UV hard-surface disinfection system that is able to disinfect the hard surfaces in a room, while minimizing missed areas due to shadows by providing multiple UV light towers that can be placed in several areas of a room such that shadowed areas are eliminated and that can be transported by a cart that is low to the ground such that the towers may be loaded and unloaded easily by a single operator. A power amplifier is provided with first and second switching devices and an inductor connected between the switching devices. A mechanism that rotates a turntable of a media cartridge picker is also used to move the drive shaft unit such that the drive shaft unit is selectively coupled with either one of the first or second media cartridge transport magazines.