As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR TURN BACK. FLIGHT CREW REPORTED 30 TO 40 CHIMES FROM BACK OF AIRCRAFT. COULD NOT TALK TO CREW, INTERPHONE INOPERATIVE. REPLACED PA AMPLIFIER AND SYSTEM CHECKED OKAY. ALSO FOUND PILOT CALL SWITCH ON FWD ATTENDANT'S PANEL BAD, CAUSING PILOT CALL CHIME WITHOUT BEING PRESSED. REPLACED FWD ATTENDANT'S PILOT CALL SWITCH AND SYSTEM CHECKED OKAY.