DJ - On Thu, Sep 13, 2007 at 12:34:38AM -0400, DJ Delorie wrote: > It's really hard to tell which part is doing it, just from listening. > The sound may be a combination of a high pitch whine and a 100hz buzz > (the oled is 100hz). > > I *think* the sound may be coming from the switching power supply (it > has three power inductors in it), but neither the +15v power input nor > the 3.3v rail have any noise on them (outside of the 150KHz from the > switcher itself). Bypassing two of the inductors (the filter ones) > does nothing. Pressing on any component does nothing. > > 3. If you know what's causing it, how do I fix it?
A lot of switching power supplies have a low-current mode where they don't switch at the full rate. Those modes tend to be noisier, both electrically and acoustically, than the normal fixed-frequency mode. If that's the culprit, most switching controller chips have a control pin to disable it. They don't make it the default, because it decreases efficiency. - Larry _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user