I bought two used 6100 and one of them had the buzzer go off, i've soaked it and thought it would run, but then the buzzer went off again. Looking at the post on cleaning I didn't get the bottom piece out of the motor block, so maybe it is stuck in there? Also the orange o ring is stretched too big. I managed to get the outer cover on it but I need a new o ring. Not sure where it is on this site to order it.
http://www.tunze.com/149.html?&L=1&C=US&user_tunzeprod_pi1[predid]=-infoxspare_9999.999
http://www.tunze.com/149.html?&L=1&C=US&user_tunzeprod_pi1[predid]=-infoxspare_9999.999