As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING MAINTENANCE, FOUND MODEL PS823 EMERGENCY POWER SUPPLY INCORRECTLY REPLACED WITH PS835 EMERGENCY POWER SUPPLY. THOUGH SIMILAR, THESE UNITS ARE NOT DIRECT REPLACEMENTS FOR ONE ANOTHER. WIRING CHANGES ARE REQUIRED PER JET/BF GOODRICH SERVICE DATA. AIRCRAFT ALTERED PER APPROVED DATA. (X)