It is very easy to fix power tools these days, thanks to online manuals, and the availability of power tool spare parts online. Power tools generally only in certain ways. Usually it is due to broken brushes, switches, drive belts and power cords. All of these are easy to get hold of and replace.
Any power tool that uses a drive belt usually dies because it has broken. It is easy to tell if a drive belt has broken as the motor will spin, but nothing will happen. Doing an online search containing your power tool model and replacement drive belt should provide you will the part number. Once you have that you can do a search with that part number and find a good price from a good seller, it is then very simple to replace the belt with help from an online manual.
Brushes usually don’t die suddenly and are really easy to check on a good power tool, so they can be replaced before they die out. They are typically situated under a plastic cover held in place with a bolt. Brushes for a specific power tool can easily be replaced and brushes are easy to find on the internet by discovering the model’s part number.
Power tools that have a powerful motor tend to suffer from a broken switch. Circle-saws almost always stop working due to a broken switch, body grinders are also likely to have a broken switch if one dies. Again, an internet search will reveal the part number of the switch, it is then a case of replacing it. This is easily done by removing the wires to the switch, pushing out the old one before pushing in a new one and reconnecting the wires. Simple!
Broken power cords are more difficult to diagnose, but are incredibly easy to repair. a pair of meter clips attached to needles that have been pushed inside the power cord (with the power off) should reveal where the break is in the internal wires. Then the cord can be cut and another cord can be attached. Power cables are very cheap and can easily be found at retailers selling power tool spare parts. It is also possible to use an old power cord for an electronic device that is no longer used.