As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW CALLED IN, IAW QUICK REACTION HANDBOOK, DIVERTED DUE TO A RIGHT AC BUSS FAILURE EICAS MESSAGE INDICATION, APU FAILED IN FLIGHT TO START. EMERGENCY DECLARED. LANDED WITH NO FURTHER ISSUES NOTED. THE AIRCRAFT WAS GROUNDED. TROUBLESHOT TO FAULTY RIGHT ENGINE IDG WHICH WILL NOT MAINTAIN CORRECT DC/AC POWER. REMOVED AND REPLACED THE RT BUSS POWER UNIT, AND IDG . OPS CHECKED SATISFACTORY. ACFT RELEASED TO SERVICE.