As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU GENERATOR WILL NOT ACCEPT POWER. APU GENERATOR STAYS ON ABOUT 3 SECONDS, THEN TRIPS. VERIFIED HMG OPERATES NORMALLY PER AMM. BPCU BITE SHOWS GENERATOR DIODE IS OPEN AND CHANGING GCU, NO HELP. RPELACED APU GENERATOR. OPERATION CHECKED NORMAL.