Not being game enough to DIY it  (as suggested in some answers to [this question][1]) I've bought a 240V charger for my beard trimmer. Despite the singular "240V" listed on the label, the person at the other end of the Wahl support line insisted that it will work on 110V in the US with only a pin adapter, but the original charger (rated for 120V, left) would not work here in Australia on 240V.

![enter image description here][2]

I find it quite surprising that the 240V charger would in fact be "world compatible" and not labelled as such. Is it inherent in the nature of switching power supplies that one rated for 240V will work when presented with 120V but the converse would not be true? What are the odds of the magic smoke leaking out if I plugged the one rated for 120V into a 240V socket via a pin adapter?

  [1]: https://electronics.stackexchange.com/questions/33675/how-can-i-charge-my-beard-trimmers-li-ion-battery-from-usb
  [2]: https://i.sstatic.net/cOZje.jpg