Are 0.1uF 1% 16v Polystyrene available form any mainstream supplier? - Page 1
Forum section: electronics / projects

author: trys
author_rank: Regular Contributor
timestamp: February 25, 2018, 01:17:54 pm
content: Hi all,It appears that higher values than 0.022uF 1% Polystyrene capacitors seem to be very thin on the ground.Any ideas on where 0.1uF (1%, 16V or so) can be sourced from please?Thanks,Trys

author: Gyro
author_rank: Super Contributor
timestamp: February 25, 2018, 02:43:34 pm
content: I very much doubt it these days, Polypropylene has taken over for most higher value, low dielectric absorption, low leakage, applications.If you're specifically looking for one-off for a particular purpose, then you can find decent NOS ones from former Soviet Union ebay sellers but that's about it - by no definition mainstream!

author: SeanB
author_rank: Super Contributor
timestamp: February 25, 2018, 04:10:21 pm
content: Since 3M stopped making the polystyrene film they were made from many years ago there are now very few manufacturers of the film left, and thus the cost of the capacitors has gone up a lot along with the lead times. yes you will probably be better off with polypropylene, and in 0.1uF 16V will be a dicy thing anyway, the lowest I see polystyrene is 160V, as thinner films will be a lot more likely to have defects that only show up with time.

author: trys
author_rank: Regular Contributor
timestamp: February 25, 2018, 05:00:45 pm
content: Thanks both for your replies.You've confirmed in a way what I suspected, but I wasn't sure if I was searching in the right places.Am I right in thinking that the higher voltage ones will generally be of poorer tolerances? I've seen what I guess are suppression capacitors with higher capacity, but, say, 20% tolerances.There is a company in the UK called LCR components who do have some, but the prices, minimum order quantity and mailing costs makes it prohibitive.Trys

author: SeanB
author_rank: Super Contributor
timestamp: February 25, 2018, 07:28:48 pm
content: Nobody uses polystyrene as suppression, it was almost always used as precision values, or where you wanted low inductance from the extended foil types with the crimped foils, or where you wanted a capacitor that was pretty temperature stable, as stable as COG ceramic at least over the -30 to 70C range at least, but where you needed only to have commercial temperature range. Military range ones were always a lot larger, simply because the film softening point of around 70C meant you had to use thick films to survive 125C operation. 160V ones with 0.01% tolerance and up to around 2uF were available, but were expensive. Smaller values were common though, and tolerance was more due to selection during manufacture to get the close in values, the outliers being sold cheaply.Suppression are almost always polypropylene, polyester or something with high temperature capacity so as to survive self healing.

author: edavid
author_rank: Super Contributor
timestamp: February 25, 2018, 07:35:18 pm
content: I was surprised to see that Mouser stocks Xicon polystyrene capacitors... largest value is 0.01uF.https://www.mouser.com/Passive-Components/Capacitors/Film-Capacitors/_/N-9x371?P=1z0wpzo&Keyword=POLYSTYRENE&FS=True

author: floobydust
author_rank: Super Contributor
timestamp: February 25, 2018, 07:41:41 pm
content: I only know Xicon that makes polystyrene capacitors. Largest they offer is 0.01uF 50V is 10x12mm. Mouser is their large disti.Siemens, Mial, TRW, Rifa, Mallory etc. all dropped out of the business.There are Russian military parts K71-7 series that big (0.1-0.2uF PS) on eBay.edit: Lots of 0.1uF TEFLON hermetically-sealed parts as Russian military surplus, but they are 200-600V and huge.

author: Benta
author_rank: Super Contributor
timestamp: February 25, 2018, 07:45:34 pm
content: SeanB, thanks for the insights, I've not followed the passives market for some years.I remember the Philips pale green axial polystyrene precision caps from the 80s that were every audio buff's dream for active filters. IIRC, around 100 nF was max. value, and they were large.That polypropylene is the norm now is probably not a bad thing.

author: Kleinstein
author_rank: Super Contributor
timestamp: February 25, 2018, 09:18:53 pm
content: The PS caps have two major downsides: they don't like high temperature and they don't like some solvents. One big advantage is there low leakage, as the film goes all the way to the outside and no potting like with most PP caps. So one may still use < nF ones if pA matter.

author: Zero999
author_rank: Super Contributor
timestamp: February 26, 2018, 09:20:16 am
content: Quote from: trys on February 25, 2018, 01:17:54 pmJust one question: why?Nowadays it's very rare to need such a high capacitance, at such a tight tolerance. Is this an old design?

author: trys
author_rank: Regular Contributor
timestamp: February 26, 2018, 10:01:59 am
content: Yes, you are absolutely right!I'm trying to recreate a very low noise wien bridge oscillator which relies on the close tolerances of the capacitors used (and the two resistors).The higher the capacitance I can use for a given frequency also means I can use lower value resistors resulting in lower noise.I was considering paralleling caps, that would give me the increased capacitance and tolerance at the same time.I'm sure that there is a better way of doing it with modern capacitors, but at the moment I don't have enough experience to determine that.

