As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU ELECTRICAL INOP. AIRCRAFT LOG INDICATED THAT THE APU GENERATOR HAD A BPCU GENERATOR TRIP MESSAGE DUE TO A DIODE FAILURE. THE APU GENERATOR WAS REMOVED AND REPLACED, OPS CHECK OK. SHOP FINDINGS INDICATED THAT THE UNIT HAS BEEN OPERATING FOR TEN YEAR AND HAVE FAILED DUE TO NORMAL WEAR AND DIODE FAILURE.