On 7/31/2012 12:27 PM, RussellMc wrote: > On 1 August 2012 03:58, Neil wrote: > Does it happen at all loads? I'd expect it more at light loads.=20 > Regulator may be stopping and starting with sudden voltage change=20 > piezo constricting ceramics. Changing grade may be all it takes - the=20 > cheaper wider tolerance parts are also more piezo sensitive. Assuming=20 > the reason is as I note, It shouldn't matter if it does not otherwise=20 > bother you. Some chance that RFI occurs at switching change. If clicks=20 > are accompanied by voltage steps into ceramics this may generate=20 > electrical noise or worse. . Russell=20 Only one load on this, and it is light -- the circuit it powers and the=20 regulator itself consumes ~1.6mA (at 12.1V input), and calculated that=20 it's delivering ~1.3mA (at 18.3V output). I dug up and old non-working unit and grabbed the tantalum caps from=20 that. Swapping *both* got rid of the clicking. Wondering if I can add=20 some output load instead. The word "piezo" added to my google search now gives me several links=20 explaining it (piezoelectric effect of capacitors)... quite=20 interesting. Since this is related to mechanical strain within the=20 capacitors, I'd like to eliminate it. I'll experiment with adding some=20 output load, otherwise I'll have to order some tantalums. Thanks, -Neil. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .