As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ALTERNATOR SHORTED INTERNALLY IN-FLIGHT CAUSING SMOKE IN COCKPIT. PILOT MADE EMERGENCY LANDING. INSPECTED AIRCRAFT, FOUND ALTERNATOR OUTPUT TERMINAL SHORTED TO GROUND. THERE IS NO CIRCUIT PROTECTION ON ALTERNATOR OUTPUT CIRCUIT. THIS CAUSED WIRING TO BURN UNTIL PILOT SHUT OFF BATTERY MASTER. REPLACED WIRING. INSTALLED CIRCUIT BREAKER IN ALTERNATOR OUTPUT CIRCUIT.