Some problems are easy to solve. If you have a broken locomotive or power supply, or if your model trains are no longer made, you may want to find a professional to make the repairs. For many current sets, it is cheaper to replace than repair. If you do notice heavy dirt or corrosion, it can usually be removed with some special abrasive cleaning blocks and liquid cleaners available at hobby stores. A strong eraser and rubbing alcohol will also work. Do not use steel wool. The steel shavings can be drawn into your engine’s motor.  If you don’t detect any current at the supply outputs, disconnect the wires to the track and test again. If you get a light, then you probably have a short in the track or wires. If not, then the problem may be a faulty power supply. Contact the manufacturer or a local hobby shop for a qualified service or replacement. If you are getting good results with this test, the problem is probably in the locomotive itself. If you are just starting out, your best option is to return the locomotive or find a local service location. If you don’t get a good light or a second locomotive won’t work, then the problem is probably on the track or the wires. If you are using the 2-rail track, make sure you haven’t created a short in a reversing loop or wye. Switches and crossings can also cause a short if the opposite rails touch without an insulated break. If you’ve just changed or added track, start searching there. Remove the suspicious piece and see if the short goes away. Continue disassembly until you find the problem. If you are building a large layout, it is a good idea to test as you go.