The power amp module is custom built for Fender, and is also the main power supply for the amp. It sits on the bottom of the cabinet behind a metal grill Faraday cage.
Thing is, if that module died, it's basically impossible to get a replacement
Your best bet is a warranty claim with Fender methinks.
Other than that, both the FR-10 and FR-12 are biamped, meaning there's no crossover in place if you want to turn them into a normal cab.