I have never really been happy with the performance of my x2 mill. The thermal overload has always been too sensitive and the motor is constantly cutting out. Well, last night I was working on my latest gizmo, a rotating/tilting table for my 3" screwless vise, and the mill stopped altogether. I shut the shop down for the night and tackled the problem this morning. (Never attempt repairs while you are pi$$ed off).
The very first thing I noticed when I pulled the control box cover off was a resistor...one of the big rectangular white ones, lying in the bottom of the box. It just fell off!
Typical cold solder joint. I pulled the board and noticed that the OTHER big white resistor was loose as well. Sheesh...COME ON GUYS. Out comes the soldering iron...I tinned the contacts and resoldered both components, then I noticed that the cooling fan in the box was awfully clean. It was clean because it has never worked. I pulled THAT board and guess what. 2 more cold solder joints! Now the fan works, the mill has about 3 times the torque it did before, and if I get heavy handed the motor will stall without tripping the overload.
In the drawing below you can see a proper solder joint has good adhesion to the trace on the board. The component is solidly attached and has good electrical conductivity. A cold-solder joint is usually somewhat rounded in appearance, like a little sphere of solder, that is not well fused to the board. This can happen if the component or trace is not properly cleaned and tinned before soldering, resulting in the solder fusing to only one surface. A nice hot soldering iron applied to the cold solder joint with a little pressure will re-melt the solder and often fuse the connection without having to remove and reinstall the component. This is how I repaired my mill...no additional solder was needed aside from tinning the resistor that had fallen off.
