Capacitor Identification - Page 1
Forum section: electronics / repair

author: andyfug
author_rank: Newbie
timestamp: August 24, 2016, 04:16:35 pm
content: Hello,Could you help me identify the capacitor pictured in the attachments?The text on the side says:50V1085°CA(M)1021I've looked online to try to understand this text, but I'm still not clear on how many F this capacitor is, since it doesn't seem to follow the standard notation (apologies if I've missed something obvious).The capacitor is inserted in series on the 'hot' audio signal line of this TRS 1/4" Jack connector. I have been supplied these before to remove DC bias (I'm led to believe, although my electronics knowledge is limited) on the high impedance audio signal line connecting an Electric Guitar to a Radio Transmitter Beltpack.Any help identifying the type and specs of this capacitor would be greatly appreciated.Many thanks,Andy

author: madires
author_rank: Super Contributor
timestamp: August 24, 2016, 04:25:00 pm
content: It's 10µF.

author: andyfug
author_rank: Newbie
timestamp: August 24, 2016, 04:30:11 pm
content: Quote from: madires on August 24, 2016, 04:25:00 pmMany thanks for your reply. What type would you believe it is? Polarised Electrolytic?Ta,A

author: madires
author_rank: Super Contributor
timestamp: August 24, 2016, 04:43:01 pm
content: Yes, polarised electrolytic cap. The white stripe (with the "-" symbol) at the side indicates the negative lead.

author: andyfug
author_rank: Newbie
timestamp: August 25, 2016, 05:43:33 pm
content: Many thanks for your help.

author: Twoflower
author_rank: Frequent Contributor
timestamp: August 25, 2016, 06:10:05 pm
content: If it's for audio usage I would change the cap. Instead a polarized cap I would go for an non polarized foil cap. It prevents problems with the wrong polarity and usually provides better linearity. I don't think the exact value matters much. And as foils are usually bigger you might not be able to squeeze a 10µF/50V foil in there. The minimum value depends on the impedance of the used equipment as the low frequencies are dampened more with smaller values. If you can give it a try it might be worth.

author: andyfug
author_rank: Newbie
timestamp: August 29, 2016, 04:53:46 pm
content: Quote from: Twoflower on August 25, 2016, 06:10:05 pmAhh... interesting. I'd need a bit of help working out what values to try (for the smallest physical cap size). Just so you know, we're connecting multiple guitars with varying impedances to this transmitter's input:http://www.shure.eu/dms/shure/products/wireless/user_guides/ur1m_user-guide-supplement_EN_650k/ur1m_user-guide-supplement_EN_650k.pdfBearing in mind the transmitter seems to have an input/load impedance of 200k? and the guitars will have output/source impedances between 100? for active pickups and 10k? for passive pickups, what do we think is the lowest value foil cap I could get away with (assuming lower capacitance = smaller size) and still get a frequency range of approx 20Hz - 20kHz through it?So you have the full picture, the reason for doing this at all is because of a problem we've had in the past where the odd guitar has produced an awful noise on radio packs when the volume pots on the guitars have been adjusted (typically on bass guitars with active pickups). We have used the cable pictured earlier in this thread (with the electrolytic cap in series on the audio signal line) to solve the issue before, but as Twoflower has suggested, maybe we should have a few different caps on hand to try out in the future to see if there is a tonal preference to any of them and to avoid wrong polarity.Let me know if you agree/disagree, but given the transmitter's wiring schematics in the PDF above and knowing that we are going to use TA4F connectors this time instead of Lemo connectors, I can't see us producing a DC bias onto the audio line by using only Pins 1&3 on a TA4F, like it seems we must have done with the Lemo connectors before (since the caps fixed our problems). Would the schematic suggest that there must have been a DC bias on Pins 1&3 of the Lemo connector? I'd rather have the caps around just in case, but I'm hoping that by using the TA4Fs this time, we shouldn't need them.Many thanks to you guys for your continued help.

author: madires
author_rank: Super Contributor
timestamp: August 29, 2016, 05:30:10 pm
content: The coupling cap plus the input impedance of the amp create a high pass filter. The -3dB cut-off frequency is f = 1 / (2 pi R C). R is the amp's input impedance and C the coupling capacitor. In your case the cap should be 47nF at least. Fitting a 100nF film cap in the plug shouldn't be any problem.

author: Twoflower
author_rank: Frequent Contributor
timestamp: August 29, 2016, 06:31:03 pm
content: Madires suggestion sounds reasonable. If you are willing to try out, you might build some short extension cords with an IC-socket in the hot line (only for this test, not permanent usage). This way you can plug-and-play the caps easily to see how the system behaves. But usually you need just a minimum size for the low frequencies.Otherwise I would look what the biggest capacity you could squeeze in there. 100nF are very small and would fit easily. And for example WIMA has the MKS-02 series caps. This series has a 1µF/63V cap with the size 5.5x10x4mm^3. That would be a frequency below 1Hz. But I'm not sure how easy it is to get them.I'm not sure what could caused that problem you saw with the bass guitars.

author: Planobilly
author_rank: Regular Contributor
timestamp: August 30, 2016, 03:41:29 am
content: Hi,I sometimes have trouble dealing with capacitors. I work on old analog gear at times and the codes are not always standard. There is a free software program that helps with some things that can be a bit hard to remember.http://www.freewarefiles.com/Electronics-Assistant_program_81382.htmlThe software would not have been any help with a cap that had 10 and no uf written on it. There are also cheap meters you can buy on ebay that work well enough in most cases and can tell you the value of a cap. Well...the meter could read most anything but if it read somewhere in the ball park of 10uf that would give you a clue at least. Another clue in your example would be the fact that it is an electrolytic cap defined by the round barrel shape and a stripe down one side. If the cap was new one leg would be shorter on the side with the stripe which is the negative side in almost all cases.There are many things in the Electronics Assistant software that are useful other than stuff abouts capacitors.Cheers,Billy

author: Merlot1970
author_rank: Contributor
timestamp: August 30, 2016, 11:03:05 pm
content: I would go with 10uf non-polarized.....Better ESR...Works better at higher frequency..

author: madires
author_rank: Super Contributor
timestamp: August 31, 2016, 12:17:36 pm
content: Could you please explain why a lower ESR would matter for an audio signal. Could you also elaborate on "better at higher frequency"?