This video outlines the basics of power tool and appliance electrical diagnosis. You can use a multimeter to test tool and appliance cords and switches, the two parts usually responsible for electri...
Usually grinding noise means the gears on worn. You will have to disassemble the the unit and inspect the Output Shaft Assembly. If the teeth on the gear are worn, you will probably need the complete Motor Assembly as the pinion gear may also be worn. If they are okay, check the bearings. This could be an expensive repair. But since it is no longer made and depending on how much you use it and like it, it might be worth the cost.
Here are schematics on both the saws in question.Ryobi P550 and, Ryobi MS181. Look at both of them and compare it to the saw you have. There are differences in both saws so you should be able to tell.
Hope this helps,
light weightgood power but table hard to turn when dirty from uses pain to clean.wood gets traped under tableim a contrator all in all its good tool great for stops on replacement window (this and cordless finish gun) make s working on 3rd floor quicker