Hi Jason, Suddenly, I thought what you said could possibly be right. But then, we are not talking high frequencies for that capacitive coupling, unless there is a breakdown of the insulation. If that would be the case, a mains line tester (with a neon lamp) has always shown that kind of a situation. But that does not seem to be the scenario. Now that said, wanted to have a look at spikes, if any, with a scope. Wonder, wonder .. There seems to be some potential difference between the capacitor GND and the GND of the scope. Nothing else connected in between. So there, you could be right, there could be a parasitic capacitive coupling between primary and secondary. But that said, the neon tester test didn't really show up either. A bit weird though. Cheers, Manu On Mon, Oct 22, 2018 at 7:18 PM Jason White wrote: > > I would strongly suspect that the transformer (if connected to mains) is > the source of the 80Vdc. > > No mains connection is entirely free of transients and noise. > > There also may be some nonideal characteristics in the transformer such a= s > capacitive coupling between the primary and the secondary. > > > -- > Jason White > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .