The fuse is going to be where the power plug comes in could be standard glass fuse or a poly fuse, which look almost like minature batteries, or resistors without normal colour codeing, that's the only place it's fused, if you bumped an internal connection the fuse would likley not have blown, even a dead short on an IC on the motherboard won't cause the fuse to blow but could easily over voltage an IC to the point of a silent failure. Also, since you're getting a RROD, you know the fuse isn't blown.