I have a yamaha yas-23 alto. Two of the four lugs holding the lower key guard have come unstuck. (What is the build quality of these like? Is this commmon?). Anyway I'm keen to reattach them. I understand that these are soldered to the body of the horn. Is it possible to do with an electric soldering iron? Or do I need to use a propane torch (or similar)? I have both - but am concerned about burning the lacquer (or generally making a mess of it). All advice welcome.