Valcoder on the control panel of the car radio
The roller should be disassembled carefully without using excessive force. The main task is to get to the internal contacts and clean them of dirt and oxides. You can bend the moving contacts slightly so that they make better contact with the fixed contacts when sliding.
It is better to clean contacts using special means. For this you can use, for example, spray cleaner DEGREASER . It is easy to apply to the surface, evaporates quickly without leaving any traces, and cleans well from hardened rosin, oxides, dirt and fine dust. It is better to apply the spray on a toothbrush in a small amount and then carefully clean the surface of the internal contacts of the roller. After this, we assemble the encoder and solder it into the printed circuit board.
Usually, after such cleaning, the encoder operates stably and the problem with chaotic volume control no longer appears.
A dimmer, also called a dimmer, very often fails, especially if it is not installed in the house. The fact is that these devices are very sensitive to voltage changes and can instantly break under increased load. Next, we will look at the main reasons why the dimmer does not work and how to repair faults with your own hands.
So, first of all, let’s talk about what became the “culprit” for the improper operation of the dimmer.
Most often, the dimmer stops working after a light bulb in a chandelier or floor lamp burns out. At the moment of burnout, it may occur, as a result of which one of the most important circuit elements in the dimmer, the triac, burns out. If the triac does not work, the entire circuit fails. 
The second reason why the device may not turn on, or vice versa, may not turn off the light, is that the dimmer works with an energy-saving lamp. We have already talked about the fact that for LED and fluorescent lamps you need to buy special dimmers, specifically designed to work with “housekeepers”. At the same time, it is necessary to choose special ones, not ordinary ones. If you do not take this requirement into account, then the malfunction lies precisely in this reason, which is clearly shown in the video example.
What to do so that the device can adjust the brightness of the light
Another probable cause of the malfunction is incorrectly selected dimmer power, as a result of which it does not work as it should. We have already said more than once that the power of the dimmer should be 30-50% greater than the power of all the light bulbs it regulates. If you missed this point and inserted too powerful light sources into the lamp, it is not surprising why the dimmer does not turn off the light or adjust the brightness of the lamps. We talked about this in a separate article. Well, the last thing that needs to be said is that perhaps the problem is in the electrical wiring on the site: the chandelier-switch.
Now we will do the following - we will look at the main malfunctions of dimmers and immediately provide advice on how to repair it yourself.
If the device does not turn on the light, first check the fuse installed under the decorative cover. During voltage surges, it can burn out, protecting the remaining elements of the circuit from failure. Replacing the fuse is not difficult, especially since leading dimmer manufacturers (Schneider, Legrand) include a spare fuse in the kit, as shown in the photo below. 
When the dimmer does not regulate the brightness of the lighting, does not turn off and does not turn on after the light bulb in the lamp burns out, you need to move on to more serious repairs, because Most likely, the triac does not work - it burned out due to a short circuit. You can try to replace this element of the circuit yourself; for this you need a soldering iron and, accordingly, skills in working with these tools. You may also need a drill with a thin drill bit (we’ll tell you why later). In order to be able to unsolder the broken triac and solder a new one, you need to remove the aluminum radiator from the board, which is rather secured with a rivet. You need to carefully drill out the rivet, then unsolder the triac itself and install exactly the same one, but intact. For all these matters, we recommend using and. 
If you use a dimmer with conventional energy-saving light bulbs, we recommend replacing the bulbs with special ones as soon as possible, because Unsuitable housekeepers should not be used. 
I took these regulators with the KIT of the copter on Ali (in order to play around and try out what a copter is), one burned out before the first flight, and 4 more during the training flights. Now I have time and decided to try to restore it (it’s winter, there’s nothing to do anyway).
I removed the heat shrink, carefully lifted the radiator and saw the following picture:
At the top, marked with arrows, are 5-volt stabilizers 78M05, and I started testing with them.
I checked one and the other respectively. On all five burnt out regulators, the stabilizers turned out to be working. Below the stabilizers are MOSFET transistors, like these:
Two for each phase (calculated by scientific poker):
I was too lazy to figure out how MOSFETs work, so to find burnt ones I resorted to the scientific method described above, took a tester and tried to measure the resistance between the legs. I was lucky right away, on the working mosfets the readings were as follows: the lower ones were about 10 kOhm
Upper mosfets about 70kOhm
Faulty mosfets showed short circuit and 3kOhm
I soldered the mosfets with a soldering iron, but of course it’s better to use a hairdryer. I didn’t have the same ones as a replacement, so I asked a friend, he soldered me these from old motherboards:
They are not 30 amps, but 50, but they fit.
On all my controllers the mosfets flew out in pairs (one phase), on one all three phases flew out.
