Capacitor identification. - UK Vintage Radio Repair and Restoration Discussion Forum

joebog1 · 16th Feb 2019, 2:04 am

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

dazzlevision · 16th Feb 2019, 11:21 am

They are indeed Philips Polystyrene film close tolerance capacitors.

GrimJosef · 16th Feb 2019, 11:32 am

Quote:

Originally Posted by joebog1

... They look to me to be polystyrene ...

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

Radio Wrangler · 16th Feb 2019, 11:52 am

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

dazzlevision · 16th Feb 2019, 11:59 am

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

16th Feb 2019, 2:04 am	#1
joebog1 Banned Join Date: Jun 2015 Location: Mareeba, North Queensland, Australia Posts: 2,704	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 Attached Thumbnails

16th Feb 2019, 11:21 am	#2
dazzlevision Dekatron Join Date: Sep 2003 Location: Near Swindon, North Wiltshire, UK. Posts: 3,611	Re: Capacitor identification. They are indeed Philips Polystyrene film close tolerance capacitors.

16th Feb 2019, 11:52 am	#4
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,872	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 __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

16th Feb 2019, 11:59 am	#5
dazzlevision Dekatron Join Date: Sep 2003 Location: Near Swindon, North Wiltshire, UK. Posts: 3,611	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