The problem is most likely the Z-chip got fried and will need to be replaced. The early models of the MH the chip was in a socket and could easily be replaced. Newer models the chip is soldered in, still replaceable, just not as easy. The chip is a simple op-amp and can be found from several online electronic stores. Do a search on here for Z-chip, we just had this discussion about a week ago. You'll find all the details you need.