What are the most causes of a dead capacitor? In other words, why can a capacitor be dead? Without getting into detailed specifics technical mumbo-jumbo and throwing a lot of terminology of how a capacitor is constructed, since start and run capacitors are constructed differently,I'll answer your question as directly as possible. If you'd like more detailed information, I will be glad to go into detail here or, you are welcome to email me. The capacitor momentarily stores a quantity of electrons causing one side to have a more positive side and the other side to have a more negative side, similar to a battery.
This is done by the way the capacitor is constructed and the materials used. Unlike a battery, a capacitor in an alternating current circuit does not constantly maintain the same polarity. You are probably familiar with the sine wave associated alternating current. The first half of the wave, the terminals on the capacitor assume a positive and negative charge.
On the second half of the wave, the charges are reversed. So in a 60 cycle circuit, this is happening 60 times. This eventually, over time, takes it's toll on the internal materials used to make the capacitor. Starting surges also take their toll on the longevity of a capacitor. The more the unit goes through a start cycle, the more taxing it is on the capacitor since there is some minute arching inside the capacitor. Some run capacitors have an internal fuse in them and once that blows, the capacitor has to be replaced since it is non-serviceable.
A charged capacitor can hold it's charge for a long time so handling them should be done with a knowledge of how to discharge them. Some capacitors have a "bleed" resistor connected between the terminals to help to discharge a capacitor. From experience.. Older capacitors, in my experience and opinion, are much hardier than newer capacitors. The problem with them, they were filled with liquid PCB. That would leak out and since it is labeled as a carcinogen, it is considered unsafe to humans and the environment.
That material is also used in large transformers. I know some guys who have frequently stood almost waist high in the stuff and never had any issues. I know others who have suffered very serious side effects.
As mentioned, this is a very high level explanation and I will surely give much more detail to you or anyone else who would like to know more. Just remember, a simple or "quick" question doesn't necessarily mean a simple and short answer. A capacitor is composed of two plates separated a piece of insulation material. The thinner the material, the higher the capacitance value created between the two plates.
The trick is to make the insulator as thin as possible in order to make the capacitor small. The problem is the insulator must withstand the voltage applied across the plates. Over time the insulation begins to break down due the electic field caused by the voltage potential across the plates.
When the insulation breaks down, a gas is released. You can spot a bad capacitor if the can looks swollen. A capcitor doesn't "die". What happens is the capacitance changes as the insulation begins to break down. If the plates touch each other, the capacitor becomes a short. This will not allow the compressor motor to start or run. Using a capacitor with a high voltage rating means the insulator has been reated to withstand a high voltage.
Using it at a lower rated voltage is not a problem. In theory the capacitor should have a longer life at a lower operating voltage. The PCB filled capacitors have 2 aluminum electrodes suspended into the liquid PCB, the length and thickness determines the rating.
The PCB allows electrons to flow from one electrode to another and aluminum chloride gas would immediately form around the electrodes acting as an electrical insulator, stopping electron flow through the liquid causing the capacitor electrodes to maintain one positive side and one negative side.
The negative side would flow discharge to the positive side through a closed circuit such as a fan or compressor. If it is a dual capacitor, a third electrode is suspended, sized according to the rating needed and a common terminal is used for both sides.
Momentary arching and the constant chemical changes eventually break down those capacitors. Many capacitors also have a marked terminal and attention should be paid as to where the marked terminal is connected. This is usually done with a red paint or ink dot.
Some capacitors, like those from GE, the writing that is stamped into the casing on one side, identifies that as the marked terminal. If not connected according to the marked terminal, the capacitor would still work. Over time, the electrodes would deteriorate chemically and electrically or the capacitor would leak. These type have a tendency to last much longer than the newer designs. The newer designs are made similar to electrolytics' but not exactly and, the chemical makeup has different properties so it can stay in a closed circuit indefinitely without consequences.
A start capacitor or, also called an electrolytic capacitor is constructed a bit differently. To visualize their make up, think of a sheet of waxed paper then a sheet of tin and another layer of waxed paper, another sheet of tin and another sheet of waxed paper. If you were to roll that up so it will fit into the round black casing, that is basically what is inside, with the terminals affixed to the tin.
Of course there are better things than waxed paper to insulate them but that gives you an idea of their make up. As mike home explained, the thickness of the tin and the length of the tin determine the rating. What is the difference between a start capacitor and a run capacitor? The start capacitor creates a current to voltage lag in the separate start windings of the motor.
The current builds up slowly, and the armature has an opportunity to begin rotating with the field of current. A run capacitor uses the charge in the dielectric to boost the current which provides power to the motor.
How do you size a run capacitor? Multiply the full load amps by 2, Divide this number by the supply voltage. The full load amps and the supply voltage can be found in the owner's manual.
The resulting number is the MicroFarad of the capacitor you need. Can I use a higher capacitance capacitor? What happens when capacitor is connected to AC? The capacitor is connected directly across the AC supply voltage.
As the supply voltage increases and decreases, the capacitor charges and discharges with respect to this change. A current will flow through the circuit, first in one direction, then in the other.
However, no current actually flows through the capacitor. Caveat emptor rules. Are low-Z caps higher quality? I'm about to do a bunch of repairs on some old motherboards You should be safe. Show 3 more comments. The Overflow Blog. Does ES6 make JavaScript frameworks obsolete? Podcast Do polyglots have an edge when it comes to mastering programming Featured on Meta.
Now live: A fully responsive profile. Linked 2. Related 2. Hot Network Questions. Probably not, at 0. They'll be fine. Gyro Super Contributor Posts: Country:. Quote from: silviasol on May 25, , pm.
Either way it hardly matters, this is a handheld video game, not mission critical avionics or something. The original dirt cheap crappy SMT electrolytic caps lasted what, 20 years before they started failing? Quote from: Richard Crowley on May 25, , pm. Quote from: silviasol on May 26, , pm. The caps are bad on just about every game gear now. Just search game gear capacitors, it is a huge issue. I went to a pawn shop to pick up two of them, they both had bad caps, one no sound and one the screen was dim like mine.
It was funny because the guy would not go lower on the price until I started to walk out of the store. Always liked that system, my little brother had one when we were kids. The only problem is the thing ate AA batteries like popcorn. Fortunately modern NiMH cells work pretty well.
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