The 712 ran from 1984-1989 and is TOL.
Main areas to check are worn/stiff/squeaky drum rollers, stiff belt idler wheel from lack of lubrication, worn belt, worn front drum glides, excessive play or stripped blower wheel, broken or missing lens for the drum light (check the light bulb too), lint buildup, especially around the motor. Check the condition of all of the seals: Front/Rear drum seals and blower housing seal.