Many power tools that no longer work or work intermittently can often be repaired fairly easily. Generally one of three problems is occurring, the tool is full of dust, it has worn out brushes or a defective power supply. These are all repairs that anyone with a basic mechanical aptitude should be able to undertake.
Before dismantling the tool have a small container to hold the screws and parts that you remove, study an exploded drawing of the parts to familiarize yourself with their layout and function. If you don't have a drawing one may be found here:http://doit101.com/Repairs/powertoolrepair.html Replacement Tool Parts Make drawings and notes on paper and take digital pictures of anything that seems complicated to refer back to when you are assembling the tool, if you have to order parts it may take days or weeks to get them so it may be hard to recall all the details in the future. Make sure the tool is unplugged before taking it apart, if you have been troubleshooting it is easy to forget to pull the plug. Always restore a tool to its original condition, never disconnect or over-ride a safety feature that the manufacturer has built into the tool, these are there for a good reason, your safety! Dust If a tool runs hot to the touch when you are using it in normal conditions it is probably telling you it needs help. Air is drawn in through intake ports by the fan on the motor and expelled through output ports thereby cooling the tool. Sawdust, a by-product of woodworking, will clog these ports as well as lodge into other greasy nooks and crannies of the tool restricting air flow, eventually the motor may overheat to the point that it will melt down and die. If you have an air compressor give the intake port a shot of air with the tool running when you are finished using the tool for the day. Lacking an air compressor the tool should be disassembled when a noticeable amount of dust has accumulated in the air ports and the dust removed with a brush. Be careful not to damage the fan blades when doing this. Brushes If the tool needs help to get going or there is excessive sparking in the motor, (up to 1/4" long arcs are normal) the brushes probably need to be replaced. External Cover Internal Some tools have external covers that can be removed to change the brushes, others have to be partially taken apart. Be careful when removing the covers, the brushes are spring loaded and may pop out on you. Examine the length of both brushes, if they are less than 1/4" long they will need to be replaced. Brushes may be ordered as original parts from the manufacturer or generic products are available, either will work just fine. Some new brushes are flat on the end and need to be seated to the curvature of the armature by running the tool with no load for a while. Power Supply Things to check in the power supply are the power outlet, the cord and the switch. Check the outlet first, make sure that the circuit breaker has not been tripped. Physically examine the cord for cuts or frayed sections, if the cord looks good wiggle it where it enters the tool and at the plug, wires will often break from stress at these points. A new generic plug can be put on the cord, if the cord has to be replaced the tool will have to be disassembled, cut the wires off about an inch long with some of the coloured insulation remaining on the stubs. Fit the new cord and attach the wires one at a time by removing the old stubs and attaching the new ones by matching the colours. Switch and Power Cord, Skillsaw Model 5250 If the switch is defective you will have to order a replacement part, you will need the model of the tool for this. When you get the new switch compare it to the original, draw a diagram of the wiring on paper, then replace the switch by removing and connecting one wire at a time if possible. Ordering Parts Parts for most brands of power tools may be ordered online here, you will also find a schematic drawing of the tool: Repair parts for Accuset tools Repair parts for Black and Decker tools Repair parts for Bosch tools Repair parts for Delta tools Repair parts for DeWALT tools Repair parts for Hitachi power tools Repair parts for Makita tools Repair parts for Milwaukee tools Repair parts for Panasonic tools Repair parts for Paslode tools Repair parts for Porter Cable tools Repair parts for Senco tools Repair parts for Skil tools Tool Repair Parts for most major brands of power tools
