A field replaceable power supply cartridge is provided for coupling with a socket. The cartridge has a latch mechanism that can be actuated by the user to couple the cartridge to the socket, such that latches of the cartridge releasably engage recessed portions in the socket. The cartridge has a key feature that corresponds to a key feature on the socket, allowing the cartridge to be coupled to the socket in only one orientation, thereby preventing the incorrect electrical connection between the cartridge and the socket. The cartridge can have a multi-pin electrical connector for coupling to a corresponding connector on the socket. The socket can be a relatively short socket, where the electrical wires are bottom fed, or can be a relatively tall socket, where the electrical wires are side fed via one or more openings in the body of the socket.