GGG Thunderchief oscillation problem's ....is there a common fix?

[rosssurf]

I have purchased and built the Thuderchief from GGG link seen here http://www.generalguitargadgets.com/pdf/ggg_thunderchief.pdf
I have built it stock with all J201's with the exception of using .003 caps in both positions right before the volume pot(instead of called for .0022's).
I am having quite a bit of osillation at high gain settings. The pedal sounds great otherwise. I have tried moving around various wires and keeping them reasonably short.  I have done a search and read a few things but not much specific to this build.


Are there certain things on the Thunderchief that tend to cause this oscillation?

How might my use two .003 caps in place of the called for .0022 affect the sound?

[rosssurf]

Surely I'm not the only one that has had this problem..right? ...maybe ....no!??   good googly moogly

[ildar]

The first thing to check is jfet bias. Measure your voltage at the drain of each jfet. Should be about half the supply voltage, or 4.5v or so.

[rosssurf]

Thanks Ildar I have and all measure 4.55v since my supply is 9.1v