Caps

[Ahakim]

Why electroyitic caps cause so much problems? dumb question?!

[mariushm]

Re: Caps

Because of the way they are constructed.

They have electrolytic inside, which is a substance that's liquid or semi-liquid and therefore:
1. it's prone to oxidizing the aluminum can that protects it from outside so the chemical composition changes

2. it can convert to gass or evaporates due to heat from outside

3. certain outside interferences (voltage over the capacitor rating, high pulses of current) can damage the layers of the capacitor and the electrolytic causing permanent or temporary damage. These interferences can also cause gas to form inside, causing the can to stretch and vent out the gas, but now the heat from outside the capacitor will dry out the electrolytic faster.

Other components are also affected by the above factors, but it's usually at a lesser degree.. or maybe these other components are not as common as capacitors.

For example relays can work just fine for years but the metal prongs that contact when the relay is triggered are slowly degrading due to oxidation and the electric arcs that happen naturally when the points come together and after a number of switches, they can fail or start working unreliably.

Just the same, potentiometers (think volume control) can oxidize and no longer work reliably after a while.

Anyway, electrolytic capacitors are used and are popular because they can offer a big capacitance in a low volume. There are ceramic capacitors, mica capacitors, tantalum capacitors, but these have other downsides or they can't be made to have the same capacitance as electrolytic capacitors (you won't easily find 3300uF ceramic capacitors, if there are any) or they're too expensive and dangerous to be feasible (tantalum capacitors for example, which are expensive and can explode or burn with big flames)

[PeteS in CA]

Re: Caps

They're designed, made and used by human beings with real world materials. The design can be defective. The manufacturing can be defective. They can wear out. They can be misused. They can be damaged by the failures of other components.