Help with broken dimmer lamp

[Rocky]

Folks, I have a floorstanding lamp with two bulbs (a top light and a smaller booklamp lower down, you've probably seen lamps like it, they are quite common) dimmable by two control knobs. No light came from it and changing fuse didn't do the trick. It's an expensive lamp and I didn't want to discard it, so I opened it up, and out came a ratnest of wiring and a PCB with multiple coils, some regulators, some resistors and diodes and another fuse (inaccessible from the outside) marked 250VAC. I measured the terminals coming from the net power and found them to have expected VAC, then turned the knobs and measured the outputs (to the lamps), nothing. So I shorted the fuse and out came the light. Now, this would be just great if it weren't for a hissing noise (hzzzzz hum!) coming from the PCB (from a coil I suspect but I could't pinpoint it). The hiss is very apparent at low light settings (for the book lamp, the top light doesn't work as the bulb is dud, but terminals measure OK), when I turn the knob for higher light intensity the hiss goes down. Now, my question is;

Can this be caused by a damaged coil? and if so, does anyone have a good idea on how to pinpoint wich coil it is, so that I can replace it?

EDIT: I do remember the lamp made this very same hissing noise a short period of time before it went dud in the first place.

[Rocky]

nt.

[pinkmouse]

Firstly, shorting the fuse is a bad idea. Secondly, the noise you are hearing is the switching of the triac, this means that some of the filter components are faulty. Unsolder one end of all the chokes and check for continuity. If one is open circuit it will need replacing. If none of the chokes have a problem, it is likely to be a cap. These are cheap enough just to do a blanket replacement of them all rather than try and find the faulty one.

But to repeat, don't run the amp with anything but the correct fuse, you could kill yourself or another.