Updated Nov-2013
I'm a proud owner of this Bosch IXO IV screw driver, that I bought in the Netherlands. I recently moved to the US and it doesn't charge from the 120VAC mains
The IXO base has a 230VAC transformer, a rectifying bridge, a electrolytic capacitor and a series diode and outputs 7VDC/250mA according the specification.
I decided to built in a power jack socket for a wall wart power adapter. I connected the wires in between the rectifier bridge and the series diode.
From the side the power jack socket looks like this.
I connected it to a 7VDC wall wart adapter and it's happily charging!