As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CLIMBING THROUGH 10,000 FT, RECEIVED "BUS AC GS OFF" WARNING. DECLARED EMERGENCY AND RETURNED TO DEPARTURE. CREW REPORT INDICATED THE EMERGENCY POWER ON LIGHT WAS ILLUMINATED. PERFORMED FUNCTIONAL CHECKS WITH NO FAULTS FOUND. REPLACED APCDU, EMERGENCY DC POWER RELAYS, LT & RT PCDU'S. REPLACED LT & RT & EXT POWER RELAYS WITH ALL CHECKS NORMAL. PERFORMED FUNCTIONAL CHECK FLIGHT WITH NO ISSUES NOTED.