May Overdrive - 2 curious problems

[rockaffe]

Good morning (yep, in Italy is 7am now ), I have two curious problems with the May Overdrive of which I spoke here:

https://www.diystompboxes.com/smfforum/index.php?topic=121615.0

Here are the problems:

- The pedal works and sound fine but, when I turn the guitar volume to 0, a really loud whistle starts.

- I added a volume control (100K Log) connecting the circuit output to lug 3 and using lug 2 as my new output, but the control does't work. I can hear "something" turning down but definitely not the pedal volume

Any ideas on how to solve these two problems?

BTW this is the project page: https://paulinthelab.blogspot.com/2017/09/may-queen-overdrive-originally-by.html

Thank you!

[nickbungus]

Have you got pin 1 going to ground on the volume pot?   If not,  try that

[rockaffe]

Thanks, this solved the volume problem, now it works correctly.
Still got the whistle problem. I've tried two different guitars, and the problem is there with both...

[PRR]

Isn't the 10K trim-pot the volume control? It does essentially the same thing as a potentiometer across the output.

I don't see why it should whistle. Since it happens at ZERO guitar impedance, I would try about 5K in series with the input cap.

[pinkjimiphoton]

bad guitar cord to the input of the effect
bad ground somewhere
cold solder