> On Aug 17, 2016, at 2:07 PM, tony duell <ard at p850ug1.demon.co.uk> wrote: > > >> When I used a variable load on the 12V both the amplitude and the period >> varied. More load less amplitude. > > More load _reduces_ the ripple? That's very unusual. Perhaps a parasitic oscillation that's defeated by more load because now the loop gain is below 1? paul