Bad cap or bad measurement? - Page 1
Forum section: electronics / beginners

author: SpidersWeb
author_rank: Unknown
timestamp: July 23, 2014, 11:08:09 pm
content: So, I bought two sets of some 10uF 50V high current high frequency capacitors from two suppliers.Xicom +/- 20% 10uF 50V NP - looks cheap <--- both read 10.4uF on my multimeter in both polarities.NICHICON +/10% 10uF 50V NP - looks like a quality part <-- all FOUR of them read between 20.5 and 21uF (datasheet, part number, advert, and cap indicate 10uF)So before I ask for a refund and make aface - is it possible my meter is reading these caps wrong, or are they actually that far out of range?I'm just wondering if in certain circumstances (e.g. testing at say 1V on a 50V cap, or low current on something designed for high current etc etc) if it's possible to get incorrect readings??The Xicom went in circuit and is working 100%. I didn't bother trying the Nichicon's.

author: jamesglanville
author_rank: Contributor
timestamp: July 23, 2014, 11:43:33 pm
content: I may be entirely wrong on this, but I know some capacitors have a much lower capacitance at high voltages. Is it possible the nichicons are higher capacitance at low voltages to ensure they meet spec at higher voltages?

author: mariush
author_rank: Super Contributor
timestamp: July 23, 2014, 11:45:19 pm
content: NP means non-polar, they don't have polarity. Shouldn't matter how you connect the leads (and wouldn't matter normally anyway)High current and high frequency AND 10uF 50v don't go together. And NP capacitors are not really suited for high frequency...If you're not sure of your multimeter, you can always double check with a resistor and a power supply.Get a 5v or 12v or something below your capacitor's rating, put a 100k or something like that in series with the power supply and connect the capacitor, with the multimeter set on voltage and the leads connected on multimeter.. measure the time it takes to hit 2-3v on the capacitor. Then compare with other capacitors.

author: SpidersWeb
author_rank: Unknown
timestamp: July 24, 2014, 12:42:58 am
content: Quote from: mariush on July 23, 2014, 11:45:19 pmYeah it's for an almost 30 year old CRT. Not a part you'll find in stock at digikey/mouser/jaycar etc.The 10uF Xicom caps (which are working fine in the circuit and measured 10.4uF) came from an Arcade Electronics repair company in the US.The 10uF Nichion's that read 21uF came from a supplier on ebay.Datasheet for Nichion:http://www.mouser.com/ds/2/293/e-ha-5630.pdf(the ones which measured 21uF but label says 10uF)QuoteWould this be different to using the multimeter? Because I'm confident in the meter, I'm just not sure if the test conditions suit this particular capacitor.As in, was it common for some special use capacitors to show 2 x capacitance at low voltages - but act like a normal part in the conditions they were designed for?Quote from: jamesglanville on July 23, 2014, 11:43:33 pmThat's what I was wondering - maybe the Nichion's were specially designed for this type of circuit and this is a side effect?? I'd hate to return them and find out that's the case.

author: The Electrician
author_rank: Frequent Contributor
timestamp: July 24, 2014, 08:09:45 am
content: Try applying rated voltage to a Nichicon for several minutes, discharging, applying rated voltage in the other direction for several minutes, discharging and then measuring.

author: Wh1sper
author_rank: Regular Contributor
timestamp: July 24, 2014, 08:40:51 am
content: Your Multimeter is what?Standard Multimeters do an very simple Check with very low frequency while data sheet gives you +-10% for 120HzI think This is why you measure 21 µF I'm pretty sure the nichicon are the better ones to use.Read the datasheet :"Horizontal Deflection Current Correction Use"So they are guaranteed for your use case.

author: KedasProbe
author_rank: Frequent Contributor
timestamp: July 24, 2014, 08:51:22 am
content: Depending on your circuit there is a good chance that more than 10µF is better.

author: sfiber
author_rank: Regular Contributor
timestamp: July 24, 2014, 09:10:55 am
content: you should analyze to datasheets.Maybe capacitors that you ve bought from NICHION is specified for difference voltage and frequency values and your multimeter cant supply it.Some capacitors are only specified for only little range of frequency and voltage.At other ranges,capacitance of it can be changed

author: wraper
author_rank: Unknown
timestamp: July 24, 2014, 09:26:10 am
content: Who are those suppliers? Not ebay by chance?

author: KedasProbe
author_rank: Frequent Contributor
timestamp: July 24, 2014, 09:38:12 am
content: I was just thinking the model of a NP is two caps in series this means to get 10µF you need 2 of 20µF so my obvious reasoning is if one is shorted you get 20µF instead of 10µF.I could be wrong about this I don't know the NP cap design, I just thought I should mention it, so someone with NP cap experience can comment on it.

