For what it's worth- if the transformer is still MIA, we have some apartment buildings from the 40's-60's (all different build years) and we've had them all over as many have said. In the attic of our current building we're working on, all 4 units' wires come together at a single area, so you might check your attic. Also, my dad has heard of them being placed (somewhat commonly) inside cabinets (like the kitchen, usually the upper ones) so that's another possible spot. Good luck!!