I have a PC Engine Duo (not duo r) with the stock 100v power supply. I am not sure if it is safe to use in a USA household or if I should buy a step down converter. Will it be harmful to the unit to give it a 120V input? I know Japan is half 100v half 120v after all so it would not make a lot of sense to me if it did not work on 120v power. But i want to make sure first so I don't damage it.
That is safe to use in the USA. I use a lot of original Japanese power supplies for my Japanese consoles in the US.