As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON PREFLIGHT, AFTER TURNING ON APU BLEED AIR, LOUD WHINING SOUND CAME FROM THE REAR OF ACFT ACCOMPANIED BY BURNING ODOR. SHUTDOWN APU BLEED AND RAN BOTH ENGINES WITH SAME RESULT. ACM TURBINE IS SEIZED. R & R THE ACM IAW MM 21-51-00. OPS AND LEAK CHECKED GOOD.