I havent tried to convert one from power to manual (or vise-versa), but I can tell you if the rollers/tracks are dry on the regulator neither style will work. My Manual setup wouldn't roll all the way up when I first got it. Not sure of what the problem was I got another regulator from the JY, cleaned it up and added new rollers. Once I got mine apart I found the tracks were dry, but did have some amount of rust scale inside them. The rollers were comletely worn flat on one side (like a sideways D). I pulled the old regulator and practially fell apart on the bench. I wire brushed the tracks to clean out the rust and coated them with a heavy amount of grease. Once I put it all back together the crank can be turned with one finger.
Power gates have the same problem. Water gets in from the top, collects in the tracks and if they are not greased, rust develops. Eventually the rollers stop rolling due to the rough surface and they end up sliding over it. That's when they start wearing. All this friction puts an addtional load on the motor and cable. Sooner or later it can't over come it and something breaks. On a manual it's usually the potmetal crank handle. On power it's the cable/gear or motor itslef.
One trick though, if the motor quits but the regulator looks to be OK and you have to get the window down or up, take the panel off and break out your cordless drill. hook it up to the cable and run it down or up.
