As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APPROX 4 TO 5 MIN AFTER T/O, NR 4 MAIN CARGO SMOKE ALARM SOUNDED AND ILLUMINATED. LIGHT REMAINED ILLUMINATED FOR A FEW MIN AND THEN WENT OUT. NO SECONDARY IND OF FIRE OR SMOKE. REMOVED AND REPLACED NR 4 SMOKE DETECTOR, OPERATIONAL CHECKS NORMAL PER B727 MAINTENANCE MANUAL CHAPTER 26.