Was it one of those days when the cat chewed your module? Or maybe you have an old amplifier with that nasty toxic goo leaking out of the capacitors? If you have ever been in this situation, then you could repair the module by replacing the capacitors. Let's look at an example where I replace this capacitor on a PCB. First, a little theory. What is a capacitor? A capacitor is an energy storage device that can be used to smooth out voltage. Each capacitor has two important parameters: capacitance and voltage. Capacitance tells us how much energy a capacitor can store at a given voltage. Capacitance is usually measured in microfarads (uF). In ninety-nine percent of cases, when replacing a capacitor, you need to use the same capacitance value or very close. A 470uF capacitor is used here. If I want to replace it, then ideally I should get another 470uF capacitor. Another important parameter is the rated voltage. The rated voltage is the maximum voltage at which the capacitor can operate without exploding. Once again, note that the voltage written on the capacitor means that this is the maximum voltage that can be applied to the capacitor. This does not mean that the capacitor will necessarily have this voltage. For example, this is a 16 volt capacitor. This does not mean that it is charged at 16 volts, like a battery. This means that if you charge it to 5 volts, it will work just fine. If I charge it to 10 volts everything will be fine. If I charge it to 16 volts, it can handle that too. But if I charge it to 25 volts, it will explode. Returning to our capacitor example, I see that it is rated at 16 volts. When replacing I must use a 16V or higher capacitor. Now it turns out that all the 470 uF capacitors I have are rated 25 volts. But it's not a problem. If in original scheme requires a 16V capacitor, then I can use a 25V capacitor, it just means I'll have more safety margin. Now let's talk about polarity. The negative side of an electrolytic capacitor will always have a small minus symbol on it. All you need to do is make sure the polarity matches the old capacitor. If you reverse the polarity, this is what happens. So now that I know the polarity, I'll replace the capacitor and solder it in place. Finally, a little safety warning. If you have ever seen these large capacitors at voltages greater than 200 volts, then you must be careful with them so as not to touch them if they are charged. Remember that a capacitor charged at 200V can kill you.
Happy capacitor replacement!
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Starting and running capacitors are used to start and operate electric motors operating in a single-phase 220 V network.
That's why they are also called phase shifters.
Installation location - between the power line and starting winding electric motor.
Symbol for capacitors in diagrams
The graphic designation on the diagram is shown in the figure, letter designation-C and serial number according to the scheme.
Basic parameters of capacitors
Capacitor capacity- characterizes the energy that a capacitor is capable of accumulating, as well as the current that it is capable of passing through itself. Measured in Farads with a multiplying prefix (nano, micro, etc.).
The most commonly used values for run and start capacitors range from 1 μF to 100 μF.
Nominal voltage of the capacitor - voltage at which the capacitor is able to operate reliably and for a long time, maintaining its parameters.
Well-known capacitor manufacturers indicate on its body the voltage and the corresponding guaranteed operating time in hours, for example:
- 400 V - 10000 hours
- 450 V - 5000 hours
- 500 V - 1000 hours
Checking the starting and running capacitors
You can check the capacitor using a capacitor capacitance meter; such devices are produced both separately and as part of a multimeter, a universal device that can measure many parameters. Let's consider checking with a multimeter.
- de-energize the air conditioner
- discharge the capacitor by short-circuiting its terminals
- remove one of the terminals (any)
- We set the device to measure the capacitance of capacitors
- We lean the probes against the terminals of the capacitor
- read the capacity value from the screen
All devices have different designations for the capacitor measurement mode; the main types are shown below in the pictures.
In this multimeter, the mode is selected by a switch; it must be set to Fcx mode. The probes must be inserted into the sockets marked Cx.
Switching the capacitance measurement limit is manual. Maximum value 100 µF.
This measuring device auto mode, you just need to select it, as shown in the picture.
The Mastech measuring tweezers also automatically measure capacitance, you just need to select the mode with the FUNC button, pressing it until the F indication appears.
