As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ALTERNATOR DRIVE COUPLING FAILED ON LT AND RT ALTERNATORS, IN IMC SIMULTANEOUSLY. 1 PIECE COUPLING WITH A RUBBER LORD BUSHING BONDED/INTERFERENCE FIT SLIPPED, CAUSING THE ALTERNATORS FAILURES. PILOTS LOST ELECTRICAL AND DESCENDED THROUGH ICE, UNABLE TO SHED MODERATE TIME ICE ACCUMULATION. TOTAL COMM AND AVIONICS FAILURE, PARTIAL PANEL WITH NO PITOT HEAT AVAILABLE.