oh… and for a testing methodology… if you are replacing things like power resistors or places where a lot of current should flow, you can use a current limited supply or a smallish buck/boost convertor just in front of your arduino/ramps. They will undervolt and turn off before you burn things out. I’ll do a basic calculation of the current that is expected to flow in the device when heating up (V=IR, V/R=I) and them make sure that my buck/boost or current limited supply can produce about that much, but not very much more before it shuts down.
alternately, you can also plug the things in with your fingers on either the power mosfet or the regulator and see if it gets really hot right away and immediately unplug it.
Both options will help you save the devices before you let the smoke out.