Noisy Coil (inductor)

[hpibmx]

Hi,
I’ve come across few motherboards iPad and a laptop.
Right after power on I can hear very small noise sound, found out when coil windings get lose they start making noise when current passing through them.

So my question is how can I spot one? I’ve more than 20 in the iPad motherboard. Is there anyway I can find out which is making this noise?

Thank you in advance.

[amyk]

Stethoscope. You can make a usable one out of a rolled sheet of paper.

[EEEnthusiast]

By touching them. The noisy one will get a bit quiet, once you put your finger on them. I guess if they are making enough audible noise, then they are big enough to touch them one by one.

[jonpaul]

Poor SMPS stability and subcycle oscillation.

Due to sloppy Chinese design

j