As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LT BUS POWER INTERUPTIONS AT 33000 FT. RAN AC POWER INTER- CHECKLIST. APU WAS STARTED AND EMERGENCY DECLARED AND A DESCENT INTO PHL. PHL MTC FOUND LEFT ENGINE FREQS AT 383 ON ENGINE RUN. WOULD NOT HOLD BUS WHEN LOADED DOWN. REPLACED BUSS POWER CONTROL UNIT.