I just got a second hand fluorescent light ceiling fixture. Very pristine condition externally, both the fixture and the external electronics. Certification marks are in place, and it's manufactured by a known and trusted manufacturer. I was just detaching the small plug from the end of the cord, when I noticed that the inside of the plastic plug case has a small lichtenberg figure, e.g. a singed lightning mark. It's a surface mark that hasn't corroded or greyed out the inside of the case in a general sense, it's more like some lightning lines about the strength of a lead pencil mark. No detectable smell. No flickering or buzzing of the light when I tested for a short while. The wires seemed to be connected alright. By the looks of it, the mark is not one of subsequent sparks but a one time phenomenon. Is this normal or should I worry?
It's not a sign of any sparking or other high-energy phenomena (as it would melt the plastic). It's merely dirt accumulating on the plastic in curious pattern. You can wipe it off or ignore. It's not an electrical issue, it's rather property of the material.