TIMS showed Smoke External Alarm at car1526. Staff(BGB) checked and confirmed no signs of fire on e xterior or interior of train. Rear T417 line clear and confi rmed no abnormalities. ~~~~~ TIMS showed Smoke External Alarm at car     FC-723 both M1 car,further check  found smoke detector pcb having rusty,but no water imgress,c/o as preventive measure. #1526-smoke detector Not: 2482394 #1525-smoke detector Not: 2482393 Done by Sanip/Koh/Firdaus.  23/04/23 as pre