What was found
AFTER TAKEOFF GOT MID 1 AND MID 2 MAIN CARGO SMOKE WARNING. RETURNED TO DEPARTURE. DETECTOR 7WU, MID 2 DETECTOR 11WU, MID 1 DETECTOR CONTROL UNIT AND MID 2 DETECTOR CONTROL UNIT IAW TSM 26-19-00 AND REF 26-19-12-04. R & R 4WU, 8WU AND 12WU MAIN DECK SMOKE DETC REF M/M26-19-12 ALSO REPLACED THE FILTERS IN SAME LOCATION MM REF 26-19-13. AFTER REMOVAL AND INSTALLATION OF ALL COMPONENTS, PERFORMED REQUIRED TESTS IAW MM REF 26-19-34-04 AND 26-19-12-04. ALL TESTS PASSED SATISFACTORILY. ADDITIONALLY, PERFORMED WC 32X0302 MAIN DECK SMOKE DETECTOR OPS CHECK WITH NO FAILURES. ACFT OK, RETURN TO SERVICE.