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Many thanks Billy this was very helpful. Knowing the power scheme has made troubleshooting much faster. Can you please confirm that the BIAS will only sweep the frequencies when Sens is at zero, and not when engaged?

Ive been trying to google how to tell the input impedence of my meter but not finding anything specific. At max ohms (2m) touching the probes together gives a reading of zero.

Initial probing shows that VA isnt connected to the pad on pin 1 of Q1 at all. Ive made jumpered connections and Drain is now at supply voltage (about 7v), but Im getting some inconsistent results on different points of the schematic. And the sens knob still doesnt appear to work. Also the Decay knob doesnt appear to change anything either but I dont know if thats another symptom of the same issue.

Even with jumpered VA connections Im only getting 1.1V on Gate of Q1, and still getting low readings for Q2 and Q3.

I have a feeling that the pads may be a little less robust than usual on this particular one board, or I was unprecedently rough with my component stuffing. Ive built over 50 pcbs at this point and have seen a couple of boards where the pads werent properly adhered to the traces or planes. Ive certainly lifted some pads and traces when doing aggressive troubleshooting, but not in the initial construction like on this board. Im ordering another and trying again and putting it down to experience.

On the new board Ill build out the power rails first and make a post with readings to make sure im on the right track.

Thanks again for your time Billy.