Yep, had the same problem myself. Below is what I had posted last year, should solve your problem. I had called Delta and they sent me a new pully, but I did this fix in the meantime and it's still good.
For those of you with one of these who may have a problem with the bushing separating from the upper rear belt pulley, I found it's easy enough to fix. First move speed indicator to fastest speed, this loossens(relaxes) belt, then it's not too difficult to release the spring. After you get the upper pulley off, drill and tap a 10-32 hole and install a set screw to hold bushing in place. To re install spring I just compressed it in a vise and tied it with plastic tie straps to hold it while I got the keeper ring back on, then cut the tie straps and pulled em out. Hope this helps someone.