I'm trying to fix my Lupine lights - broken bit of wire, fair enough. However on one of the cables under the insulation it seems to be full of black powdery stuff. I've seen corrosion before, greeny bluey grey stuff, but only within a few mm of a break in insulation. Here there's no visible break and it seems to be the whole way along. I've cut off tons of cable. I've also seen white powdery stuff in cables before, some kind of mineral for something.
Problem is I can't tin the thing cos of all the black stuff. It's really pissing me off, now I can't commute tomorrow cos I've got no lights.