Had to report about fixing my 3107dvs Bosch sander. Ordered a new Ros65vc, so decided to attempt to fix the old sander. Symptoms were hopping, and would not sand at the same speed as was common, so had attempted using it at slower speed, and it got to hopping at slower speeds, so decided it was time. Had been acting up for some time. I googled disassemble 3107dvs, and found a Utube video of a guy taking the housing apart, so watched that, but he did not remove the motor parts. So I went that far, then looked it over and decided I could get the rest apart, as the sander is designed pretty well, in that all the parts are fastened in one half of the housing. So had to unplug 2 wires from the variable speed, remove 2 screws from brush housing, then 2 screws from the lower bearing and the whole thing came out. I unscrewed the fan assembly from the armature, and seemed the bearing in the eccentric offset was rough, so pulled it out of the assembly, found it was dry, put some oil in it, and it spun smoothly. I put a couple drops of oil in the other bearings, cleaned and reassembled the sander, and it works like new again. Just needed a few drops of oil.