Caps going bad -- storage v.s. use

[garyrc]

Do caps in a crossover network go bad (get resistive, dry out, change value, whatever) faster when the speaker is being used, or when it is in storage? Does use or disuse affect them at all?

[twistedcrankcammer]

Do caps in a crossover network go bad (get resistive, dry out, change value, whatever) faster when the speaker is being used, or when it is in storage? Does use or disuse affect them at all?

A capacitor holds a charge until needed, not entirely unlike a battery. Capacitors go bad faster when left alone unused then when in constant use. Same as my 18 volt Dewalt drills 2 batteries, GGRRRrrr!! [N]

Roger

[garyrc]

Thanks, Roger.

What is the shelf life of caps before they are ever charged up or used at all?

[twistedcrankcammer]

Thanks, Roger.

What is the shelf life of caps before they are ever charged up or used at all?

That is like asking me what your expiration date is. Your genetics, environment, diet, exercise, many variables come into play.

There are many variables with capacitors; brands, size, qualitiy lines within the same brand, and type- oil filled, ceramic, different dielectrics.... etc...

If you have an overhead light in your living room that holds 5 seperate bulbs, do they all burn out at the same minute?, the same week?, the same month?, even the same year in many cases??

Roger

[Malcolm]

I have seen many types of capacitors fail. I have seen electrolytics turn into a cloud of aluminum foil. I have seen epoxy dipped tantalums turn into little orange sky rockets. And I have seen ceramic disk capacitors blow in half. All these were essentially cases of abuse.

Electrolytic capacitors (aluminum and tantalum) are the only type of capacitors that IMHO will definitely deteriorate over time, with perhaps the exception of the old paper capacitors (not paper in oil). In general, electrolytics will degrade faster on the shelf than in a working circuit.

The only electrolytic I have seen in a Klipsch crossover is the 33uF nonpolarized electrolytic in the E2 crossover in mid 80s Heresys. But there could be others. It was used because it was a good way to get a relatively large capacity at reasonable cost for a non-demanding application. There may be other models of Klipsch crossovers with electrolytics that I haven't seen.

Most of the heremetically sealed paper in oil capacitors used in older Klipsch speakers are probably as good as the day they were installed if the haven't leaked or been abused. Same goes for just about any of the film caps Klipsch has used in crossovers. But the only way you can tell for sure is to measure capacity, equivalent series resistance, and leakage current.

The only reason to replace anything other than an electrolytic that isn't obviously defective is to put something better in. Even then, you may not really hear a dfifference. I replaced that 33uF capacitor in the Heresy with a technically better, more expensive polypropylene cap, because it was just a matter of time before it failed. Can't say I could hear a difference, though. I replaced the 2uF motor caps used in the Type E crossover with high quality film caps. Can't say I heard a difference there, either. FWIW lots of folks say they hear an improvement when they replace caps.

[WMcD]

I have not seen any data tending to support a claim that keeping the crossover caps working (applying a.c. or d.c. voltage) will extend life, or that storage will hurt them. The ham radio crew would have reported it, I believe.

Power supply caps may be a different story, but even there I'm not convinced. You see reports about reforming the big power supply caps and I've put up an article on the fourm. It is more complicated than just bringing them up on a Variac. If you need to gently reform them, then maybe it is better to just keep them charged in the first place?

The concern may come from the practice of keeping a float charge on lead acid batteries.

Wm McD AB9BE

[Malcolm]

Deterioration of the oxide layer in idle aluminum electrolytics resulting in capacitance changes and increase in leakage current has been well documented for a very long time (1930s or earlier?). If the oxide layer is reformed before the process has progressed too far, the capacitor can be returned to nominal leakage current. If the process goes to far, it may not be possible to return to nominal. I suspect that the best modern electrolytics are less susceptible than older ones because of improved electrolyte formulas, but still susceptible because the whole design depends on maintaining a tightly control oxide layer thickness.

I cannot count how many pieces of electronic equipment I have rescued by replacing functioning, but degraded electrolytics, Electrolytics are like beer: you can't own them, only rent them.