Yeah, I've had a 936 for a long time and until recently, I was very happy with it. Then I noticed that I was having to really crank it up to get the solder to flow of things like terminal strips. I kinda figured that "heck,.. I've had this thing for a decade and abused it mercilessly. Maybe I need to step up to the bar and get a new one?"
Being the cheap skate I am, I decided to take it apart and just replace what was bad. While I was disassembling it, I noticed that the tip was a little off center. I have to admit that I wasn't too awful surprised since I've used the thing to do everything but pry nails out of boards. Also, the thin sleeve that contacts the heating element was no longer attached to the inside of the tip.
Then I ended up having to use a hammer to get the tip out! When I did, I could see that the outside end of the tip and the inside was not only badly bent, but the point where the two met was cracked halfway around!
I must've stepped on it one day without noticing or something!
Well, to end this story, I ran over to Fry's and picked up a couple of replacement tips, put one in and wow! God knows how long I'd been limping along at about half the watts! (if that)
So now, my 936 is better than ever. It's a freakin' dream to use again.
Great tool! Believe me, if it can survive a decade with the likes of me, it's almost a god damn miracle!