As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) ON DESCENT, SMOKE NOTED IN AFT CABIN FOLLOWED BY AIR CONDITIONER CIRCUIT BREAKER TRIPPING. INSPECTION SHOWED THAT THE LEFT MIXING VALVE HAD INTERNALLY SHORTED ITSELF TO GROUND DAMAGING THE PRINTED CIRCUIT BOARD ON CABIN TEMPERATURE CONTROLLER. THIS WAS CAUSE OF SMOKE.