As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TROUBLESHOOTING FOR ALTERNATOR NOISE, INSPECTED ALTERNATOR AND FOUND BOLT LOOSE INSIDE ALTERNATOR CASE. REMOVED ALTERNATOR AND DISASSEMBLED, FOUND DIODE RECTIFIER BRIDGE BOLT HAD BACKED OUT AND HAD CONTACTED THE ROTOR, BENDING THE BOLT AND ELONGATING THE MOUNTING HOLE ON THE RECTIFIER BRIDGE.