SYSTEM - CHANGE OF THE POWER SOURCE TO THE RECOMMENDED PRESSURIZATION SYSTEM CIRCUIT BREAKER. SERVICE BULLETIN MOS 06-JAN-2011 SB 737-21-1178 AIR CONDITIONING - FUGHT COMPARTMENT CONDITIONED AIR DISTRIBUTION - CHANGE OF THE DUCTS AND RECOMMENDED PLENUMS TO REDUCE NOISE. SERVICE BULLETIN MOS I9-AUG-2013 SB 737