You can install an US (or any NTSC) motherboard in a European Apple but
there are some things to consider (directions like "left" or "up" are
based from looking from the keyboard end of the board):
- The power supply should be no problem as the connector is in the same
place and uses the same voltages.
But:
- The cable to the keyboard will be too short because the connector is
located higher up on an US board.
Easy solution: Manufacture one yourself from an old PC floppy or
harddisk cable and the original connectors.
- You will also have to extend the cable to the speaker as the
connector sits on the lower right of the US board and not near the
speaker.
- *If* you have a keyboard with special characters (and don't want a
permanent US-only keyboard) you may have a serious problem.
This is because on an US board you'll naturally have an US keyboard ROM
and an US-characters-only video ROM.
You can replace the keyboard ROM with your original ROM as its pin
compatible but this doesn't work with the video ROM (the US ROM has 24
pins whereas European ROM has 28 pins).
Solution: Buy a video ROM adapter from Bill Garber/GSE, install it in
the US board, insert your original video ROM and connect the switch
under the keyboard to it.
This is a clean way as it can be undone with no problems and doesn't
need soldering.
Additionally:
You also may have to consider that the aux-slot is not in line with
slot 3 anymore!
This can be a problem with certain expansion cards (special European
video and RAM expansion boards that need both slots in line).
On the other hand you'll probably gain a slot because on the US board
the aux slot is on the far left and slot 3 isn't blocked any more.
I successfully converted a German and a French Apple with this method
so I don't think that you'll have any further problems (provided that
the US board is in working condition).