In total, out of five regulators, four were restored. The functionality was checked using a servo drive tester:
Then I applied thermal paste, installed the radiator and wrapped it in heat shrink:
Well, that's all.
The volume knob no longer turns down the volume. That is, regardless of the direction of rotation, the volume only increased. Disorder...
Let's open the radio and see what's inside. To do this, you need to unscrew the mounting screws and pick out the back cover.
Let's also remove the front cover.
To get to the volume control, it won't hurt us to remove the knob. Usually it comes off easily, but here I had to tinker. Someone put it on sealant. The regulator handle is collapsible, the upper part is supported by curved metal plates. We bend them and remove the top part.
Here we see a very dirty mechanism (by the way, the same problem was with a faulty mouse wheel). We wipe all rubbing parts (contact disc and antennae-shaped contacts) with a cotton swab and alcohol. I also had a “holey round piece” fall off, I had to glue it back on.
We clean the joints of the contact plate and glue it in place.
After cleaning, we make sure that all the rubbing “antennae” are located evenly and at the same level, then we assemble everything in the reverse order. One of the four metal plates that hold the volume control together broke. It’s okay, it will also hold up on three. And if they all break off, then you can put the upper part on the glue, just be careful so that the glue inside does not get on the contact elements. You can go check it out!
If your speed controller burns out, don’t rush to throw it in the trash, it can still be repaired. I will tell you how to repair such devices using the TURNIGY Multistar 20A SBEG4A as an example.
First, let's open the regulator; to do this, you need to carefully cut the heat shrink along the entire length
After that, take the board out of the heat shrink and remove the heatsink 
There are enough details here :) In order to figure out what’s what, here’s a block diagram (schematically)
For clarity, highlighted on the board in color in accordance with the block diagram
After opening the regulator, we begin diagnostics. First, we check by visual inspection for chipped parts, smoke, soot from transistors, short circuits, metal shavings, bad soldering, and crookedly installed parts. If such defects are observed, then eliminate them; perhaps this was the cause of the breakdown, but do not rush to turn it on! There may still be burnt parts. Most often, their control transistors (switches) burn out; I have 6 of them. (Blue color) 3 on each side. They usually burn out from overload or short circuit. There is a lot of information on the Internet on how to check them. But you can quickly check them for the presence of a breakdown between drain and source, drain and gate. If there are any, replace them with the same ones or find analogues according to their parameters. Everything needs to be checked! As a rule, they burn out in pairs on one side and the other. All 6 of them burned out :) Let’s not turn them on yet to celebrate! It is possible that if there was a breakdown between the drain and the gate, other elements burned out.
Next we check SBEG (blue color) It should have a voltage of 5.4 - 5.6 volts. Please note there is not exactly 5 volts! so be careful when you power other devices with SBEG. SBEG is a switching stabilizer. If the voltage is not maintained, then check its components. It consists of a master oscillator (8-leg microcircuit) and a field driver (6-leg microcircuit). You need to check the field filter for breakdown, the protective diode (rectangle to the left of the filter) and electrolyte (yellow rectangle).
SBEG diagram from the datasheet (using the example of LM3485) 
Next we look at the stabilizer for ATmega8a (Orange color) This is a regular 5 volt stabilizer on an LM2931 chip (8 legs). We check the voltage should be between 4.9 - 5.1 volts. If not, replace it.
We look at the datasheet (pinout is also a bonus)
The next step is a 12 volt stabilizer based on 78L12 (pink color). We measure the voltage should be within 11.9 - 12.1 volts. If necessary, I will replace the part.
Scheme according to datasheet
The inventory (gray color) consists of 3 transistors and 3 diodes, which must also be checked for breakdown.
Well, the final stage is the ATmega8a chip (purple). The Chinese decided to save money and instead of ATmega8 they installed ATmega8a, which is several times cheaper. To check it, you need to check the terminals for the presence of a breakdown. In the on state, there must be logical zeros at the pins of the microcircuit going directly through the limiting resistors to the switches. And the outputs going through the inventory must be logical units. If not, perhaps the microcircuit has failed. Also, if you have special equipment, it is useful to check the quartz at 16 MHz (striped rectangle).
We sorted out the diagnostics, I got 6 burnt transistors, which can be treated by replacing them, I replaced them with 30 amps from the motherboard, it looks far from aesthetically pleasing (the transistors are large in size), but it works.
Regarding desoldering, it is not necessary to have a soldering gun, the main thing is more solder and flux. I soldered with a regular 40 watt solder :)
In conclusion, even if it is not possible to adjust the regulator, in any case it can be left as a part for repairing other regulators.
And I would also like to say that my regulator burned out after uploading the kda firmware for multistar. When turned on, it beeped i.e. loaded when gas was supplied, it began to smoke: (Maybe someone can tell me what I did wrong.
Have a nice day everyone!
RaX
