Well little update.. Thanks to all, decided to test bell from control panel,, forced bell test and the disabled,, bell continued to sound. Ear defenders ready unscrewed cover from bell, and pushed screw anti tamper fully back ,, bell stopped. seem anti tamper as you said was the culprit. cleaned out token spiders replaced cover while bell sounding ensuring screw was uber tight, bell stopped .. tested force bell at panel on and off,, all working fine.. Cherrs for guidance , much appreciated.