The design of the mini-lathe motor controllers is not robust. They will continue to fail. What I would recommend is to fix it once, and make your first project a housing and jackshaft for adapting an industry standard induction motor, either single or three phase, to drive the lathe. These arrangements have lasted for decades or more on lathes all over the world. Pay no attention to the fact that I have two lathes with bad drives on them. One of them has a misplaced countershaft and cracked insulation. A quick rewire and rearrangement and it is now working. The second has a bad starting capacitor. One tug starts it going; just don't let it hum for too long. Once I get to the electronics store, it will be self starting for a few bucks. Should be good for another 20 or more years.