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Re: Bad move imo

Posted by Jason Michael (A) on April 25, 2007 at 16:57:00

In Reply to: Bad move imo posted by nightdoggy on April 25, 2007 at 10:10:02:

Yes, the CJ polystyrene caps are Conrad Johnson's propriety caps and considered high quality, but i think the newer technology caps are equal or may be better that these caps. I've read that the polystyrenes poor heat resistance and they can be damaged by soldering ( http://my.execpc.com/~endlr/film.html ).. hmmm inside the amp is quite hot.:)

As for the resale ... i think the Premier 11a is a keeper and don't intend to replace ( as fo now ). Further more, the mod is reversible so if i plan to sell it in the future, i can just solder back the original styrene caps.

" Polystyrene:
Polystyrene (PS), (the Europeans often call it "styroflex" or "styrol") has long been the material of choice for critical analog circuits. Low leakage, low dielectric absorption and a shallow, flat temperature curve makes these capacitors suitable for timing circuits, filters, integrators, and sample-and-hold circuits. Moisture absorption is very low. Size, cost, availability, and temperature range limitations make polystyrene unsuitable for most other applications. Heat resistance is limited to about 85C, so forget surface mount. They can be damaged by soldering and by chlorinated board cleaning solvents. I don´t believe I have seen them in metallized film, only in film-foil.

Because of the poor heat resistance, polystyrene has largely been replaced by polypropylene and C0G ceramics, and the capacitor-grade film is no longer being made. There is several year´s supply still available, and they are still being sold, but be careful using them in new applications. Some manufacturers have noted that polystyrene caps are "not for new designs". One company, ITW Paktron, makes polypropylene capacitors with a guaranteed temperature drift similar to (if not quite as good as) polystyrene. PS's other electrical properties are mostly very similar to PP.

Whether polystyrene capacitors will really go away any time soon is not certain. I have been warned of polystyrene´s demise "in a few years" for over a decade now, and yet it is still available. There almost seems to be vast supplys of the film stashed away in manufacturers back rooms. It may also be that declining usage will extend available stocks for many years to come. I imagine that many of polystyrene´s traditional applications are fading away as newer technologies take over. "

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Analog Engineering Associates

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