The volume control does not work. Two more dimmers. Appearance of printed circuit boards

When overloaded (drilling a large number of holes in concrete, for example), the FIT electric drill often breaks down the speed controller combined with the power button. To repair it, you must first carefully disassemble the drill, remove the regulator from it and disconnect the wires from it, having previously written down which wire is connected to which contact.

The regulator body is disassembled by bending the sides and removing the cover from the clamps, without glue. We must be careful and leisurely - there are 2 springs there that miss the light and flying))).

With the mechanics, everything is not difficult - we clean the contacts and rinse them with alcohol to remove dirt. The board with the circuit can be easily removed by first sliding the copper squares of the clamp-contacts out of the grooves. The only element of the circuit that fails is the triac. We find it and “neutralize” it by removing the conductors suitable for it (we bury it on the spot).

We make a tap from the control electrode with a thin stranded wire (to fit under the cover) and lead it into the existing hole during assembly. Reassembling the regulator is not a problem (if you are careful and deliberate!). From the regulator terminals (not from the phase terminal) we make 2 additional ones. outlet with a flexible wire for connecting a triac. It becomes a remote element of the regulator. (there is enough space in the handle for its location).

At the beginning of March, we managed to purchase an excellent toy radio-controlled jeep, which has a powerful 380-series motor and a servo with smooth rotation control, after which this device was raced in snow, rain, dust and sand. Moreover, tests of the car on more than 30 races showed the following: he doesn’t care at all! I was already flooded with water up to my ears, covered in sand, covered in wet snow from head to toe, and was flying head over heels on the asphalt from a springboard - but I drove stubbornly (except for the wires that came off a couple of times on the connector of my homemade 2S battery).

But then the old woman found something rotten - the speed regulator on the common control unit burned out. And it was like this: this jeep has a super-speed mode, which can only be activated by turning the key in the remote control. This is such protection from children, because then a 2-kilogram car turns into a heavy projectile that can destroy a child in a collision.

Sometimes I turned on this super speed on the asphalt, but then I decided to run it on the grass that made it difficult to move. And of course, the motor control mosfets in the bridge overheated in the second minute of the race. The car stopped driving forward (and it only drove backward immediately at maximum speed).

At first, for some reason, I thought about the remote control - suddenly there was a button where it got stuck or the contact in the switch disappeared. Naive thoughts! The remote control worked without problems (this is determined indirectly by the change in its current consumption during different presses).

We assemble the remote control and move on to the difficult part - disassembling the servo and motor control unit, called FY-RX01.

RC regulator circuit

This is a block containing inside a 2.4 GHz radio receiver, servo control and a PWM electric motor controller (using 4 field-effect transistors).

It was not possible to find an exact diagram, but this is not particularly required. Most likely, some of the mosfets burned out, because if the problem is in the microcircuits, you can immediately drain the water and look for a ready-made module on sale (may true radio amateurs forgive me for this heresy).

The hero of the occasion transistors were easily found, since they were short-circuited, but given their namelessness, the question arose of finding an analogue.

But you don’t need to think too much here: according to information from the blogs of repairers of these modules, MOSFETs from PWM power supply for PC processors and video cards are perfect here. Their current is approximately 30-40A, which is more than enough for a motor consuming 5-10A.

But there is one problem - it is almost impossible to solder them with a regular soldering iron, even a 100-watt one. They are soldered with refractory solders and most likely the result will be like mine:

I had to use a soldering station (hot air gun), after which things went well and the replacement of the burnt field wires was successfully completed. Next, look at the tests of the radio-controlled car after repair (and at the same time the tests of the recently purchased SONY HDR-250 video camera, since it’s simply a shame to continue shooting video for a YouTube channel with a 0.3 megapixel phone).

Video

As you noticed, it was additionally decided to install LED headlights with 2 LED 3 V, 300 mA connected through a 20 Ohm 1 W resistor to the battery. The connection is in series with a reduced current of 100 mA, so as not to overheat. This way it becomes clear that the car is on, and it’s a great pleasure to drive with them on a dark street!

In general, everything works as it should after repair, so the conclusion is this: almost all PWM regulators of RC models are built on mosfets, and when they burn out, we simply solder transistors from the boards of old non-working video cards with motherboards, of which you should have quite a few. Thank you all for your attention!

Discuss the article REPAIR OF SPEED CONTROLLER RC MODEL

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

Readers often ask questions about repairing dimmers with their own hands.

Therefore, I decided to supplement this information and highlight it in a separate article. Which you are reading now.

As always, there will be many photos with explanations, because it’s better to see once!

An example will be shown of how I repaired the dimmer with my own hands. There will be self-criticism and useful advice.