author: Gyro
author_rank: Super Contributor
timestamp: February 26, 2018, 12:14:49 pm
content: In that case, you might want to take the ebay Russian capacitors route, there are some slightly sub-100nF ones around that you could then pad up to match with low value off-the-shelf Polystyrenes,eg.https://www.ebay.co.uk/itm/20x-0-1uF-0-0968uF-250V-2-K71-7-Russian-Polystyrene-capacitors-NEW/201612325213?hash=item2ef107f15d:g:95gAAOSwbYZXcUOm[Edit: orhttps://www.ebay.co.uk/itm/0-1-uF-250-V-LOT-OF-2-RUSSIAN-POLYSTYRENE-CAPACITORS-K71-7/272910264281?hash=item3f8ab827d9:g:IBkAAOSwfVpYtZ6k0.5%]

author: vk6zgo
author_rank: Super Contributor
timestamp: February 26, 2018, 12:27:34 pm
content: Back in the day, (1970s) they made polystyrenes up to somewhat higher values.We were refurbishing a Marconi TV Transmitter for PAL colour service.Part of this was a device called a "Sub Modulator", which amplified the incoming 1 volt video signal up to a level suitable to grid modulate the Tx RF Power Output stage.One part of this device used a couple of 0.47uF paper caps as coupling capacitors between stages.(The DC component was restored later).We swept the frequency response of the thing & it looked OK, but the old paper caps looked pretty cruddy.No problems, we'll just fit the two new 0.47uF polystyrenes.On sweeping the Sub-Mod again, the sweep looked like a "fish", with a nice big notch at around 3MHz.That's how we learnt that high capacitance Polystyrenes of that era, far from being ideal for HF work, had a substantial amount of self inductance.

author: trys
author_rank: Regular Contributor
timestamp: February 26, 2018, 12:46:14 pm
content: Quote from: edavid on February 25, 2018, 07:35:18 pmYes, I found them, but their tolerance are only 5%. Thanks for looking though, it's appreciated.

author: BravoV
author_rank: Super Contributor
timestamp: February 26, 2018, 01:12:04 pm
content: Have you ever consider those Russian's Silver Mica capacitor ?Also one of forum member Amspire did test these cap while ago ->HereSome of them do have tight tolerance, for example mine below came with 0.5% accuracy, bought these while ago at ebay directly from Russia, and the capacitance was spot on when scanned with my LCR.

author: amspire
author_rank: Super Contributor
timestamp: February 26, 2018, 01:16:15 pm
content: There are 2% Polypropoline capacitors 2% that cost about $1.30 and that will match each other to less then 1% over 40 degrees temp range.https://www.digikey.com/product-detail/en/vishay-bc-components/BFC241641004/BC2054-ND/502834At that price, you can buy 10 and find the best pair. The frequency will rise by about 0.5% going from 0 to 40 degC.You do not need accuracy - you just need a pair of capacitors to have matching values. It is true that the higher the accuracy, the more likely the capacitor will have a low temperature coefficient.There are still silver mica capacitors available and they can be extremely stable, but they cost a fortune for large values. I did pick up a bunch of 0.05uF 0.5% Russian silver mica caps years ago. The best mica comes from Russia so they can make great capacitors.This is the nearest I could find today:https://www.ebay.com.au/itm/2-X-Russian-Capacitors-SSG-1-40000pF-350V-0-5-MICA-SILVER-1978-OTK-2-PCS/312062224108?hash=iteThese are hermetically sealed in metal cans, so they are immune to humidity.They should make a great Wein Bridge oscillator.

author: Kleinstein
author_rank: Super Contributor
timestamp: February 26, 2018, 05:35:07 pm
content: Quote from: BravoV on February 26, 2018, 01:12:04 pmMica caps are quite different properties from polystyrene: they are more about a good TC and long time stability, but rather high dielectric absorption. For the bridge application this does not matter - for the bridge, the mica caps might be even better. I don't think it will need very good accuracy anyway - a simple adjustment pot could probably reduce the requirements to the usual +-10-20% range.

author: Zero999
author_rank: Super Contributor
timestamp: February 26, 2018, 06:42:28 pm
content: Use ceraminc C0G or polypropylene, which are both available in 1% tolerance, at a price of course and should be stable enough for your application.https://www.digikey.com/product-detail/en/kemet/C1206C104F5JAC7800/399-16900-1-ND/8346310https://www.digikey.com/product-detail/en/kemet/C350C104F1G5TA/399-14088-ND/6562499https://uk.rs-online.com/web/p/ceramic-multilayer-capacitors/7236600/https://uk.rs-online.com/web/p/polypropylene-film-capacitors/1666487/

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: February 27, 2018, 05:49:41 am
content: Hi,Try this one:https://www.westfloridacomponents.com/G147PE06/0.1uF+.1uF+50V+1%26%2337%3B+Molded+Epoxy+Capacitor+AVX+MR075A104FMA.htmlNot sure of the dielectric but it is 1%Also try Tedss they have various 1% .1ufhttps://www.tedss.com/Capacitors/Browse/film-axial?capacitance=100000.0&tolerance=1Cheers,Corby

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: March 01, 2018, 03:15:50 am
content: Hi,I was looking for some parts in my pile of junk boards and found two .1uf 100V 1% caps.They are maybe 1/2" Diameter and 1" long.If you want to pay shipping they are yours.Cheers,Corby

author: bson
author_rank: Unknown
timestamp: March 01, 2018, 07:07:53 pm
content: Quote from: trys on February 26, 2018, 10:01:59 amWhy do you need to match them for a Wien bridge? Typically, that's not required at all. 10% would be perfectly fine; you just need to accurately measure them.