Capacitor failure modes

[analog_sa]

I hope someone can explain this as i certainly cannot. Two Sollen capacitors in a second order crossover have both gone open circuit but the Scanspeak tweeters are fine. Same failure in both speakers. Caps are rated at 250v and 400v DC. Really curious how two caps in series both go open circuit.

[kevinkr]

Originally Posted by analog_sa

I hope someone can explain this as i certainly cannot. Two Sollen capacitors in a second order crossover have both gone open circuit but the Scanspeak tweeters are fine. Same failure in both speakers. Caps are rated at 250v and 400v DC. Really curious how two caps in series both go open circuit.

There are known issues with certain vintages of Solen caps failing open, can you post pictures of the caps? Perhaps they fall into that range. (Ones with red epoxy on the ends for example)

For X-O duty I much prefer the Clarity SA over the Solen they just seem to sound more detailed/open without becoming obnoxious and they are in about the same price range.

[analog_sa]

Hi Kevin. Thanks for your explanation. The Solens are indeed the ones with the red epoxy. They belong to the crossover of a commercial speaker, i am not normally that cheap Do they fail open simply from old age? There are plenty more in that crossover...

[kevinkr]

Originally Posted by analog_sa

Hi Kevin. Thanks for your explanation. The Solens are indeed the ones with the red epoxy. They belong to the crossover of a commercial speaker, i am not normally that cheap Do they fail open simply from old age? There are plenty more in that crossover...

Yes, unfortunately that is exactly what they do, and the eventual failure rate seems to be very close to 100%. The only reliable solution is to replace them with something else..

[Ron E]

Originally Posted by analog_sa

Do they fail open simply from old age? There are plenty more in that crossover...

...perhaps bad internal connections ("foil" to leads?)

[kevinkr]

Originally Posted by Ron E

...perhaps bad internal connections ("foil" to leads?)

Actually these are metalized film types and apparently it is the chemistry/process of the metalization that is failing not the end terminations. This problem has been widely discussed here and elsewhere - the problem manifests itself in certain series of Solen caps from 20 or more years ago. There have been reports of newer ones infrequently failing as well - I have had at least one mid/late 1990s fail - cause undetermined.

I use them only in power supply applications IMHO they don't perform well enough sonically for use anywhere else.

[mondogenerator]

wow!

i knew i was better off avoiding boutique caps such as solens, and sticking to vishay polyesters, and bog standard HV PP caps.....even building capacitive dividers at work i have never had a cap go o/c, or even s/c..........

[kevinkr]

Originally Posted by mondogenerator

wow!

i knew i was better off avoiding boutique caps such as solens, and sticking to vishay polyesters, and bog standard HV PP caps.....even building capacitive dividers at work i have never had a cap go o/c, or even s/c..........

The_Solen_is_not_a_boutique_capacitor_IMHO.. It's just near bottom of the barrel commercial production, and just one of many brands out there. (It's a brand made by SCR - a French capacitor maker.)

I do specifically recommend the Clarity SA series for X-0 use and that's definitely a "boutique" cap in some quarters.

New Vishay film caps are good quality, and actually cost a good deal more around here than comparable Solens, but are widely available surplus at good prices. I use them too.