Abstract: A compressed air supply assembly for operating a pneumatic assembly includes a compressed air supply; a compressed air connection to the pneumatic assembly; a purge connection to the environment; a pneumatic main line between the compressed air supply and the compressed air connection comprising an air dryer; a purge line between the compressed air connection and the purge connection; and a solenoid valve arrangement with a control valve to control a purge valve. The control valve is connected to a control valve connection in a pneumatic control line connected to a pressure control connection of the purge valve, and the purge valve is connected to a purge valve connection in the purge line. A pressure-maintaining device is connected to the pneumatic control line and maintains control pressure at the pressure control connection when the purge valve connection is open, independently of pressure in the purge line and/or the main line.