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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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16th Feb 2019, 2:04 am | #1 |
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Join Date: Jun 2015
Location: Mareeba, North Queensland, Australia
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Capacitor identification.
A quick question!
Does anybody recognise the construction type of the pictured capacitors? They look to me to be polystyrene, but they might also be some other type of plastic. I believe they were made by Philips in the 1960's or 1970's. I have set them up so one can see the value and the working voltage. I have many many values, but all are small. All values are small physically as shown by the rule. All values I have are 10mm in diameter and vary from 2.2 mm diamter to 5mm in diamter Can anybody help? Just on the side, using my new LCR meter they measure very accurately, within a few pF and show no leakage or absorption and "Q" is in the overload region. Joe |
16th Feb 2019, 11:21 am | #2 |
Dekatron
Join Date: Sep 2003
Location: Near Swindon, North Wiltshire, UK.
Posts: 3,621
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Re: Capacitor identification.
They are indeed Philips Polystyrene film close tolerance capacitors.
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16th Feb 2019, 11:32 am | #3 |
Dekatron
Join Date: Sep 2007
Location: Oxfordshire, UK.
Posts: 4,311
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Re: Capacitor identification.
Me too.
You might be able to discriminate between polystyrene and polyester if you were to warm them up. Polyester has a significant positive temperature coefficient whereas polystyrene has a smaller negative one http://www.interfacebus.com/Capacita...hange.html.jpg. I don't think it's safe to take polystyrene very hot though (85C max ?). Cheers, GJ
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16th Feb 2019, 11:52 am | #4 |
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Re: Capacitor identification.
Polystyrene capacitors have a temperature about 70C, somewhat below melting where they do a significant and irreversible value change. I used a lot of polystyrene capacitors in precision filter circuits of instruments that got environmental tests up to 55C.
Their normal tempco nicely corrects that of pot cores in Siemens N28 ferrite David
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16th Feb 2019, 11:59 am | #5 |
Dekatron
Join Date: Sep 2003
Location: Near Swindon, North Wiltshire, UK.
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Re: Capacitor identification.
Philips 424, 425, 426 and 427 series. 63, 160, 350 and 630Vdc working ranges. 1% or 5% tolerance. Full spec from page 88 here: http://mirror.thelifeofkenneth.com/l...r1981_text.pdf
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