Causes of dimmer failures

Most often, the cause of failure may be exceeding the maximum permissible load or a short circuit in the load. Excess of load occurs when, for example, lovers of good lighting screw too powerful lamps into chandeliers. Or several lamps are connected through a dimmer, which in total consume too much power.

By the way, when choosing a dimmer, you should select the power with a margin of 30...50%. How to increase the power of a dimmer will be discussed and shown in this article.

A short circuit is possible not only due to faulty wiring. It happens that when light bulbs burn out, a short circuit (short circuit) occurs in them, the nature of which we will not delve into.

Malfunctions of dimmers on a triac

As a result of short circuit and overload, as a rule, triac fails. This is the main malfunction; it occurs in 90% of breakdown cases.

The triac is the main element. Its distinctive features are three terminals and a radiator screwed to the body. The most common models are BT137, BT138, BT139.

A faulty triac can be detected with a multimeter. If you test the resistance between terminals A1 and A2 (or T1 and T2, the first and second terminals) in ohmmeter mode, it will be from zero to several ohms. Conclusion - the triac has definitely burned out.

There is another case - the triac rings normally (infinite resistance), but the dimmer, however, does not work (the lamp does not light in all positions of the regulator). Only checking will help here, i.e. inclusion in a real circuit.

Replacing the triac will be discussed in detail below.

In addition to a faulty triac, there are other dimmer faults:

1. The power tracks of the printed circuit board burn out. This is a consequence of the main malfunction. The paths will have to be restored with jumpers.
2. The mechanical integrity of the regulator (potentiometer or variable resistor) is damaged. From frequent and intensive use, no explanation is needed here.
3. In dimmers that have a fuse, you must first check it before repairing. Often the manufacturer provides a spare one, which is stored in the same dimmer as the worker. Rational decision. If it had been in a separate bag, it would have definitely gotten lost.
4. Mechanical failure of contacts and soldering of the printed circuit board. First of all, soldering the contacts where the wires are screwed. It also happens that electronic elements are simply poorly soldered by the manufacturer.
5. Malfunctions of individual elements. First of all - dinistor, then resistors and capacitors.

Dimmer circuit

Before repairing, let's look at the dimmer circuit. Compared to the pro dimmer, I slightly reworked and clarified the circuit. In the last article I left the scheme the same. But in the new one, I did not change the numbering of parts, so as not to cause confusion.

The dimmer that we will repair has exactly this circuit.

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Dimmer repair procedure

Now I will give an example of how to replace a triac with your own hands, using a drill, soldering iron, and an ordinary toothpick.

The triac can be replaced by unscrewing the radiator and removing the triac from the board. But the radiator is now being riveted. The rivet is much more technologically advanced and cheaper in mass production.

Therefore, we pick up a drill with a drill with a diameter of 3.5...5.5 mm.

The arrow shows the direction of the drill.

2 Remove the radiator from the triac

The radiator has been removed, now you need to carefully remove the bad triac, causing minimal damage to the board. Recommended soldering iron power is 25 or 40 W.

3 Unsolder the triac from the board. The triac outputs are designated T1, T2, Gate.

Plus, a soldering iron requires experience and dexterity.

A soldering iron with a power of 60 Watts or more can easily damage the board.

The sites are stuck together, but that doesn’t matter yet.

And here are the triac friends, next to the DB3 dinistor:

The triacs (BT139, BT138, BT137) in the photo are all for a voltage of 800 Volts, the maximum operating current is 16, 12, and 8 Amps, respectively.

The datasheet can be downloaded at the end of the article.

Now we insert a new part into these through holes:

9 Trimming the legs (conclusions))

The jumper was unsuccessful, it was necessary to use thinner wires...

We carefully check the soldering to ensure there is no short circuit between the contact pads.

Now all that remains is to check the operation in a real connection circuit. Let me remind you that the dimmer is turned on in the same way as a regular switch:

For the test circuit, I use a light bulb of any power in a socket, a wire with a plug, and a terminal block.

Two more dimmers. Appearance of printed circuit boards.

Bonus – more photos:

Resistors are color coded. Have you learned how?

Dimmer circuit. Non-standard?

Download reference information on triacs for dimmers:

/ Datasheet, pdf, 183.12 kB, downloaded: 8915 times./

/ Datasheets, pdf, 150.55 kB, downloaded: 11810 times./

If you buy a triac, then on AliExpress in China these cost pennies, in this case 10 rubles per piece.

You also need to take into account the advantage of BTA triacs over BT - the BTA flange (radiator) is isolated from live parts, and this increases safety!

Similarities between dimmers and lamp protection units

I described lamp protection blocks that smoothly turn on the brightness of the lamps in detail in my articles about such blocks.

The difference between dimmers and BZ is only in the control method. In protection blocks, the triac is controlled by a controller according to the program. And the program can be anything, up to a wave-like change in brightness. Any analog or digital signal can be controlled. There would be demand.

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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.