Disclosed is a power assembly for supplying electrical power to 4-20 mA 2-wire field devices, including HART-enabled, short run Profibus PA, and Foundation Fieldbus protocols. A preferred embodiment of the power assembly is designed to simplify the testing, troubleshooting, and configuration of HART 2-wire field devices. The disclosed device is compatible with hand-held or PC-based configuration software, and utilizes the available power from the USB port of a laptop, or any other compatible source of low-voltage DC. An internal circuit converts the low voltage DC to 24-volt DC to provide 2-wire power for the field devices. The power supply includes the necessary network communication load and/or resistance and may provide a quick modem/network interface and/or milliamp meter connection. All the necessary connections to the 2-wire field device are made with a single pair of quick-disconnect fittings.