Well you only acknowledged part of what I wrote. If pulling the PI didn't increase voltages, and it didn't really, then it's less likely that the OT leads need swapping. But I suppose it's easy enough to lift the feedback loop and see.
As far as what to expect from incorrect OT lead orientation I can agree, the near ultrasonic thing hasn't happened to me either. But I have seen it manifest in many ways ranging from motor boating to intermittent frequency dependent crackling, instant whistling or a steady screech. So it wouldn't surprise me if it could also cause an ultrasonic oscillation.
As far as what to expect from incorrect OT lead orientation I can agree, the near ultrasonic thing hasn't happened to me either. But I have seen it manifest in many ways ranging from motor boating to intermittent frequency dependent crackling, instant whistling or a steady screech. So it wouldn't surprise me if it could also cause an ultrasonic oscillation.
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