I did some checking on a jbo1 which was having similar problems. One issue I discovered was what appears to be a blown fuse that was built into a small circuit board at the very bottom of the whole unit. When I hooked up a jumper across the two contact points everything fired up just fine. However, that just made it so the motor would run; the actual shreader heads still weren't turning and the whole thing was making some kind of grinding noises from somewhere further down the drive assembly. When I took apart the upper assembly -- you know, the big thing with all the motor and grinder and cogs within it -- I found one cog with a a couple of teeth broken off and another smaller one that didn't have any teeth at all left on it. If I can find replacements for those (they just slid right off their axles), I'm guessing the whole unit would be operational again. I'm not sure if that's gonna be worth the effort, but we'll see. I'm just doing this for a friend of mine who asked me to see if I could figure out what was wrong with it, so I'm not sure if she'll want me to go ahead or not. Good luck on yours.
Junkboxjim
April 2011