What was found
(CAN) IN CRUISE, EICAS MESSAGES AC BUSS 1 AND AC UTILITY BUSS 1 APPEARED SIMULTANEOUSLY WITH A CHATTERING NOISE WHICH COULD BE IDENTIFIED. THE AIRCRAFT LANDED AS SCHEDULED. INSPECTION BY MAINTENANCE REVEALED THAT: C/BS J4 CBP-1 AND 2 (AC UTIL CONT) AND C/B A2 CBP-1 WERE POPPED OUT. THE AC UTILITY BUSS 1 CONTACTOR 1K4XD WAS ALMOST COMPLETELY MELTED. THE PANEL ASSY, THE OTHER 3 RELAYS (K1XC, K2DB, K3DB) AS WELL AS SOME WIRES INCLUDING THE FEEDERS HAVE BEEN DAMAGED BY HEAT. ALL DAMGED PART WILL BE REPLACED.