My 5501 has the same configuration as Jan's, and I am unable to notice any noise at all. The last time I checked my hearing it went up to 18kHz in the good ear. So I am having difficulty understanding why Jan is experiencing this noise and especially noise at such a high level. And the fact that this is occurring in more then one unit that Jan is working with, makes this much more difficult for me to dismiss.
One question is what power adapter is being used and what are it's ratings for voltage and current. And, more specifically, are all the adapters the same (for all the 5501 units that are emitting noise)? Also, are they regulated adapters or unregulated? When I am faced with something that is behaving in ways that I can't understand, I sometimes try changing something. If we are correct in thinking, that this noise is caused by one, or both, of the two switching-mode power converters in the 5501, why not try changing something connected with them. One thing we could change is the input voltage that is supplied by the external power adapter. The specification for the 5501 gives the input voltage range as 6-25 Volts. Why not change this voltage and see how this effects the noise. The other idea is to change to load. Perhaps if the load was increased or decreased the noise would change. One way to increase the load would be to place an additional load on the 3.3V or 5.0V regulators. This can be done by attaching resistors of appropriate value to pins of connector J-5. All of these suggestions are based on the assumption that the noise is connected with the operation of the 3.3V or 5.0V regulators. -- Gavrik On Sun, Jun 17, 2012 at 6:21 PM, Christopher Hoover <c...@murgatroid.com>wrote: > check any SMPS sections. > > > On Thu, Jun 14, 2012 at 9:58 AM, Jan Ceuleers > <jan.ceule...@computer.org>wrote: > >> On 06/10/2012 08:15 AM, Jan Ceuleers wrote: >> > Hi. >> > >> > I've been using net4801s and a net5501 as broadband routers for use at >> > home for some time now. >> > >> > Generally great and fun. There's just one down side: these boxes are not >> > completely silent, in that they make a strange hissing sound while >> > they're doing actual work (like routing network traffic). >> >> So, after a few days here's a summary: >> >> > So here's a sanity check: are my boxes the only-ones doing this? >> >> Apparently so, because nobody said that they are also experiencing this. >> >> > What's causing it? I thought it was the CPU but given that the 4801s and >> > the 5501 have a different CPU (OK so they're both Geodes) I was thinking >> > perhaps not? >> >> There seem to be two camps: some say capacitors and others say coils. >> >> > Is there anything I can do to stop the hissing? >> >> The consensus of opinion here seems to be to pot the components in >> question, possibly using hot glue. >> >> (BTW: "boxen" is the correct spelling). >> >> Thanks, Jan >> _______________________________________________ >> Soekris-tech mailing list >> Soekris-tech@lists.soekris.com >> http://lists.soekris.com/mailman/listinfo/soekris-tech >> > > > _______________________________________________ > Soekris-tech mailing list > Soekris-tech@lists.soekris.com > http://lists.soekris.com/mailman/listinfo/soekris-tech > >
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