To check the capacitance, we read its value on the capacitor body and set a deliberately larger measurement limit on the device. (If it's not automatic)
For example, the nominal value is 2.5 μF (μF), on the device we set 20 μF (μF).
After connecting the probes to the terminals of the capacitor, we wait for the readings on the screen, for example, the time to measure a capacitance of 40 μF with the first device is less than one second, with the second one more than one minute, so you should wait.
If the rating does not correspond to that indicated on the capacitor body, then it must be replaced and, if necessary, an analogue must be selected.
Replacement and selection of starting/running capacitor
If you have an original capacitor, then it is clear that you simply need to put it in place of the old one and that’s it. Polarity does not matter, that is, the terminals of the capacitor do not have the designations plus “+” and minus “-” and they can be connected in any way.
It is strictly forbidden to use electrolytic capacitors (you can recognize them by their smaller sizes, with the same capacity, and the plus and minus markings on the case). As a consequence of application - thermal destruction. For these purposes, manufacturers specially produce non-polar capacitors for operation in the circuit alternating current, which have convenient fastening and flat terminals for quick installation.
If the required denomination is not available, you can obtain it parallel connection capacitors. The total capacitance will be equal to the sum of the two capacitors:
C total = C 1 + C 2 +...C p
That is, if we connect two 35 μF capacitors, we get a total capacity of 70 μF, the voltage at which they can operate will correspond to their rated voltage.
Such a replacement is absolutely equivalent to one capacitor of larger capacity.
Types of capacitors
To start powerful compressor engines, oil-filled non-polar capacitors are used.
The housing is filled with oil inside for good heat transfer to the surface of the housing. The body is usually metal or aluminum.
The most affordable capacitors of this type CBB65.
To start less powerful loads, such as fan motors, dry capacitors are used, the housing of which is usually plastic.
The most common capacitors of this type CBB60, CBB61.
The terminals are double or quadruple for ease of connection.
Having decided to replace a capacitor on a printed circuit board, the first step is to select a replacement capacitor. As a rule, we are talking about an electrolytic capacitor, which, due to the exhaustion of its working life, began to create an abnormal mode for your electronic device, or the capacitor burst due to overheating, or maybe you just decided to install a newer or better one.
Selecting a suitable replacement capacitor
The parameters of the replacement capacitor must certainly be suitable: its rated voltage should in no case be lower than that of the capacitor being replaced, and the capacitance should not be lower, or maybe 5-10 percent higher (if this is permissible according to the rules known to you). scheme of this device) than it was originally.
Finally, make sure the new capacitor will fit into the space that its predecessor will leave. If it turns out to be a little smaller in diameter and height, it’s not a big deal, but if the diameter or height is larger, components located nearby on the same board may interfere or it will rest against the elements of the case. It is important to take these nuances into account. So, the replacement capacitor has been selected, it suits you, now you can start dismantling the old capacitor.
Getting ready for the process
Now it will be necessary to remove it from the board faulty capacitor, and prepare a place for installing a new one here. To do this, you will need, of course, and it is also convenient for this action to prepare a piece of copper braid for removing solder. As a rule, a soldering iron power within 40 W will be quite sufficient even if refractory solder was initially used on the board.
As for copper braiding to eliminate solder, if you don’t have one, it’s very easy to make it yourself: take a piece of not very thick copper wire consisting of thin copper strands, remove the insulation from it, lightly (you can use simple pine rosin) - Now these flux-impregnated veins will easily, like a sponge, absorb solder from the legs of the soldered capacitor.
Soldering the old capacitor
First, look at the polarity of the soldered capacitor on the board: which way is it facing minus, so that when you solder a new one, you will not make a mistake with the polarity. Usually the negative leg is marked with a stripe. So, when the braid for desoldering is prepared, and the soldering iron is already warm enough, first lean the braid against the base of the capacitor legs that you decided to free from solder first.
