Seeing as big companies make them, appliances can often seem as much more complicated as devices than they really are. This is as true of blenders as any other appliance, and fixing a busted blender is surprisingly an easier task than you would expect.
There is three typical causes for blender malfunction: motors that become burnt-out, blades that get clogged, or an interruption has occurred in your electrical connection. The first two causes are easy to diagnose and fix, but in the case of diagnosing an electrical interruption, you will need a voltmeter and a contact sprat solvent, which are handy tools to have in your home regardless.
To test the blender's electrical, disconnect the electrical cord and turn the blender switch on. Set the voltmeter on the RX1 scale and carefully place the meter's two probes onto the two metal prongs of the plug. While watching the meter's readings, test out each of the blender's switches, one at a time and note the markings.
Low readings indicate a normal switch that is functioning perfectly. What you want to look out for is an infinity reading on the meter, which is indicative of an electrical defect. To investigate further, you will need to expose the screws that hold the switch housing cover in place. While the device is still unplugged, remove the plastic faceplate that covers the housing and, subsequently, the screws that attach the plate to the housing.
Now that the mechanism is exposed, use the contact spray solvent to clean the contacts, openings and terminals at the rear of the switch block. After you have cleaned out the mechanism, plug it back in and test the switches again. This usually fixes the mechanism, but if the blender continues to not work, unplug it again and find the fuse, which is usually located at the end of a wire lead coming from a terminal connected to the power cord.
With your voltmeter still set to RX1, clip the probes ends to the two lead wires or terminals. If the reading is high again, disconnect the probes and look on the metal cap of the fuse to find the size and write it down, as it will need to be replaced. This will almost certainly fix a purely electrical issue but if the issue is with the blades, that’s another story. While the machine is still unplugged, carefully try turning the blade shaft. Debris will usually be very easy to see and easy enough to dispose of but in rare cases, you may have to replace the coupling.
If none of this works, you more than likely have a burnt-out motor, which will require you replacement, but considering the cost, you will likely just want to buy a new blender for your home. Otherwise, replace all screws and plates, and get some ice, tequila and margarita mix, and whip yourself up a congratulatory drink.