On Wed, 29 Aug 2007 03:57:37 GMT, Ross Herbert
wrote:



Magnetostrictive squealing often occurs in SMPS when either the
windings on a core are not tightly wound or held to the core with a
dampening compound. Also, in a ferrite transformer using E-I or
similar cores, unless the segments are properly fixed or glued
together the interface joints will allow minute movement at the
resonant frequency (or sub-multiple) of the SMPS thus resulting in
squeal. The only
solution is to remove the transformer and heat it to soften any
adhesive and then take the core apart, clean the faces and then
re-assemble under pressure using a good quality cyanoacrylate
(superglue).