Does your bike have an eccentric for the timing chain tension? If so does it work good?

I had trouble with my timing chain falling off and ended up with a big derailleur gear to replace it(took the little tension gear off and put a big one on, just to get the thing tight). This is my beater tandem; my other tandem has an eccentric and what a difference. Don't think i would go back to a timing chain external tensioning device. Makes the bike sound like blank.....