Carefully melt the solder on the leg directly through the braid so that the braid also heats up and quickly draws the solder from the board. If there is too much solder on the leg, move the braid as it fills with solder, collecting all the solder from the leg onto it so that the leg ends up free of solder. Do the same with the second leg of the capacitor. Now the capacitor can be easily pulled out by hand or tweezers.
Soldering in a new capacitor
The new capacitor must be installed in compliance with the polarity, that is, the negative leg is in the same place where the negative leg of the soldered one was. Usually the minus leg is indicated by a stripe, and the plus leg is longer than the minus leg. Treat the capacitor legs with flux.
Insert the capacitor into the holes. There is no need to shorten the legs in advance. Bend the legs slightly in different directions so that the capacitor stays in place well and does not fall out.
Now, warming up the leg near the board itself with the tip of the soldering iron tip, poke the solder towards the leg so that the leg is enveloped, moistened, and surrounded by solder. Do the same with the second leg. When the solder has cooled, all you have to do is shorten the legs of the capacitor with wire cutters (to the same length as the adjacent parts on your board).
The most common breakdown of modern electronics is the malfunction of electrolytic capacitors. If you, after disassembling the case electronic device If you noticed that there are capacitors on the printed circuit board with a deformed, swollen body, from which toxic electrolyte is oozing, then it’s time to figure out how to recognize a breakdown or defect in the capacitor and select an adequate replacement. Having professional soldering flux, solder, soldering station, with a set of new capacitors, you can easily “revive” any electronic device with your own hands.
In essence, a capacitor is a radio-electronic component, the main purpose of which is the accumulation and release of electricity for the purpose of filtering, smoothing and generating alternating electrical oscillations. Any capacitor has two most important electrical parameters: capacitance and the maximum direct voltage that can be applied to the capacitor without breakdown or destruction. Capacitance, as a rule, determines how much electrical energy a capacitor can absorb if a constant voltage not exceeding a given limit is applied to its plates. Capacitance is measured in Farads. The most widely used capacitors are those whose capacitance is calculated in microfarads (μF), picofarads (pF) and nanofarads (nF). In many cases, it is recommended to replace a faulty capacitor with a serviceable one that has similar capacitance characteristics. However, in repair practice there is an opinion that in power supply circuits it is possible to install a capacitor with a capacity slightly higher than the factory parameters. For example, if we want to replace a ruptured electrolyte with 100 µF 12 Volt in the power supply, which is designed to smooth out fluctuations after the diode rectifier bridge, we can safely set the capacitance even to 470 µF 25 V. Firstly, an increased capacitor capacity will only reduce ripple, which in itself is not bad for a power supply. Secondly, an increased voltage limit will only increase the overall reliability of the circuit. The main thing is that the space allocated for installing the capacitor is suitable.
Why do electrolytic capacitors explode?
The most common reason why an electrolytic capacitor explodes is excess voltage between the capacitor plates. It is no secret that in many Chinese-made devices, the maximum voltage parameter exactly corresponds to the applied voltage. According to their idea, capacitor manufacturers did not foresee that when a capacitor is normally included in an electrical circuit, the maximum voltage will be supplied to its contacts. For example, if the capacitor says 16V 100uF, then you should not connect it to a circuit where 15 or 16V will be constantly supplied to it. Of course, he will withstand such abuse for some time, but the safety margin will be practically zero. It is much better to install such capacitors in a circuit with a voltage of 10–12V, so that there is some voltage reserve.
Polarity of connection of electrolytic capacitors
Electrolytic capacitors have negative and positive electrodes. As a rule, the negative electrode is identified by the markings on the body (a white longitudinal strip behind the “-” signs), and the positive plate is not marked in any way. The exception is domestic capacitors, where, on the contrary, the positive terminal is marked with a “+” sign. When replacing capacitors, it is necessary to compare and check whether the polarity of the capacitor connection corresponds to the markings on the printed circuit board (the circle where there is a shaded segment). By matching the negative strip with the shaded segment, you will correctly insert the capacitor. All that remains is to cut off the legs of the capacitor, process the soldering points and solder them properly. If you accidentally reverse the polarity of the connection, then even a completely new and completely serviceable capacitor will simply rupture, simultaneously smearing all adjacent components and the printed circuit board with conductive electrolyte.
