Well, I just now disassembled the electrical connections (in the handle) of my DeWalt joiner, to see if a USA version can be switched over for 240V operation -- the switch inside has both voltages marked on it, but I didn't see any way of converting the wiring over, so nogo.

As for the one you have now, there should be three (3) adjustment knobs in total, I believe. So, do the obvious and make sure you're "locking" it with the correct knob!

Cheers