This 120V AC power source is built with a simple 120V:24V or 110V:24V center-tapped control transformer and four additional component ... use larger transformers and transistors. This type of 12V ...

There’s a big transformer taking up half of the footprint. This steps down mains voltage to something a 7824 regulator can handle. That’s a 24V linear regulator which is fed by a bridge ...