1555 smoke internal, now BSH NB. ~~~~~ 1555 smoke internal, now BSH NB.  1555 smoke internal -FC 731(Fire internal & external) -FC 735(Fire & smoke detector lost power) Clean smoke detector.No water ingress. Swop SDR1 relay from 1555 TO 2555. Replaced DC DC converter power unit. Function checked - OK. (DC DC Power supply unit S/N) (OLD S/N:A101484) (NEW S/N:A103769) OPS20 Raised to check  smoke detector. Sarma/Anand 45240 BSD: 1555 to check smoke detector