How To Quiet PC Power Supply--Not a Fan Problem

A carefully placed, non-conducting rod (a thick wooden stick will work) gently pressed on the PS's components one at a time should find the problem. More than likely it's one of the toroids. Put a small dab of silicone at the base where it meets the board.

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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 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).

squeal. The only

I know I rebuilt a transformer using shellac, but I think there is better stuff out there. Shellac also absorbs water when just setting around. It might initially dry quicker than a varnish.

greg