A little about security
It is no secret that replacing low-voltage capacitors can only be harmful to health if the polarity connection is incorrect. The first time you turn it on, the capacitor will explode. The second danger that can be expected from capacitors is the voltage between its plates. If you've ever taken apart computer power supplies, you've probably noticed the huge 200V electrolytes. It is in these capacitors that dangerous high voltages remain that can seriously injure you. Before replacing the capacitors of the power supply, we recommend completely discharging it either with a resistor or a 220V neon lamp.
Helpful advice: such capacitors really do not like to be discharged through a short circuit, so do not short-circuit their terminals with a screwdriver for the purpose of discharge.
In the element base of a computer (and not only) there is one bottleneck - electrolytic capacitors. They contain an electrolyte, the electrolyte is a liquid. Therefore, heating such a capacitor leads to its failure, as the electrolyte evaporates. And heating in system unit- this is a regular thing.
Therefore, replacing capacitors is a matter of time. More than half of the refusals motherboards middle and lower price category occurs due to dry or swollen capacitors. They break even more often for this reason. computer blocks nutrition.
Since the printing on modern boards is very dense, replacing capacitors must be done very carefully. You can damage and not notice a small unframed element or break (short) tracks, the thickness and distance between which is slightly greater than the thickness of a human hair. It’s quite difficult to fix something like this later. So be careful.
So, to replace capacitors you will need a soldering iron with a thin tip with a power of 25-30 W, a piece of thick guitar string or a thick needle, soldering flux or rosin.
If you reverse the polarity when replacing an electrolytic capacitor or install a capacitor with a low voltage rating, it may well explode. And here's what it looks like:
So, carefully select the replacement part and install it correctly. On electrolytic capacitors, the negative contact is always marked (usually vertical stripe color different from the body color). On the printed circuit board, the hole for the negative contact is also marked (usually with black shading or solid white). The ratings are written on the capacitor body. There are several of them: voltage, capacity, tolerances and temperature.
The first two are always present, the others may be absent. Voltage: 16V(16 volts). Capacity: 220µF(220 microfarads). These values are very important when replacing. The voltage can be chosen equal or with a higher nominal value. But the capacity affects the charging/discharging time of the capacitor and in some cases may have important for a section of the chain.
Therefore, the capacity should be selected equal to that indicated on the case. On the left in the photo below is a green swollen (or leaking) capacitor. In general, there are constant problems with these green capacitors. The most common candidates for replacement. On the right is a working capacitor, which we will solder.
The capacitor is soldered as follows: first find the legs of the capacitor on the back side of the board (for me this is the most difficult moment). Then heat one of the legs and lightly press the capacitor body from the side of the heated leg. When the solder melts, the capacitor tilts. Carry out a similar procedure with the second leg. Usually the capacitor is removed in two steps.
There is no need to rush, and there is no need to press too hard. The motherboard is not a double-sided PCB, but a multilayer one (imagine a wafer). Overdoing it can damage the contacts on the inner layers of the printed circuit board. So no fanaticism. By the way, long-term heating can also damage the board, for example, lead to peeling or tearing of the contact pad. Therefore, there is no need to press hard with a soldering iron either. We lean the soldering iron and press lightly on the capacitor.
After removing the damaged capacitor, it is necessary to make holes so that the new capacitor can be inserted freely or with little effort. For these purposes, I use a guitar string of the same thickness as the legs of the part being soldered. A sewing needle is also suitable for these purposes, but needles are now made of ordinary iron, and strings are made of steel. There is a chance that the needle will get caught in the solder and break when you try to pull it out. And the string is quite flexible and steel and solder adhere much worse than iron.
