The sparking around the comunater usually indicates there is a short between the windings of the armature and ground. If nothing else, check between the individual bars and ground. Also there will be a connection to another bar of the comunater. I am curious about the transformer: What purpose did it serve? Was this a set up for 220 volts used in Europe? Or perhaps another voltage set up, as yet unknown?
Have you tried a restarted? If you have not try this: Simultaneously hold down the start button, in the landscape position middle of the right hand side, and the off button, upper left hand edge. Hold for fifteen seconds. The screen will go dark and then a white Apple with a bite out of it will appear on a black screen. It may take a few minutes, then the start screen appears. Sign in and see if all systems are working as they should.
Toe-in is the easiest to explain so I will start there. Toe-in is the amount of difference between the back and the front of the front wheels. If the tires point straight ahead the car would wander and the stearing wheel would not stay in one position. I had a front wheel drive car that the book said needed .5 inch toe-in. I used two blocks of wood the same size, long enough to have about three inches beyond the front and back of the tire. Using the wood to see the out side of the tire, with a tape measure I determined if there was the proper difference between front and back of the tires. By lengthing or shortening the two connecting rods, the adjustment would be brought to the desired measurement. Caster can be best explained by looking at the caster wheel on any roll around device such as a tank vacum. The caster has the major part of the wheel behind the vertical pivot of the wheel. This keeps the wheel going streight. Camber is the same in referance to the vertical pivot, except instead of looking...
Check to see if it is a steel ball or a drop of solder. I do not think a steel ball belongs in the ipod. The drop of solder would not have been left in the unit. Inspection should have caught any foreign material, steel ball or drop of solder. I suspect that a short in the charging system, the only place enough current exists in the unit to melt solder, may have taken out a component. The result may have been a current draw sufficient to destroy enough circuit material to leave the residue you speak of. I think such destruction will be obvious and you will find the culprit. Good luck and as my son says, "keep smiling!"
If the sparks go all the way around the copper strips, also called the commutator, the armature has shorted. That means the insulation between the wires and the iron has broken down in the inside of the armature. Some times it can be as simple as a short between the bars, the copper strips, of the commutator. With the tool unpluged, use an air hose with an air nozzle to blow any trash or dust from the area around the brushes and the communator. If that does not improve the symptoms the next thing is, with the tool unpluged, remove the brushes, often a screw on cap hold them in, and inspect and compare the length. A short length will cause the springs to not put enough pressure on the carbon to make good contact with communtator. In that case, replace the brushes. Also check the freedom of movement of the brushes. If dirt jams the channel the brush slides in, the spring can't push the carbon tight to the commutator. Good luck! This repair will work on other hand-held power tools.
Attach a solder lug to the center screw of the nearest AC power outlet. Just remove the cover screw and put it through a proper size solder lug and tighten the screw back on the cover where you removed it from. Attach the wrist strap when you will be handling ANY electronic parts or equipment.