As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WITH LEFT GEN RUNNING RT AC BUS OFF MSG. REPLACED BPCU SINCE FAULTED, NO HELP. T/S PER FIM REMOVED AND REPLACED APU BTB, NO HELP. FURTHER T/S SHOWED THE STBY PWR PANEL INTERMITTENT. REMOVED AND REPLACED STBY PWR PNL. RAN LT ENGINE, CHECKS OK. ETOPS CATEGORY 'E': PROBLEMS WITH SYSTEMS CRITICAL TO ETOPS.