What was found
ON DESCENT, ENCOUNTERED BUSS AC 1 OFF AND LEVEL 2 SELECT FADEC ALTERNATE. RAN FADEC CHECKLIST AND SELECTED ALTERNATE ON ALL 3 ENGINES. OTHER ALERT ON ELC SYNOPTIC WERE (AC T/E OFF, EMER PWR ON, AND GEN 1 OFF). EMERGENCY DECLARED. ON ELECT CONTROL PANEL MANUAL LIGHT STAYS ON WITH SW IN AUTO & EPCU DISPLAYED CURRENT FAULTS, APU FAULTS APU DPCT RELAY/INTFC, BTR 1 TRIP/INTFC, GR1-INTFC, REPLACED EPCU IAW AMM 24-08-1-4 AND PERFORMED RTS ON EPCU. NO DESCREPANCIES NOTED.