WOW this is disturbing. I had no idea the newer ones had so much "junk in the trunk." I'm referring to the circuit board. The trouble could be almost anywhere, and of course bypassing the switch---be careful.....is an obvious plan.
I guess if you could figure whether the motor was 120V or not, you could even bypass the whole board.
All three of my Dremels are older non---variable speed. I "solved" that problem by taking a large metal surface mount box, with a front plate which mounts a duplex receptacle on one side, a toggle on the other. Then mount a lamp dimmer in the toggle side, and now you have a box which will control heat on a soldering iron, or speed on your Dremel.
