I got the new parts today. Redux:
Adding 100uF electrolytic, swapping in 10u 25v 1206 ceramic did NOT get rid of the buzzing, just reduced it a little. Swapping in 10u 16v 1206 tantalum with the 100u DID get rid of the buzzing, both the low pitch and high. There's still 80mV P-P spikes on the line[*] at 8.3KHz (line refresh rate) but that's 6X better than the 500mV ripple it used to have. Lesson: for heavy-noisy loads at audible frequencies, you need sufficient non-ceramic decoupling before (or instead of) the ceramics. [*] http://www.delorie.com/electronics/alarmclock/ _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user