ok

I know that when that sound occurs while running, it means the rectifier and speed control just went to the Big Workshop in the Sky... probably because the armature is bad. I repaired my speed ctl several times, but it was never quite the same. I miss it...

You can order this part from Dremel Service Center at 1-800-437-3635.

My problem is the same as above: the coupler is broken and I need replacement for this coupler. Do you have this replacement part?
Thank you

As posted from another user... You can replace this with standard vinyl tubing id 1/4 od 3/8. Just slip one end over drive gear and measure where to cut the the other end (about a 1/8 of an inch from the tool shaft gear.) It's about 7/8 inches long. Press each end of the tubing over each gear, reassemble and fixed. I bought some today (12/29/2010) 1 foot for 26 cents (that's enough for 12 repairs). It works perfectly!!!

I just repaired my broken coupler with tubing suggested by John in response #3. It works just fine. Thanks John for a great suggestion.

I would start with the common culprits. The cord, switch, and brushes. Unfortunately there are not many parts still available for your Dremel.

Good luck!

-Mark