On Sep 13, 2007, at 12:55 AM, DJ Delorie wrote: >> Is it convenient to try putting an choke in series with the OLED's >> power supply line, with the OLED's bypass capacitor on the OLED side >> of the choke? > > Hmmm... 100uH power inductor, no change.
Crap. :-( >> I've only used those two methods, aside from probing around with >> an oscilloscope to look for the noise. One other trick that I've >> not tried (if anyone can comment on this I'd appreciate it) is to >> use an inductive pickup probe to look at the *current* waveforms on >> the supply lines to different parts of the circuit, and see what >> corresponds to the noise you're hearing. > > I don't think my parallel-port scope is sensitive enough for that. > Plus, anything with a coil just picks up magnetics from the switcher's > inductor, but the switcher isn't the supply that provides the +12v. True. :-( You might be able to temporarily shield that inductor, but that's a shot in the dark. >>> 2. What kind of components *can* make that kind of noise? >> >> Inductors and PCB traces, mainly...but I suppose nearly anything >> probably could, to one degree or another. > > PCB traces? Yes, they can actually resonate. I know you've been working with desktop computers for a very long time (I used DJGPP in ~1992)...have you ever noticed a "squealing" sound coming from a machine when it's busy, changing with processor activity? Sometimes that's the power supply, but it's usually traces on the motherboard. -Dave -- Dave McGuire Port Charlotte, FL Farewell Ophelia, 9/22/1991 - 7/25/2007 _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user