author: SpidersWeb
author_rank: Unknown
timestamp: July 24, 2014, 08:32:24 pm
content: Quote from: wraper on July 24, 2014, 09:26:10 amFor the Nichion - yep, ebay. That's kind of why I'm asking becuase I need to post feedback and/or request refund.8600 trades, packs of 4, arrived in a sealed static bag etc - looked quite professional - and there is full refund with 'seller pays return shipping'.I just don't want to be that ass who asks for a refund, says the product is bad, when it's my understanding that's lacking. Just wanted to double check with you guys.Quote from: Wh1sper on July 24, 2014, 08:40:51 amYep that's the kind of thing I was wondering.If being out by +100% at low freq/voltage is normal - I'll post positive feedback and keep them as special purpose spares.I'm just trying to work out if this is normal, or if they're garbage (but I don't want to re-open that CRT, desolder, and install the part just for testing).

author: wraper
author_rank: Unknown
timestamp: July 24, 2014, 08:46:10 pm
content: I would never buy capacitors on ebay, especially Japanese brands. Tear apart one of them to see if there isn't such a joke insidehttp://studioboytimes.tumblr.com/post/68565865754/a-fake-electrolyticAnyway very likely it is fake.

author: The Electrician
author_rank: Frequent Contributor
timestamp: July 24, 2014, 11:11:50 pm
content: Quote from: SpidersWeb on July 24, 2014, 08:32:24 pmCould you provide a link to that particular item on eBay?

author: SpidersWeb
author_rank: Unknown
timestamp: July 25, 2014, 01:30:07 am
content: Ebay link:http://www.ebay.com/itm/111289688665?_trksid=p3984.m570.l4467&_trkparms=gh1g%3DI111289688665.N19.S2.M-21748.R2.TR2All I know is my multimeter reads them as 21uF.

author: wraper
author_rank: Unknown
timestamp: July 25, 2014, 09:40:39 am
content: Can't find any mention of HF series (on ebay picture, NP is not series) in google. I searched by part number UHA1H100KHA which is given by seller, I foundLINKNot to mention that if you look it the datasheet how to decode part number, it shows that it is HA series part number.Well, actually I can find HF series (on picture) if search for NP, on aliexpresshttp://www.aliexpress.com/store/product/s-original-bags-nichicon-NP-bulky-electrolytic-capacitors-25v10uf-audio-Promise/527691_1618537992.htmlThat says a lot about their origin.

author: The Electrician
author_rank: Frequent Contributor
timestamp: July 25, 2014, 10:10:36 am
content: Check out this item the same guy has for sale:http://www.ebay.com/itm/2N3525-RCA-TO-66-VINTAGE-5A-SCR-TRANSISTOR-NOS-FREE-SHIPPING-/121381010466?pt=LH_DefaultDomain_0&hash=item1c42df3c22Seems a little pricey; am I missing something?

author: wraper
author_rank: Unknown
timestamp: July 25, 2014, 10:17:05 am
content: Quote from: The Electrician on July 25, 2014, 10:10:36 amLikely just out of stock, so rise up price until in stock again.

author: The Electrician
author_rank: Frequent Contributor
timestamp: July 29, 2014, 06:02:16 am
content: I ordered some of the caps from the eBay seller, made some measurements and here's what's going on.Here is a sweep showing capacitance on a linear vertical scale with zero at the bottom and 20 uF at the top; the green curve is capacitance and yellow is ESR (which is shown on the visible log scale). At low frequencies the capacitance is approaching 20 uF, but it decreases with increasing frequency, reaching about 10 uF at 100 kHz. At 15.85 kHz the capacitance is 11.76 uF, and even closer to 10 uF at frequencies approaching 100 kHz. Considering that this capacitor is designed to carry currents at the horizontal deflection frequency of a CRT video display, we might expect its capacitance to be the rated value at those frequencies and not at 120 Hz:The reason the capacitance decreases so much as the frequency increases is because this capacitor is made with aluminum foil that has been etched to increase the capacitance for a given can size.I discussed this here:https://www.eevblog.com/forum/testgear/mastech-ms5308-lcr-meter-with-esr-measurement-on-discount-at-the-moment/msg107489/#msg107489This article:http://www.kemet.com/Lists/TechnicalArticles/Attachments/191/Why 47 uF capacitor drops to 37 uF- 30 uF- or lower.pdfdiscusses the effect at length.The black curve in Figure 4 of that article shows the effect.My Fluke 187 DVM gives a capacitance measurement of 20.3 uF, and I would expect measurements made with DVMs to be similar.Making the measurement with an LCR meter at higher frequencies will give a much lower value. My DE-5000 at 100 kHz gives a value of 11.35 uF.So, there's nothing wrong with the cap; its capacitance when used at the horizontal frequency of a CRT display is much closer to 10 uF than 20 uF.

