First you need to figure out what it is and what functions this dimmer performs. Dimmer is also called dimmer - a device that allows you to smoothly adjust the voltage on the load. It is mainly used to adjust the brightness on halogen lamps and incandescent lamps, but it can also be used to adjust the temperature of a soldering iron and other devices. The name from English translates as - dim, dim, etc.
Thanks to the dimmer, you can save electricity, this happens by reducing the voltage and current through the regulator, though the brightness it will decrease, but sometimes in some rooms it is very useful, and sometimes even necessary, for example, in a room for developing photos or in brooders for temperature control, etc. And the dimmer helps to extend the life of incandescent lamps, smoothly raising the voltage,because the lamps mostly burn out at the moment of switching on, since before the connection the lamp itself and the tungsten filament are cold, respectively, the resistance of the filament is many times lower, and the current is higher than with a hot one. Unfortunately, the dimmer that worked for three years without any problems, suddenly burned out, and I decided to reanimate it. For a start, I took it apart. In my case, and mostly in not expensive dimmers, for this you need to pull out the knob of the regulator, unscrew the nut that is under it, then unscrew the two screws at the back of the dimmer and pull out the board with the details.
Next, you need to visually inspect. Sometimes it happens that the inspection reveals some damage, for example, darkening of the resistors, splitting or breaking of the triac, splitting of the film capacitor, etc., and sometimes you can see the consequences in the form of a burnt track on the board.
In my case, the inspection did not show any defects, and I took up the multimeter (tester). Usually in such regulators a triac fails, and this is exactly what happened with my dimmer switch.There is still such a malfunction, when the dimmer is switched on the light flashes briefly, it can also be corrected by replacing the triac, and sometimes the dynistor, this happens due to the secondary avalanche breakdown of the PN junction, one of the semiconductors. In the photo, two triacs inside the blue circle.
Checked with a multimeter, the triac rang (skipped) in all directions, and skipped not as a semiconductor, but as a conductor (piece of wire). Having made sure of the failure of the triac, it was repaired and replaced by a worker. I put KPT-8 (heat conductive paste) between the triac and the radiator, you could certainly do without paste, just paste came under (so to speak) hot hands.
In my regulator stood a triac with the designation BT 137-600E, it is rated at 600 volts 8 amperes. I replaced it with the BTB 24-600B, which I had overlooked, as you can see from the designation, it is designed for 600 volts and 24 amps, that is, the dimmer has become even more powerful. Triacs can also be other, but you have to look at the datasheets to match the power,control and control currents.
Then I cleaned the holes where the triac will be sealed, get rid of the soldering flux and solder it to the prepared place. After that, rubbed the board with a cotton swab moistened with alcohol where the flux residues were.
I burned it along with a light bulb, and I assumed that the triac had failed from beyond the arc, which appeared when a lamp burned out and provoked a power surge. I also checked the symmetrical dynistor (DB3). It is checked so, first you need to try a ring tester (in diode test mode) in both directions, it should not ring. Next, connect a 1 Kilo Ohm resistor to the test leads of the tester, connect the first end of the probe to the dynistor, and between the second end of the dynistor and the tester, connect the microfarad capacitor 100 (charged), the voltage on it is slightly higher than the dynistor breakdown voltage. If the tester (in the voltmeter mode) shows a falling voltage, this means the dynistor is working. If it is not working, a replacement can be found in a burnt-out energy-saving lamp.The photo is a dynistor in a blue circle.
Just in case, I checked the rest of the details, although I was sure they were working, as mainly the triac and less often the dynistor and the variable resistor with switch. Well, it happens, of course, that the track burns out, this happens because of a short circuit in the circuit section of the light bulb and the regulator or the wrong wiring in the junction box, but it burns out already when the triac fails. By the way, some dimmers do not work correctly if the phase with zero is not properly connected, but even if they mixed up nothing bad will happen.
In the photos below, you can see the minimum and maximum heat of the light bulb after repair.
And the actual video of the work of the dimmer. My advice to those who decide to repair not working regulator independently. I do not recommend to neglect the safety technique and perform all manipulations with the dimmer only when the power is disconnected from the network.When measuring under load, be careful, as the whole circuit is not electrically isolated. When choosing a triac, buy it at least 30% more powerful than the connected load, or better by 50% or more (in some cases you will have to change the circuit). Do not be lazy to check the rest of the details, because there are not so many of them there, in my scheme only 7 together with the triac. I personally happened to bring dimmers, which had failed switches themselves, built-in potentiometer, triac, or dynistor, but in principle can refuse to work and other parts. I hope someone with dimmer repairs, my information will help.