Power Brick really hot and making noise

[crspechicn]

Have troubleshooted switch-mode supplies before, noise is not always normal, especially in higher end devices like Apple power bricks. I have had several of these, and have never heard any noise emitted from any of them. While it is possible for switchers to make audible noise, I wouldn't think it is a normal thing in this case. I would take it in to Apple and see what they say.

 

[Big-TDI-Guy]

In the morning.

Hmmf, so much for the Book of Knowledge(TM) - "laminations of the coil".
It probably meant to say "laminations of the transformer" (in a typical flyback design).

Actually large valued ceramic caps also make noise (the ceramics are slightly peizoelectric), in the audible range. I've had 22uF units "sing" in the lab (6-11kHz), even with relatively minor voltages across them.

If it's normal? Well I have heard othewise good power supplies do this - but I've not noticed it from my 85W MBP PSU.

A lot of switch-mode supplies I've worked on had more inductors than transformers - and most of the high-frequency / current areas involved inductors. I'm willing to guess the Wiki article was likely referring to coils in general. You don't need an iron core or a second set of windings to generate sound, even had small air-core inductors generate audible ringing.

I've had non-ferrous metals, optical crystals and even liquids generate noise from electrical currents. Bearing in mind, none of these components were intended to generate acoustic noise in the first place.