Power supply for retrofitting interior lighting 73410 and 73411, consisting of an axle bearing with a soldered cable and socket, as well as an axle bearing with a soldered cable and plug for electrical connection. Usable for the four-axle express train cars of the standard design from 1928 to 1930, with symmetrical bogie mountings. With this power supply, for example, the Märklin express train cars 42500 to 42540 can be equipped with LED interior lighting using the corresponding DC wheelsets.