What was found
TWO HOURS INTO FLIGHT, EMER POWER ON, LIGHT CAME ON. FOLLOWED QRH & DEPLOYED ADG & SELECTED ADG ELEC. UPON ARRIVAL FOUND LT EMER DC BUS UNPOWERED. CHECKED EPCU & NO FAULT FOUND IAW SSM 24-34-0. RECYCLED LT EMER DC FEED RCCB, B1-1754, CB & BACK TO NORMAL. IAW AMM 24-24-00-4 R & R B1-1754 RCCB AS PRECAUTION IAW AMM 24-24-00-5. PERFORMED EMER POWER SYS TEST PASSED. ADG STOWED & SECURED IAW AMM 24-25-01-4. ACFT OK FOR SERVICE.