What was found
CREW REPORTED ONCE AT CRUISE, NOTICED CB APU BAT BUS-APU BAT CONT POPPED. AFTER CB POPPED EICAS DISPLAYED SEVERAL ADVISORY AND STATUS MSGS REF ALL THREE IRU'S AND APU HOT BATTERY BUS NOT POWERED. RESET CB AND SOME MSGS CLEARED BUT THE ADVISORY AND STATUS MSGS REF ALL (3) IRU'S DC FAULT REMAINED. CREW DUMPED APPROX 100K OF FUEL AND ELECTED TO RETURN TO THE FIELD. FOUND CMC MSG 24720, T-S PER FIM24-60 TASK806. REPLACED CB C10340 PER MM24-60-01 TEST PASSES REPLACED APU BATTERY PER MM24-31-06 AND APU BATTERY CHARGER PER MM 24-31-07. BOTH OPS TEST NORMAL. 6493CB P6-J9 APU BATTERY BUS AND APU CONTROL RESET, NO FAULT MSG'S.