# Unison Double Tracker



## AK7IN (Apr 5, 2019)

Pedal makes a popping sound when turned on and off. Any suggestions would be appreciated.


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## zgrav (Apr 5, 2019)

some useful info from a good resource:  http://www.muzique.com/news/pulldown-resistors/


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## AK7IN (Apr 5, 2019)

Thanks for responding but it does have a 1meg pulldown resistor.


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## zgrav (Apr 5, 2019)

I realize most projects here already have pull-down resistors, but the article may give you insight into whatever might be causing the popping in your build.  Plus, even if you have a pull-down resistor, you could have a bad solder connection on it.  Folks reading your question have no clue as to what you have already considered, tested, tried, and ruled out as a possible cause.  If you want more specific guidance you will likely need to provide those kinds of details about your build and the testing you have already done to get suggestions of other things you could check.


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## AK7IN (Apr 6, 2019)

I checked the 1meg resistor and soldered it back. It is fine. Could it be a bad electrolytic cap? 
Would raising the 1 meg to 2 or 3 meg help? If I press the footswitch on and off several times the popping stops for a while but eventually comes back. Other than the popping the pedal sounds great.


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## zgrav (Apr 6, 2019)

check to make sure you don't have any power from the LED wire shorting to your audio connection at your  footswitch.  maybe you are getting some voltage at the switch that is isolated from your pulldown resistor when the effect is switched out from your signal.


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## music6000 (Apr 7, 2019)

1. Try pulling Firmly on the wires you have Soldered One by One to the Footswitch.
I have experienced this a few times with pedals that had a Dry Joint & the Clicking of the Footswitch enhances the Pop.
2, Reflow the solder on your Footswitch connections including Links.


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## AK7IN (Apr 8, 2019)

Reflowing the  solder on the footswitch did not correct the problem. Could the footswitch or the input capacitor be defective?


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## zgrav (Apr 8, 2019)

try taking the two TL072 ics off the board if they are socketed, and see if you get any popping in the PCB when you power it up and use the footswitch.    you won't get an audio signal through the effect when the ICs are out of the circuit, but you might or might not get the popping.  and then if there is no popping in the circuit with both ICs out, try putting one of them back in and check,  and then do the same with the other one.  that might help narrow down the source of the popping.


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## AK7IN (Apr 9, 2019)

Took both TL072 ics off the board, the popping is still there.Took the other ic out and the popping is still there. Finally took the transistor out and the popping is still there.


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## zgrav (Apr 9, 2019)

Try temporarily disconnecting the LED wire that goes to your footswitch and see if that makes the popping stop.


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## music6000 (Apr 9, 2019)

It's Picture Time
Need Photo's Front & Back of PCB & Detailed picture of Footswitch, In & Out Jacks.


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## music6000 (Apr 9, 2019)

AK7IN said:


> Reflowing the  solder on the footswitch did not correct the problem. Could the footswitch or the input capacitor be defective?


Did PedalPCB supply & install Spin FV-1 IC .


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## AK7IN (Apr 12, 2019)

Putting a 100k resistor to the output jack lugs has solved the problem. Can someone explain why it solved the problem?  Yes PedalPCB supplied and installed the Spin FV-1 IC


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## Robert (Apr 12, 2019)

The PCB didn't have a pulldown resistor on the output.    Typically this isn't an issue if the circuit after it has a pulldown on the input, but occasionally the absence can cause popping. (Especially if C6 is leaky)

For the sake of true bypass, you _might_ want to move the resistor so it connects between Ground and the Output pad of the PCB.


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## AK7IN (Apr 12, 2019)

Excuse my ignorance but would it work by connecting the 100k from lug 5 to lug 7 of the footswitch?


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## Robert (Apr 12, 2019)

AK7IN said:


> Excuse my ignorance but would it work by connecting the 100k from lug 5 to lug 7 of the footswitch?



Just to be sure we're counting the lugs the same way.... 5 being the center lug, 7 being the top right lug.... Yes, that would work.


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## AK7IN (Apr 12, 2019)

Yes that is how i am seeing it. Thanks to everyone for their help.


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## Sasan (Dec 11, 2019)

Does anyone here have sound samples of the Unison DT?


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