Thanks for the responces and yes I have tried F8. I will try to reset the CVs, thanks again.

 I have an S4 with sound locomotive that I bought about a year ago. I have not ran it a lot but I put it on the track today and the sound would not work. The lights etc work fine but there is no sound coming from the unit. I have two other "bachmann DCC sound on board" units including another S4 and their sound is working fine. I am stumped as to why this units sound has stopped working, any suggestions?