hi phillip it is simple really without knowing what symptoms its displaying its a little harder , for example with mine the shaft would stop but i could still hear the elec motor going so i assumed it was one of the toothed rubber belts ,but thought best to check it with the covers off [ remoed all screws and the top cover with the buttons on it the electronics and motor drive will stay in th bottom half ] with the power conected it was clear that the shaft of the elec motor was spinning inside the gear , removed motor then removed gear cleaned shaft and inside of gear and using locktite bearing reataining compound put back together and its been sweet ever since
so yea i guess the long and short of it is pull it down and power it up good luck cheers dan