Dimmer repair

First, you need to figure out what it is and what functions this dimmer performs. A dimmer is also called a dimmer - it is a device that allows you to smoothly regulate the voltage on the load. It is mainly used to adjust the brightness of halogen and incandescent lamps, but it can also be used to adjust the temperature of soldering irons and other devices. The name from English translates as - darken, dim, etc.

Thanks to a dimmer, you can save energy, this happens by reducing the voltage and current passed through the regulator, although the brightness of the lamp will decrease, but sometimes in some rooms this is very useful, and sometimes even necessary, for example, in a room for developing photographs or in brooders for temperature control, etc. The dimmer also helps to extend the service life of incandescent lamps by smoothly increasing the voltage, because the lamps mostly burn out at the moment they are turned on, since before connection the lamp itself and the tungsten filament are cold, accordingly the resistance of the filament is many times lower, and the current strength is higher than when hot . Unfortunately, the dimmer, which had been working for me for three years without problems, suddenly burned out, and I decided to revive it.First, I took it apart. In my case, and generally in inexpensive dimmers, to do this you need to pull out the control knob, unscrew the nut under it, then unscrew the two screws on the back of the dimmer and pull out the board with the parts.

Next you need to visually inspect. Sometimes it happens that an inspection reveals some breakdowns, for example, darkening of resistors, a split or rupture of a triac, a split film capacitor, etc., and sometimes you can see the consequences in the form of a burnt-out track on the board.

In my case, the inspection did not show any defects, and I set about multimeter (tester). Usually the triac in such regulators fails; in fact, this is what happened with my dimmer. There is also such a malfunction: when the dimmer is turned on, the light flashes briefly, this can also be corrected by replacing the triac, and sometimes the dinistor, this happens due to a secondary avalanche breakdown of the PN junction, one of the semiconductors. In the photo, two triacs inside a blue circle.

Checked using multimeter, the triac rang (passed) in all directions, and passed not as a semiconductor, but as a conductor (piece of wire). Having verified that the triac was faulty, I unsoldered it and replaced it with a known working one. Between the triac and the radiator I applied KPT-8 (heat-conducting paste), of course it would have been possible to do without the paste, the paste just fell under (so to speak) hot hands.

My regulator contained a triac with the designation BT 137-600E, it is designed for 600 volts 8 amperes. I replaced it with a BTB 24-600B I had lying around, which, as can be seen from the designation, is designed for 600 volts and 24 amperes, that is, the dimmer became even more powerful. There can be other triacs, but you need to look at the datasheets to make sure they are suitable in terms of power, pinout and control currents.

Next, I cleaned the holes where the triac would be soldered, coated it with soldering flux and soldered it to the prepared place. After that, I wiped the board with a cotton swab moistened with alcohol where there were flux residues.

For me it burned out along with the light bulb, and I assumed that the triac failed due to an arc that occurred when the lamp burned out and provoked a voltage surge.
I also checked the symmetrical dinistor (DB3). It is checked this way, first you need to try using a tester (in diode testing mode) to ring in both directions, it should not ring. Next, screw a 1 Kilo Ohm resistor onto the tester probes, connect the first end of the probe to the dinistor, and between the second end of the dinistor and the tester, connect a 100 microfarad capacitor (charged), the voltage on it is slightly higher than the breakdown voltage of the dinistor. If the tester (in voltmeter mode) shows a falling voltage, this means the dinistor is working. If it is faulty, a replacement can be found in a burnt-out energy-saving lamp. In the photo there is a dinistor in a blue circle.

Just in case, I also checked the remaining parts, although I was sure of their serviceability, since it is mainly the triac that fails and, less often, the dinistor and the variable resistor with the switch. Well, it happens, of course, that a track burns out, this happens due to a short circuit in the circuit section of the light bulb and the regulator or incorrect wiring in the junction box, but it burns out when the triac fails. By the way, some dimmers do not work correctly if the phase with zero is not connected correctly, but even if they are mixed up, nothing bad will happen.

In the photographs below, you can see the minimum and maximum filaments of the light bulb after repair.


And the actual video of the dimmer in action.My advice to those who decide to repair a non-working regulator themselves. I do not recommend neglecting safety precautions and performing all manipulations with the dimmer only when the power is disconnected from the network. When measuring under load, be careful, since the entire circuit is not galvanically isolated. When choosing a triac, buy one that is at least 30% more powerful than the connected load, and preferably 50% or more (in some cases you will have to change the circuit). Don’t be lazy to check the other details, because there aren’t that many of them, in my circuit there are only 7 along with the triac. It has happened to me personally that they brought dimmers that had faulty switches themselves, built into a potentiometer, triac, or dinistor, but in principle other parts may also refuse to work.
I hope my information will help someone when repairing a dimmer.