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| Fake polypropylene capacitors from China? |
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| Wolfgang:
I may be mistaken, but "real" polystyrene caps are all NOS, because nobody makes them anymore. The ones I have are all "Styroflex" or the same from the former east block countries. Only moderate capacitance values, but very precise and no aging, leakage or dielectric soakage. Who makes new ones in the same quality and is trustworthy ? |
| spec:
--- Quote from: Wolfgang on January 23, 2019, 02:32:43 am ---I may be mistaken, but "real" polystyrene caps are all NOS, because nobody makes them anymore. The ones I have are all "Styroflex" or the same from the former east block countries. Only moderate capacitance values, but very precise and no aging, leakage or dielectric soakage. Who makes new ones in the same quality and is trustworthy ? --- End quote --- Polystyrene caps are rare nowadays because, in spite of their excellent electrical properties, they are relatively large, not compatible with SM, and are physically weak. They are also expensive. Another thing about polystyrene caps is that they always have very thin self-leads, which is not good for conductivity. We had a laugh at work when someone put a PCB with polystyrene caps through a wave-soldering machine ;D But they sound fantastic in audio equipment. They are also great for filters and RF work. Polystyrene caps are still made and are available new, as well as NOS: http://www.farnell.com/datasheets/1869697.pdf https://docs-emea.rs-online.com/webdocs/157e/0900766b8157e132.pdf https://www.hificollective.co.uk/components/polystyrene.html https://uk.rs-online.com/web/c/passive-components/capacitors/polystyrene-film-capacitors/ https://cpc.farnell.com/lcr-components/fsc-160v-6800pf/capacitor-160v-6800pf/dp/CA05867?mckv=sx5FCDr5d_dc|pcrid|224694277432|kword||match||plid||slid||product|CA05867|pgrid|48077370878|ptaid|pla-369572310414|&CMP=KNC-GUK-CPC-SHOPPING&gclid=Cj0KCQiAm5viBRD4ARIsADGUT262AYdYVQJKA_5bMf6IqW64RrYPHYJZFx2dTk0foLfqWodhA8AGKWgaAi58EALw_wcB https://www.cricklewoodelectronics.com/CPS1N0.html?gclid=Cj0KCQiAm5viBRD4ARIsADGUT26bDv85Gpj8QSzG5pFuL2AUnsafthr_8pY0w3q4UG248nHLpTZcEpsaAtWNEALw_wcB https://www.rapidonline.com/LCR-FSC160V220PF5-220pf-160V-5-Polystyrene-Capacitor-12-0522?IncVat=1&pdg=pla-339135155671:kwd-339135155671:cmp-757438067:adg-44804851896:crv-207912323492:pid-12-0522:dev-c&gclid=Cj0KCQiAm5viBRD4ARIsADGUT25yxfIuPlO_qi0wzVYSa61sawVb0rM1D-6whf7WzM-vPNlCzzKYvS8aAuGyEALw_wcB |
| Krampmeier:
Thank you for the links! I don't really need the stability of the polystyrene caps, but as the russion NOS seem to come at about the same price as new PP caps, I'll consider them. Will check the physical size difference first though. Does polystyrene really give an advantage over PP in the frequency range below 1 MHz? It will possibly still take some time until I actually buy parts because I am still working on the schematic and fighting with KiCad. I might order some different types for curiosity and will post results here once I get the parts. |
| spec:
--- Quote from: Krampmeier on January 23, 2019, 05:26:47 pm ---Does polystyrene really give an advantage over PP in the frequency range below 1 MHz? --- End quote --- In general polystyrene is best if you need the last gram of performance at low currents, say for a filter, or audio pre amplifier, but PP tends to be best if any appreciable current in involved. But there is not that much in it. They are both excellent caps. At one time, polycarbonate were the choice, but DuPont, or Bayer, etc stopped making the polycarbonate film. Wima made some really nice compact polycarbonate capacitors which were a good price too. At that time, I didn't bother with any other capacitor type, unless there was another overriding factor. They were little green beauties. |
| bson:
How many do you need??? Just buy real MKP parts from a trusted distributor. If they're for AC coupling then a 10% part is fine; the linearity of MKP will be far more important than the exact value. E.g., https://www.mouser.com/ProductDetail/Panasonic/ECW-FD2W105KB for a 10% part. $4.05 for 10. |
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