I posted a few days ago about my mum's (er, and dad's, of course) washing machine. It was making a loud strange buzzing/squeaking noise every now and again. Quite hard to describe, but it sounded electrical, rather than mechanical. Magnetostriction springs to mind, but I've never heard it so loud. It sounded like it was coming from the area of the controls, so I thought I'd take the top off, get me mum to wash something, and look for sparks.
Anyway, once the top was off, I had a quick look at the PCB, and noticed some carbon dust had collected around a small transformer. My first thought was that it was faulty, but then it occurred to me that the transformer may just be attracting the dust into that area, and that it was the dust itself (being conductive) that may be the problem, since it was in a high voltage area of the board. I brushed and blew the dust away, and amazingly, the problem seems to be fixed. Although, of course, just taking out the PCB and putting it back may have also fixed some small mechanical problem.
I was just wondering if anyone could confirm for me that a build up of carbon dust on a PCB could actually cause such a strange loud shrieking noise?