The circuitry for decreasing voltage for the DAA in modern modems is called a voltage regulator. They've been around for years, and USR uses TO-220 packages, not those damn tiny things. I think the average hobbyist could replace it if he could solder. You'd have to remove the old one, decode the part number to figure out which rating it is (Can't be too hard, every USR I've ever seen used Motorola regulators), buy a new one from Radio Shack for $1.39-1.99 depending on where you live, and solder it on.
Lincoln
January 2005