Disclosed are exemplary embodiments of sub-base assemblies for substrate-mountable devices and related methods. In an exemplary embodiment, a sub-base assembly includes a cover, a base, and a circuit board having a plurality of wire terminals for receiving wiring passed through the base and circuit board. At least one light source is mounted on the circuit board and is operable, before the wiring is connected to the wire terminals, to direct light toward the wire terminals through the base.