As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE CREW REPORTED THAT DURING APU START, IT FAILED TO START. TROUBLESHOOTING DETERMINED THAT THE STARTER & GEN DRIVE ADAPTER WAS BROKEN. THE DRIVE ADAPTER WAS REPLACED WITH NEW, PN 3861055-1. OPERATIONS CHECKED OK. APU 1561.5 TT 2032 TC.