Dafydd: I'm afraid I don't remember exactly where all the charges were, but as far as some of the other puzzles here are some spoilers.
The Conductive Plates:spoiler:You find the plates in the room the Mechanist is guarding after the room with the paintings. If you want to loot the paintings room, you pretty much have to take out that guard. Anyway, when you take the paintings, the golden heads activate and start spitting arrows at you. However, if you replace the paintings with the plates as you go, the heads never activate.
The 'Zapping' Urns: spoiler:The room on the right after the Death Ward room. There are two pedestal-type dealies with four circles. Look behind them.
EDIT: didn't see that Nightwalker had already addressed the Death Ward one.