What was found
(CAN) ON JULY 17 2009, ACFT INBOUND, PILOTS REPORTED THAT LT AC BUSS FAILED CREW LANDED WITHOUT INCIDENT. MX CHECKED OUT SYS LT AC SYS AND COULD NOT DUPLICATE PROBLEM AND REPLACED LT INVERTER FOR PRECAUTIONARY REASONS AND SYS CHECKED OUT GROUND SERVICEABLE AND DISPATCHED. ON INBOUND FLIGHT, PILOTS REPORTED LT AC BUSS HAD FAILED AGAIN ACFT WAS SWAPPED AND BROUGHT TO HANGER. MX FOUND A HARD FAULT ON THE LT AC SYS, TROUBLESHOT SYS FOUND THAT C/B REF DESIGNATOR (CB213) PN (7277-2-10) FOR THE 115 VAC OUTPUT HAD A INTERMITTENT INTERNAL OPEN WITH VIBRATION AND LT INVERTER PN (SPC10) HAD FAILED. C/B (CB213) PN (7277-2-10) REPLACED WITH LT INVERTER PN (SPC10), ACFT GROUND CHECKED SERVICEABLE AND DISPATCHED WITHOUT FURTHER PROBLEM.