Don't Replace Parts Randomly; First Learn to Measure the Components that Fail Most Frequently.

Hello everyone. This is Professor Nelson from Electronics. Today we're going to talk about the components that most frequently fail on electronic boards. This is so you don't have to check every single electronic component to repair any board. For this purpose, we brought these two boards and today I'm going to show you which components tend to fail most often. So, without further ado, let's watch the video. All right, the first thing we're going to do is check the components near the power outlet. Components like these two here. Here we have a fuse. Similar to this one here. Fuses usually blow when too much current passes through them. Thus protecting our boards. Therefore, we only need to check if there is continuity between its pins. That is, between this point and this point, we need to check for continuity. This is usually the most common failure. However, next to it we have another component. This one here. This is a varistor. A varistor is a component that works like a very high value resistor. Like this resistor, which under normal conditions has a very high value. That is to say, it doesn't work. However, if the voltage at the power outlet experiences disturbances, that is, if very high voltage spikes appear, it is in these situations that the varistor begins to work. Its resistance value reaches a value close to zero. Because of this, it will work as if it were a short circuit. This short circuit caused by the varistor will cause the fuse to blow, thus protecting our circuit board. It can work several times in this way. However, at some point, the varistor will burn out. That is to say, it will explode like this varistor. A varistor normally has to have a fairly high resistance value. Therefore, we set our multimeter to kiloohm resistance. We check the varistor.