I have a Hakko, 935 I believe ( it's packed away in my RC stuff at the moment ).
I purchased it, I'd hafta say at least two years ago. It was an Ebay deal, and came with tips that ( I'm betting ) were not Hakko tips. However, up until very recently, it has been flawless. Basically, the solder ( Kester 63/37 ) just balls up, sputters a bit if I move too much flow too quickly, and simply falls off the tips. Just yesterday, I even purchased a genuine Hakko bagged tip from my LHS...same thing. I can tell it does in fact still transfer heat through the wiring, and I can effectively "force" it to break a connection by adding solder as it will melt once it is on the wire...just not on the tip. I've also tried playing with moving the heat control knob, thinking maybe it possibly was out of calibration somehow and too hot. No change. As I'm typing this, the one thing just came to my mind that I have yet to try is different solder. The roll I have is probably no older than a yr. Is it possible that the solder has been contaminated somehow or simply gone bad? Any clues, hints, advice aside from testing another roll which I'll do tomorrow? Is the iron done, time for a new one?

Thank You for your time and thoughts.