What was found
PRIM EXT POWER ACCEPT NORMALLY, BUT SEC EXT POWER WON'T ACCEPT. WHENEVER PROVIDE TO SEC EXT POWER, GROUND POWER WILL TRIP BY OVER OR UNDER VOLTAGE. SEC EXT PWR CABLE TERMINALS SHORTED BETWEEN PHASES A & B, LOCATED ON INTERNAL SIDE OF PWR RECEPTACLE. MAY HAVE BEEN FROM FOREIGN MATTER LODGED BETWEEN THE TWO TERMINALS. TERMINAL HARDWARE INSTALLATION ON STUDS OF CONTACT PINS ARE CORRECT & REFLECTS A SECURE CONDITION. SUBSEQ RPLMT OF RECEPTACLE, POWER CABLES, & RELATED HARDWARE RETURNED ACFT TO SERVICE WITH NO RESPECTIVE FAULTS. UPDATE 9/15: METALLURGICAL ANALYSIS FOUND NO FOREIGN MATERIAL AT SHORT CONTACT AREA. ONGOING INSPECTIONS HAVE FOUND LOOSE & WORN CONTACT RECEPTACLE PINS.