Yeah, after starting to go through the rest of the schematics I realized that all of the chips on the board use only +5v, and the rest of the rails are just passed through to other components (expansion slot, floppy drive, etc). And correct, there's no boot chime.
I tested all of the pins on the ROM SIMM slot to the muxes (D4 through D19, and UJ2/UI2/UJ3/UI3), continuity good there. I'll look closer at the C12 area, and after that, go back to the ROM muxes and keep testing forward from there. I'm also planning on giving the board a good soak in IPA, since all I've done so far for c