How do capacitors go bad?
previous s did not mention age and heat. both dry electrolytes. bulbs are particularly prone to this because they are manufactured at low prices. my first repair company was replacing electrolytic in tube radios.
several reasons depending on the type of capacitor and its use, associated with environmental factors. surges, overload, mismanagement also play their role.
The most common is the dielectric failure due to aging, temperature, overvoltages and surges.
Oil or electrolyte leakage also causes the capacitor to dry out and fail. in salty weather, the aluminum housings are perforated by rust.
Many times, due to dust, dirt, moisture, and the formation of electrical traces of leakage between the terminals, resulting in a burn of the surface and an ultimate failure.
there are even more factors, but this sums up the most common. Increasing amplification of the home beer amplifier when I was a freshman, I played as often as possible on rock keyboards. Since I did not have any money, I built my own solid-state amplifier – a home-etch printed circuit board, hand-soldered through-circuit components, wired and heat dissipated output transistors , a case pierced by hand.
The amp seemed to work well – 60w RMS, seemed clean. What I did not know was that the poor layout of the printed circuit board and the external wiring had created an ultrasonic oscillation that I could not hear. this amp looked like a huge unstable opamp.
the design used a high value electrolytic capacitor to couple the output. One evening while studying, I happened to leave the thing lit up. Suddenly there was a loud noise, a stinking smell and smoke. the oscillation caused a thermal runaway in the output stage and blew off the top of the output coupling cap.
This is another way to quickly destroy capacitors (and expensive complementary output transistors).
There are two ways to determine the capacitance of a capacitor. Basically, a capacitor consists of two conductors separated by a non-conductor.
the capacity is determined by the surface of the driver that is presented to the surface that is presented to the non-driver.
If the driver is compromised and no longer drives, the capacitor loses its effectiveness. if the non-driver is compromised and becomes less non-conducting, then it becomes less efficient.
The capacitors become defective when the conductive parts become too low or the non-conductive parts get too high.
I have seen capacitors explode because they have become short and some have “opened up” to no longer be “there”.
Generally, capacitors fail because the dielectric goes down. its resistivity decreases, perhaps to the point of no longer isolating and even becoming conductive. An overpowering electric field in the capacitor can do this, and there may be a spark that burns through the insulation, leaving an open path or carbon trail.
In addition, the outer packaging of a capacitor may deteriorate or be damaged, so that moisture can enter the device. this could create a conductive path around the dielectric, making the device useless.
If one or both wires are broken, the unit will be irreparable.
Yet another failure mechanism is that the capacitor could be crushed, breaking it up and rendering it inoperative, or deforming it and changing its electrical characteristics.