TC reported smoke external alarm on front DT. Staff(WDL) checked and feedback no abnormality.T411 line clear and feedback - no abnormality.. SM ADM check ed on external of FDT, all ok. ~~~~~ #3667 Found external smoke detector PCB faulty. Replaced faulty smoke detector unit. Carried out function test ok.    Done by Saini/Din/Koh  22/10/20.