Fulltone OCD Version 3

[pnadora]

Hallo,
I recently builded a OCD Vers. 3 from this layout: http://tagboardeffects.blogspot.de/2012/02/fulltone-ocd-all-versions.html

At first I thought is was fine becasue it sounds like it should and the knob and the switches work as intended. But then I turned up the gain higher and there is a high-pitched feeping noise with the gain past 3 o clock. Like a feddback. I can filter it out with the tone knob, but thats not a very good solution. It is significantly louder in the HP mode (guess thats some kind of tone/presence effect and has nothing to do with the source of the feedback)

Is this problem known? Could it just be a bad IC or transistor in one of the gain stages?

I already checked the board for bridges etc. and its fine.

Thank you all very much for any help!!

EDIT: I just noticed I did not describe the problem in the title of the topic. Sorry for that!

[pnadora]

Update: Changed the IC and the transistors. Did not work :/

In the comments of the Layout there was someone else (user: SKarbu) having the problem. He changed the 220p capacitor between ic pins 1 and 2 to a higher value to filter out the squeal. Not sure if I want to do that since it would change the tone of the pedal and others did build the version 3 without problem. I am hoping for a different solution.