I have a copy of the Service Notes as well. I'd offer to troubleshoot it for you, but since you haven't mentioned what, exactly, is wrong with it, I can only imagine that it's in some sort of horrible, disastrous state.

Unless it's something easily fixed (again, lacking details), my suggestion is to call the Roland US support line, get an RMA, and send it to them to repair. Last time I checked, the hourly labor rate was around $80, which is a lot, but still less than you would spend replacing the unit. One additional benefit to having them do the work is that you can request that they install the latest ROM (1.02 for the CM-500, I believe), which they ought to do for no charge.