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I have a receiver and it's SMPS board is making a constant hissing sound which is noticable from a few steps away, so I'm sure it's not normal. The source is probably the ferrite transformer on it, but I'm not 100% sure because it's hard to tell. What components are the most likely to cause this problem (and why)? Because they all measure ok, but I only tested them with a multimeter and in circuit. Or what can I do with the transformer if that alone is responsible for the noise? The noise is there whether or not the SMPS is loaded, there is only a little difference. The schematic is here (page 112): https://www.manualslib.com/manual/950375/Denon-Avr-3311ci.html?page=112#manual Should I just change all electrolytic caps and hope it will go away? If not, then what?

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  • \$\begingroup\$ If there are ceramic capacitors, they can do this due to piezoelectric effect. \$\endgroup\$ Commented Feb 20, 2021 at 15:18

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The noise comes either from the ceramic caps (due to piezoelectricity) or magnetics (due to magnetostriction). If it's the caps, you could change them for flexible termination ones which are designed to prevent vibrations from propagating to the board. If it's the transformer, you're screwed.

The document linked in the question does not mention how much current this power supply can output, but a 5V 50W power supply of good quality costs about €20, which means replacing the whole board may be a reasonable option.

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