gEDA-user: buzzing board

[John Coppens]

On Thu, 13 Sep 2007 11:38:57 -0400
DJ Delorie <dj at delorie.com> wrote:

> > Did you cheap out on the inductor?
> 
> Not that I'm aware of.  I used these:

By far the most probable cause is the inductor. I've made quite a few
switchers, and several of them caused problems. I'm not so preoccupied
with the noise by itself, but more by the possibility this may cause
chafing and shorts on the long haul.

The buzzing may appear only if a certain load (lower _or_ higher) is
placed on the supply, as the switcher frequency passes through some
resonance in the windings (even they should ideally be impregated). Even
'fixed frequency' switchers vary a little...

John