking on the bad solder joint theory and will chopstick it when I have the time. The sound does not remind me of a bad speaker, it's definitely an electronic static sound that is tied to the note being played.
     

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