A wee part of a power supply from a very large (professional) printing machine.

Was asked by a work colleague to have a look at this. This blackened area around the incoming mains was the first thing to catch my eye. And I expressed my surprise at seeing that there must have been some sort of hefty short-circuit between the live (at the fuse) and the chassis. A big enough short to cause the metal on both the fuseholder and the chassis to be vapourised. Said colleague then reluctantly confessed to having had a look, and had been testing the fuse whilst the unit was live. The exposed part of his tester's probe had touched both, causing the short... wrecking the probe, and tripping out the power for the whole  building in the process. It was then he decided it was perhaps best to call on someone that specialises in stuff like this...