Tonebender Mk III - adding a pulldown resistor

[tracer03]

So, I've built a couple of Tonebender Mark III's using the layout here (link) - and none of them have ever had a switch popping problem - that I've noticed, anyway.

Until today...Finished boxing one, and hooked it up to test, and it's got a pretty loud pop when the switch is pressed. Could I just 'add' a 1M pulldown resistor from Input to ground on the existing layout - connecting to the bottom lead of the 100n Cap to ground (column 3, from left)? Or is there a better way to add it to the existing circuit?

Also, going forward, could I just make the layout 1 column wider and add a 1M to ground at the input before the 100n cap?

Thanks in advance!

[nocentelli]

Yes, you can just add a resistor where you have suggested and yes, you can just make the layout one column wider next time to accommodate it in future. Be aware, however, that not every example of switch popping is caused by lack of a pull down resistor, and so adding one might not cure it.

[tracer03]

I was going to use some alligator clips to add the resistor to test it first - what would some other causes be?

[nocentelli]

There are a few possible reasons, it can be caused by the sudden current demand/flow to ground through the indicator LED (which can be lessened by a higher value current limiting resistor, a more efficient "superb bright" LED, a cap in parallel with the CLR - or all three). Sometimes the footswitch contacts can "bounce": Not much can be done about this apart from replacing the switch, buffered bypass using a soft momentary switch is often preferred by large scale manufacturers.