UNUSUAL ELECTRONIC TICKETING IN AFT GALLEY AREA.

Narrative

BEFORE DEP AT PHL; FLT ATTENDANT NOTIFIED ME OF UNUSUAL ELECTRONIC TICKETING NOISE IN AFT GALLEY. AFTER FO AND MYSELF COULD NOT IDENT THIS; WE CALLED MAINT. THEY COULD NOT IDENT BUT SAID IT WAS STRONGEST IN AFT BAGGAGE COMPARTMENT. AFTER REMOVING PANELS DISCOVERED SOUND CAME FROM SWITCHING UNIT ON THE MAIN OUTFLOW VALVE. SOUND WAS RHYTHMIC AND SOUNDED LIKE A WARNING ON DISTANT TRUCK OR MACHINERY BACKING UP. SWITCHING WAS ALSO TOO HOT TO TOUCH. TECHNICIAN SAID ALL THIS WAS NORMAL. COULD THIS INFO BE PASSED ON TO BOTH THE CABIN AND COCKPIT CREWS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: ON CALLBACK THE RPTR REVEALED THAT HIS REASON FOR SUBMITTING THE RPT WAS THAT BOTH HE AND THE FLT ATTENDANT THOUGHT THAT THE NOISE WAS UNUSUAL; NOT HAVING HEARD IT BEFORE. HE WAS NOT KNOWLEDGEABLE ON THE COMPOSITION OF THE PANELS THAT ADJOINED THIS OUTFLOW VALVE AREA IN THE AFT BAGGAGE COMPARTMENT. HE HAD TO RELY ON THE SUPVR AT THEIR MAINT BASE THAT 'THIS WAS NORMAL;' MEANING THE SOUND AND THE TEMP OF THE UNIT. RPTR IS GOING TO ASK HIS SUPVR IF ANYTHING HAS BEEN DONE WITH REF TO NOTIFYING FLCS OF THIS SIT. HE DIDN'T KNOW IF THE MAINT BASE COULD GIVE HIM ANY FURTHER INFO. MAJOR CONCERN IS WHETHER THIS WAS AN ACFT MAINT DISCREPANCY AND IF A TELEPHONE DIAGNOSIS OF THE EQUIP IS THE CORRECT PROC.