Can't get rid of switch pop

[adam_bz]

Hi!

I've got a problemo with switch popping. I've built 100s of fx now but this particular one is giving me so jip!

The switch pops.
I've grounded the input, I've added the and resistor and cap. I've removed the led totally. I've replaced the 3pdt and power socket.

It doesn't do it in the test rig.
It doesn't do it if the input jack is not plugged in.

Running out of ideas.  The effect is working fine.

It's a swamp thing tremolo.

Any ideas?!

[midwayfair]

Post a schematic you're using.

Have you eliminated a leaky cap on the input or output as the possible cause?

Measure the input and output, switch the pedal, and see which one has a momentary spike of DC.

[adam_bz]

There's a spike on output. I have now changed all caps one by one, still popping!

I tried grounding the out put with a pulldown.

http://tagboardeffects.blogspot.co.uk/2012/01/monster-effects-swamp-thang.html?m=1

Using the schematic linked from the vero layout.

Any ideas?

[flanagan0718]

Not sure if it will help but I had a similar issue with a Deep Blue Delay clone I built a while ago. I was even using an optical bypass board and it still popped like the dickens. Then someone on the blog recommended putting a 100k resistor from the board out to ground and it worked like a champ...IDK something to try.

-Mike-

[adam_bz]

Believe it or not, it worked.

I dunno why tho! I'd already grounded the output before which made no difference, this time i ungrounded the input though.

Gotta love electricity.

Thanks again for your help

[Gui113m]

Does putting that resistor affect audio quality? (less highs, less volume, etc.)

[flanagan0718]

Nope, it made no difference in the DBD I did.

[brucer]

I've also run into this problem on a couple of builds (incl. when using a relay bypasss), but never did get it fixed.  Mike and Adam, what exactly did you end up doing that worked?  Was it running a 1M resistor from the effect PCB output to 1/4" jack/enclosure ground?  Any details would be greatly appreciated. 

[flanagan0718]

I've also run into this problem on a couple of builds (incl. when using a relay bypasss), but never did get it fixed.  Mike and Adam, what exactly did you end up doing that worked?  Was it running a 1M resistor from the effect PCB output to 1/4" jack/enclosure ground?  Any details would be greatly appreciated.

I wasn't using the relay bypass but my solution was soldering a 100k resistor from the PCB out to ground. That did it for me.

[brucer]

Thanks Mike.  I'll give it a try!

[adam_bz]

Me too. It didn't work with a pull down on the input as well. Only on its own.

Weird!!

[Gui113m]

Nope, it made no difference in the DBD I did.

That's great. I suppose it only alters output impedance then

[flanagan0718]

Yep


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[midwayfair]

Nope, it made no difference in the DBD I did.

That's great. I suppose it only alters output impedance then

It alters the LOAD. The output impedance precedes the load. You can view it as a voltage divider:

~source Z~
                |
            pulldown (load)
                |
                G

The pulldown is in parallel with the input impedance of any device that follows, whether it's your amp, a direct box, or another pedal. None of these things change the output impedance of your pedal, just as altering the output impedance of this device would not change the input impedance of your amp.

[flanagan0718]

Thank you Jon. That's a way better explanation than "yep". I knew that it worked as a pull down but didn't know how to explain it.


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