As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DECLARED EMERGENCY-----------------------------------------DEPARTING FL390 CABIN ALTIMETER HORN AND LIGHT CAME ON FOLLOWED QRH & QRC CABIN ALTITUDE WAS CONTROLLABLE NO DISCOMFIT NOTED BY CREW AND PASSENGER. / R&R #2 ENGINE HIGH STAGE PRESSURE REGULATOR PER AMM.