TC reported TIMS showed smoke exterior at Rear DT. Staff (YCK) checked and feedback no abnormalities . ~~~~~ TC reported TIMS showed smoke exterior at 3677. Staff (YCK) checked and feedback no abnormalities. CE 3677 checked & found having smoke external pre-alarm fault. Check no abnormality, reset fault cleared.  3677 Check and found smoke external detector PCB Rusty and water seepage. Change out and function test ok S/N:N.A Notification:2617598 Done by Sanip/Koh/Jack 45488