capacitor polarity markings - Page 1
Forum section: electronics / beginners

author: GregDunn
author_rank: Frequent Contributor
timestamp: July 18, 2018, 10:49:36 pm
content: So weird to be posting in the Beginners thread, but I learn something every time I repair equipment, so I guess is some respect I'm still a beginner with every new piece of gear I work on...I've been installing and replacing capacitors for literally decades. The problem is that now caps are starting to come in packages which are unfamiliar to me. I've seen almost every kind I can think of - big aluminum cans, tantalum cans, gumdrops, axials, radials, etc. etc. and usually polarity is obvious - but my latest Digi-Key order came with these and I want to check and make sure I've decoded them right. I would expect the tapered end to be the+and the banded end to be the-, right?The only reasons I'm confused are that the data sheet shows both this package and the conventional aluminum can side by side, and they're depicted such that thenegativeend of the can is alongside thetaperedend of the other one. There are no legends indicating polarity for this particular package anywhere on the data sheet. Also, a quick google for aluminum electrolytics came back with images showing some with stripes indicating+and some with stripes indicating-!!!I'm sure there's actually a standard and that some of these pictures are just wrong - does someone have a copy of the standard or a clear description of how to interpret this particular package? This one is a D-K part 4201PHCT-ND if anyone cares.

author: Old Printer
author_rank: Frequent Contributor
timestamp: July 19, 2018, 01:10:23 am
content: I absolutely belong here in the beginner section so please take this with a grain of salt. Most of the polarized capacitors I have seen in the last couple years mark the negetive lead. Since this cap has a band on one end I would "guess" that to be the negetive lead. I would not be comfortable enough with my guess to install it that way so I would be looking for an answer myself. Curious to see how this plays out. Thanks for putting it here.

author: fpliuzzi
author_rank: Regular Contributor
timestamp: July 19, 2018, 01:27:43 am
content: Figure 2 of the attached data sheet depicts the tapered end as being positive. Hope this helps.

author: GregDunn
author_rank: Frequent Contributor
timestamp: July 19, 2018, 02:08:51 am
content: Quote from: fpliuzzi on July 19, 2018, 01:27:43 amHow did I miss that little + sign? Yes, that's clearly it.

author: fpliuzzi
author_rank: Regular Contributor
timestamp: July 19, 2018, 03:26:49 am
content: Quote from: GregDunn on July 19, 2018, 02:08:51 amThat + sign in the data sheet is pretty puny. I had to enlarge the pdf on my small laptop screen to see it clearly.

author: JS
author_rank: Frequent Contributor
timestamp: July 19, 2018, 03:41:00 am
content: My guess would been the stripe on the negative, pretty standard.But yes, they could make the datasheet more clear about that, I guess a little more black ink on the sign would be too expensive.JS

author: GregDunn
author_rank: Frequent Contributor
timestamp: July 19, 2018, 04:02:03 am
content: Apparently some capacitors (SMD and some of the smaller, square packages) really do have the stripe on the (+) end, which was part of what confused me. Look on this page under "polarity":https://en.wikipedia.org/wiki/Electrolytic_capacitor

author: vk6zgo
author_rank: Super Contributor
timestamp: July 19, 2018, 03:41:17 pm
content: Quote from: GregDunn on July 18, 2018, 10:49:36 pmInterestingly, that package is not a new style----I first saw it used in a Gates/Harris Modulation Monitor in the late 1970s.I never saw it anywhere else till now------I had started to think I imagined it!

author: Terry01
author_rank: Frequent Contributor
timestamp: July 19, 2018, 03:55:14 pm
content: Give it a quick test with your DMM in resistance mode. If it's the wrong way around it'll give you a negative measure. The correct way around will give you a positive measure.