High pitched space-squeal from 535Q wah -- any suggestions?

Discussion in 'Effects, Pedals, Strings & Things' started by stratoskier, May 1, 2015.

  1. stratoskier

    stratoskier Member

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    Recently my Dunlop 535Q (the original 18v version) has started to periodically produce a loud, high-pitched squeal, sort of like a kid's space gun. The frequency of the squeal varies with the position of the pedal, so I can "control" it (?) with the wah. Very strange. Interestingly, once this starts, it does it even when the wah is clicked off, so that moving the pedal still makes the noise, though at a lower volume than when the wah is on. I can sometimes get it to stop by disconnecting everything and starting over, or by giving it a good solid kick.

    Has anyone else experienced this or have a clue as to a possible cause or fix? I'm using the original Dunlop 18V power supply, in case that matters.

    Thanks!
     
    Last edited: May 1, 2015
  2. Igotsoul4u

    Igotsoul4u Member

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    I would try another power supply if possible.
     
  3. stilwel

    stilwel Member

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    What pedal(s) do you have before or after it?
     
  4. stratoskier

    stratoskier Member

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    Tried another power supply with same results.

    No pedals before, just guitar straight in. After is a compressor (CS-2) into a Boss GT8. Interestingly, once it goes wacky, I can completely disconnect the input and still get the groovy spaceman thing with the pedal.

    As it is now, the wah is too unpredictable to use. When it does this, it's almost like a variable frequency ring modulator or something. That might be fun if it didn't hurt the ears so much.
     
  5. joegagan

    joegagan Supporting Member

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    The most problematic feature of the shortlived 18v version is the location of the trimpots underneath. I have had these in for repair where it looked like the owner had played too many rugby team parties outdoors, the pots were smashed in from playing on uneven surfaces. This may or may not be your problem.

    Are the mini pots in good shape? With the pedal plugged in and running, tap around lightly on variuos components to see if the chirp occurs. 2nd most likely cause would be a slightly intermittent solder on the board.
     
  6. joegagan

    joegagan Supporting Member

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    Note that dunlop moved the trimpots to a safer location for the revised version.
     
  7. stratoskier

    stratoskier Member

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    I hadn't thought about the trimpots being the culprit. When it went nuts this morning I did try turning them both and it didn't help. They look fine and it appears that the rubber feet give it enough lift to keep the pots from getting bumped.

    I'll leave the bottom plate off so that I can do some tapping next time it misbehaves. I also taped off the contacts on the two 9V battery connectors, just in case those were shorting on something. Nothing looks obviously suspicious in the guts, but cold solder joints are tough to detect (at least for me).
     
  8. stephanar

    stephanar Member

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    Every wah I've had did this, but only when playing high gain. If the wah is after gain effects, no problem at all. But it was more controllable. They wouldn't sustain the noise if I turn them off.
     
  9. stratoskier

    stratoskier Member

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    No, I know what you mean, but this is very different. It's before gain and when it starts this intermittent syndrome, there is no wah effect, just high pitched noise. As I mentioned, I can completely disconnect the guitar and it still produces the wailing noise. When it's working, the 535Q is great. When it does this thing, you don't want to be around it.
     
  10. tlpruitt

    tlpruitt Member

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    Does it squeal when the wah is powered by a battery?
    The first thing I would suspect is a cold solder joint, especially the solder joints at the DC jack on the PCB. It might be worth reflowing those solder connections. In fact, you may just want to go ahead and reflow all the solder connects...there are not that many.
     
  11. stratoskier

    stratoskier Member

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    Good idea. I'm going to pick up a couple of 9v and see if it still happens. If so, I'll heat up the iron and reflow the joints. With me, it's more like reblob, but I try.
     

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