When you open up the converter, it has a bunch of canned power capacitors, correct? If so, my GUESS is that you have some bad capacitors. Look for the ones that are swelled or really hot.
Did you have some recent power outages or local lightning strikes? Those caps are AC rated electrolytics. Make sure if they need to be replaced, that you pay attention to the voltage ratings. If I remember right, they were typically rated for 600 VAC.