A swollen capacitor is a very common phenomenon that necessarily requires the replacement of a faulty capacitor and an examination of the circuits associated with it. Even if equipment with damaged capacitors is still working, this does not mean that it is in order.
Reasons for swelling of capacitors
The most common cause of swelling is the capacitor itself, which turned out to be of poor quality. The very same bloating occurs due to boiling or evaporation of the electrolyte.
Boil-off of electrolyte occurs at high temperatures, the source of which is both the external environment (heating devices near the equipment, objects closing the ventilation in the device, non-compliance with the operational characteristics of the device) and internal (poor-quality power supply, impulses to the capacitor, breakdown of the capacitor's insulation layer, non-compliance polarity, or the most common reason is a lack of electrolyte).
For capacitors, a temperature jump above 45 degrees is sufficient.
Evaporation of the electrolyte occurs if the capacitor has poor tightness (this is usually indicated by traces of corrosion from the electrolyte on the capacitor). Then, for some time, the electrolyte level will gradually decrease, which will inevitably lead to a change in the initial properties of the capacitor and, as a result, to the boiling of the remaining electrolyte, and then to the swelling of the capacitor. However, sometimes a poor-quality capacitor can be so poorly sealed that the electrolyte simply flows out through its bottom.
The electrolyte is used in electrolytic capacitors as a cathode (an electrode connected to a negative current source).
In any case, swollen and even corroded or poorly sealed capacitors must be replaced. Of course, the device containing them can still serve its user for some time, but soon failures will inevitably appear in its work.
Replacing swollen capacitors
If swollen capacitors are found, it is necessary to replace them, or to install additional high-frequency pulses for damping. It should be borne in mind that the rated operating voltage on the new capacitors should be no less than that of the swollen ones. The capacity of the new capacitors should also not be less than the replaceable ones, otherwise ripple will be skipped. In addition, it is worth observing the polarity if it is indicated on the board and the capacitor (otherwise, when the equipment is turned on, the newly installed capacitor may burst immediately).
To change modern capacitors that are small in size, it is better to use a thin soldering iron, since a more powerful one is able to quickly heat up the capacitors to a critical temperature, which will lead to their deterioration.