As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SHORTLY AFTER TAKEOFF LIGHT IN APU FIRE HANDLE FLICKERED FOR SEVERAL MINUTES, FOLLOWED BY A STEADY LIGHT. NO OTHER FIRE INDICATIONS WERE NOTED. APU FIRE HANDLE PULLED, BOTTLE BLOWN. REMOVED AND REPLACED OPERATING POWER UNIT FOR APU FIRE DETECTION IAW B727-200 MM CH 26-15-003-4. FIRE TEST NOW CHECKS NORMAL.