My Dremel was either intermittent or died when under any load. An air blow out/clean made no difference. Brushes were basically new. I disassembled the unit and noticed a tiny piece of metal fell out. This turned out to be part of one of four slide contacts between the circuit board/switch assembly and the external main coil assembly. These 2 main parts connect together via 4 pins and 4 sliders. Two had broken so the contacts were loose at best but mostly non-existent. I was able to give it a McGyver fix with thin slithers of metal that help to maintain the contact. How did this happen? I do not know. My Dremel is out of warranty but has not had that much use. Well ,fixed and useful for now. Hope that description helps someone else fix their Dremel.