As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE FLIGHT, SMOKE FILLED THE CABIN. ELECTRICAL POWER WAS TURNED OFF. SMOKE CLEARED FROM CABIN. INVESTIGATION REVEALED THE PROPELLER SYNCROPHASER CONTROL BOX HAD SHORTED AND EMITTED SMOKE. THE NUTS THAT HOLD THE CANNON PLUG PINS HAD VIBRATED OFF AND SHORTED THE CIRCUIT BOARD.