What was found
IAH - FLIGHT 2738, THE CREW REPORTED THAT THE CAPTAINS BOOM, HAND, AND O2 MASK MICROPHONES WORK INTERMITTENTLY. THE AIRCRAFT RETURNED TO IAH WHERE IT LANDED WITHOUT INCIDENT. MAINTENANCE REMOVED AND REPLACED THE NUMBER ONE COMM/XPNDR UNIT (RCZ), OPERATIONALLY TESTED WITH NO DEFECTS WITH NO DEFECTS, AND THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE.