I'm told changing it voids warranty, but ymmv. Also, the guy who took these shots said something about the Drobo using a different power connector, which required either splicing some wires differently or making a connector, or some such jazz.
I forget the specifics, but I think I have it bookmarked at work, and I'll post the link here tomorrow. It took a while to find for some reason, not too many internal Drobo pics out there....