Trying to fix a DOD FX90 Delay pedal. It works, but emits a screech (feedback) when the Mix control is turned almost all the way clockwise. Turning any of the 3 internal trim pots to any setting, has no effect on the feedback. My circuit board is a Rev H, but the only schematic I can find online is Rev A and is different enough to make debug difficult. I changed a few caps working from the output of the MN3005 chip and near what I assume is the Feedback trim pot, but no improvement.
Does anyone have a Rev H schematic?