usually heat is the culprit,take your non working one and hog out the clear insulation in the back.usually its a bad capacitor.unsolder and take to radio shack or electronic parts place and get another capacitor.usually under a few bucks.solder it back and silicone the back side and problem fixed.do it yourself and save money.bad capacitors usually bloat up or leak so its easy to tell after you remove insulation goop.always have a good ground also..