My Dremel 8200 always works full, without speed control, and perhaps the same fault as yours. If you want I pass photos of the interior ..
+
+
=== Actualización (03/10/19) ===
+
I have looked at it. It is a Mosfet channel n. The model is 80NF03L-04. If you want I pass photos, since I have reviewed my dremel and it is what has burned to me.