First thing is get/build a light bulb limiter. I don't know the particulars of the 700RB but check for a big DC voltage on the output. There are probably one or more shorted output or driver transistors that can be found with an ohm meter. Also, ohm any "sand box" resistors as these usually go when a transistor shorts. If any of this is over your head and you are not familiar with sourcing and replacing transistors, I suggest you take the amp to a tech for repair.