Not necessarily. In the olden days, chargers used selenium rectifiers (and before that, I suppose tubes, though I've never seen one). This one could be from the era when the switch was being made to silicon and manufacturers were proud of using the latest technology. Yeah, strictly speaking, selenium is solid state too, that is, not a vacuum tube, but the term didn't come into use until the advent of silicon and germanium diodes, transistors, and the like. That's why I advised checking the weight of the unit. One of the primary benefits of switching supplies is that the transformers are tiny and light.