It was my grandpa's, and although I can't find a direct reference to it anywhere on the net, I'm guessing it's anywhere from 40 to 60 years old. It worked for some time, but sadly, it recently has stopped. When I was soldering the other day, I noticed the wand getting progressively colder, until it eventually wouldn't even melt solder. Now, it turns on (or at least the indicator light does), but the iron does not heat up. Is this fixable or do I need a new iron?