When removing capacitors, solder most often clogs the holes in the board. If you try to solder the capacitor in the same way that I advised you to solder it, you can damage the contact pad and the track leading to it. Not the end of the world, but a very undesirable occurrence. Therefore, if the holes are not clogged with solder, they simply need to be expanded. And if you do, then you need to press the end of the string or needle tightly to the hole, and on the other side of the board, lean the soldering iron against this hole. If this option is inconvenient, then the soldering iron tip should be leaned against the string almost at the base. When the solder melts, the string will fit into the hole. At this moment you need to rotate it so that it does not grab the solder.
After obtaining and expanding the hole, it is necessary to remove excess solder from its edges, if any, otherwise, during soldering of the capacitor, a tin cap may form, which can solder adjacent tracks in those places where the seal is dense. Pay attention to the photo below - how close the tracks are to the holes. Soldering this is very easy, but difficult to notice, since the installed capacitor interferes with the view. Therefore, it is very advisable to remove excess solder.
If you don’t have a radio market nearby, then most likely you can only find a used capacitor for replacement. Before installation, its legs should be treated, if necessary. It is advisable to remove all solder from the legs. I usually coat the legs with flux and tin them with a clean soldering iron tip, the solder collects on the soldering iron tip. Then I scrape the legs of the capacitor with a utility knife (just in case).
That's all, actually. We insert the capacitor, lubricate the legs with flux and solder. By the way, if you use pine rosin, it is better to crush it into powder and apply it to the installation site than to dip a soldering iron in a piece of rosin. Then it will work out neatly.
Replacing a capacitor without desoldering it from the board
Repair conditions vary, and changing a capacitor on a multilayer (PC motherboard, for example) printed circuit board is not the same as changing a capacitor in a power supply (single-layer, single-sided printed circuit board). You must be extremely careful and careful. Unfortunately, not everyone was born with a soldering iron in their hands, and repairing (or trying to repair) something is very necessary.
As I already wrote in the first half of the article, most often the cause of breakdowns is capacitors. Therefore, replacing capacitors is the most common type of repair, at least in my case. Specialized workshops have special equipment for these purposes. If you don’t have it, you have to use conventional equipment (flux, solder and soldering iron). In this case, experience helps a lot.
The main advantage this method is that the contact pads of the board will have to be subjected to much less heat. At least twice. Printing on cheap motherboards quite often peels off due to heat. The tracks come off, and fixing this later is quite problematic.
The disadvantage of this method is that you still have to put pressure on the board, which can also lead to negative consequences. Although from my personal experience I have never had to press hard. In this case, there is every chance of soldering to the legs remaining after mechanical removal of the capacitor.
So, replacing a capacitor begins with removing the damaged part from the motherboard.
You need to place your finger on the capacitor and, with light pressure, try to swing it up and down and left and right. If the capacitor swings left and right, then the legs are located along the vertical axis (as in the photo), otherwise along the horizontal axis. You can also determine the position of the legs by the negative marker (a strip on the capacitor body indicating the negative contact).
Next, you should press the capacitor along the axis of its legs, but not sharply, but smoothly, slowly increasing the load. As a result, the leg is separated from the body, then we repeat the procedure for the second leg (press from the opposite side).
Sometimes the leg is pulled out along with the capacitor due to bad solder. In this case, you can slightly widen the resulting hole (I do this with a piece of guitar string) and insert a piece of copper wire there, preferably the same thickness as the leg.
Half the job is done, now we move directly to replacing the capacitor. It is worth noting that the solder does not stick well to the part of the leg that was inside the capacitor body and it is better to bite it off with wire cutters, leaving a small part. Then the legs of the capacitor prepared for replacement and the legs of the old capacitor are treated with solder and soldered. It is most convenient to solder the capacitor by placing it on the board at an angle of 45 degrees. Then you can easily stand him at attention.
The resulting look is, of course, unaesthetic, but it works and this method much simpler and safer than the previous one in terms of heating the board with a soldering iron. Happy renovation!
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