Smothering them in epoxy might have helped.. I'm shocked that some new
MBRDs may have this problem . It's scary buying a MBRD thinking it may
have that problem, and it not being documnted.
Howcome old MBRDs didn't have that problem?
Different rail voltage, different frequency switching of the
fets before the inductors, different current, higher
voltage. All combine to result in a frequency more likely
to approach the resonant frequency of the inductor.
Not all samples of a given board may have the problem
either, depending on the load (parts plugged into it),
random load of inductors used (remember we aren't
necessarily talking about boards made with *premium* parts,
it would be prohibitively expensive to make a motherboard,
PSU, etc, out of such parts. It's a bit of a wonder they
can even make a working board for under $75 when you
consider all the work, parts, and followup support that has
to go into it.
Some Televisions are horrible culprits of high pitched whining noises..
So bad that I doubt opening them and using epoxy would help much!
If you can get at the coils that are whining, fixing them in
place will solve any such whining on anything. Single layer
inductors are a bit easier, the epoxy doesn't have to seep
in to get to the inner layers so more often a soak in
varnish/whatever could be needed.
Ideally, one would want to not be unlucky, and so get a computer
without transformers emitting a high pitched noise.
Agreed, but practically any system has some flaws, this one
can be more annoying than many but at least there is a way
to fix it (unless part of an integrated network socket, but
someone intent on fixing that could replace the whole socket
assembly I suppose, if they can source a replacement (and it
might not be cheap, I've never tried to source one).
note: anybody here hasn't heard of epoxy, wikipedia seems to have it as
a glue that is an electrical insulator / non conductor. Can be used in
electronics to cover components to prevent shortcircuits. ... And
apperently, to quiten them if they whine!
Plain old glue would work too, just as long as it's
electrically non-conductive and not terribly magnetic, and
of course heat resistant. With epoxy you don't have to
worry about it melting but if it were to get too hot, it
might get brittle and since an inductor would inherantly
expand and contract with heating & cooldown, the epoxy could
come off.
Above I mentioned "terribly magnetic", I don't even know if
there are any epoxies terribly magnetic, unless it was
something special formulated specifically to be such. I
have on occasion mixed metal particules into epoxy to
fortify it (different use, not inductor related) but
generally even some common epoxies like JBWeld have some
(iron?) in them and I have successfully used JBWeld to quiet
inductors.
Superglue/cyanoacrylate might work too, I think some
formulations are rated to 150C temp, but a bit too thin to
fill gaps in an inductor (esthetics really, I would try to
keep the goop on the inductor instead of having it run out
onto the motherboard), and I don't know if any (let alone
all) of the thicker gel type superglues have the same temp
ratings. IOW, epoxy works so I continue to use it.