author: wraper
author_rank: Unknown
timestamp: July 29, 2014, 03:59:02 pm
content: 10 uf electrolitic capacitor rated at 100kHz? Give me a break, even this 1uF ceramic cap is rated at 1khzhttp://www.samsungsem.com/servlet/FileDownload?type=spec&file=CL10B105KO8NNNC.pdf

author: The Electrician
author_rank: Frequent Contributor
timestamp: July 29, 2014, 07:23:37 pm
content: Quote from: wraper on July 29, 2014, 03:59:02 pmThe spec sheet referenced in reply #3 says: "Designed specifically for horizontal deflection current correction of TV's where highfrequencies and high ripple currents are applied. "Horizontal frequencies of CRT based monitors are most likely in the range 10 kHz to 100 kHz.

author: wraper
author_rank: Unknown
timestamp: July 29, 2014, 08:39:01 pm
content: Quote from: The Electrician on July 29, 2014, 07:23:37 pmThere is no datasheet in post #3 but is datasheet in post #4 for HA which is different series, HF (OP's one) just don't exist in the nature (except aliexpress). But even if we are taking HA series, yes it says:QuoteHowever if you would read datasheet a little bit more carefully:Quote

author: The Electrician
author_rank: Frequent Contributor
timestamp: July 29, 2014, 10:07:23 pm
content: Quote from: wraper on July 29, 2014, 08:39:01 pmI didn't say that the spec sheet was referenced in post #3; I said it was referenced in reply #3. Look just below the subject line of each post after the first--the reply # is there.The OP seemed to think that the linked spec sheet might be relevant to the application for this cap even though it isn't the spec for the HF series. He says the cap goes in a 30 year old CRT. Apparently the HF series is obsolete, and probably was used to carry currents at the horizontal frequency of a CRT; the designation HF might have stood for "high frequency". I searched for a spec for a Nichicon HF series, but couldn't find one.Other evidence that this cap is intended to carry currents at frequencies substantially higher than 120 Hz is its physical size and its low ESR.A typical 10 uF, 50V electrolytic is nowhere near this big, and the ESR for this cap is around .1 ohm, more or less, in the vicinity of 10s of kilohertz. If the cap is carrying 3 amps, for example, the dissipation in the cap would be around 1 watt. A more typical 10 uF electrolytic has an ESR of several ohms.The large physical size of this cap allows it to dissipate 1 watt without any problem.Quote from: wraper on July 29, 2014, 08:39:01 pmI read it carefully enough to see that the spec is, strictly speaking, for the HA series, not the HF series.If we could find an actual spec sheet for the HF series, it might specify the capacitance at 15.75 kHz, or even higher. That would make sense, since they obviously used heavily etched foil to make this cap. Perhaps the HA series didn't use etched foil, and its capacitance doesn't vary 2 to 1 as the measurement frequency increases toward the SRF.As I said above, even though the spec sheet is for the HA series, the description of a capacitor designed to carry horizontal frequency currents would seem to be applicable, even if perhaps not exact in every respect.You seem to be missing the point of my post. The point I was making is that if the Nichicon cap is intended to operate at frequencies above 10 kHz, the capacitance at those frequencies is what we care about, and it's nearer to 10 uF than it is to 20 uF. The capacitance measured by a DVM (they effectively measure at a very low frequency), or by an LCR meter at 120 Hz is not really relevant to use of the capacitor at horizontal deflection frequencies. The capacitance marked on the cap is correct if the measurement is made at a much higher frequency than 120 Hz.The OP wondered why his meter gives a value of about 20 uF when the value marked on the cap itself is 10 uF. I gave him an explanation.

author: wraper
author_rank: Unknown
timestamp: July 29, 2014, 10:30:03 pm
content: Explanation is that it is just a Chinese fake of non existing series. One should know that it is much easier to buy fake capacitor than genuine one on ebay/aliexpress (and any mention of it exists only there). Especially if it is some rare and expensive one, and non polar ones are of such kind. Show me a single datasheet for electrolitic capacitor where capacitance is specified in kHz range. If you would think a little bit, then you would understand that it is barely possible to measure such capacitance at 100kHz frequency. Capacitive reactance for 10uF capacitor is 0.16 Ohm at 100 kHz and 1.6 ohm at 10 khz. For such capacitors ESR usually is >1 Ohm. How do you expect to reliably measure capacitance in conditions when ESR prevails over capacitive reactance by order of magnitude?

author: The Electrician
author_rank: Frequent Contributor
timestamp: July 29, 2014, 10:52:26 pm
content: Quote from: wraper on July 29, 2014, 10:30:03 pmI've thought a lot about it, and it's not just barely possible. A DE-5000 can easily do it.Reply #17 shows the result of such a measurement over a 100 Hz to 1 MHz span.Quote from: wraper on July 29, 2014, 10:30:03 pmI expect to use an instrument that can measure capacitance and ESR when ESR and capacitive reactance are more than 3 orders of magnitude different, such as these:http://www.waynekerrtest.com/global/html/products/LCR/6430%206440.htmhttp://www.home.agilent.com/en/pd-715495-pn-E4980A/precision-lcr-meter-20-hz-to-2-mhz?cc=US&lc=enghttp://www.hioki.com/products/lcr_resistance_signal/lcr_resistance_meters/654

author: The Electrician
author_rank: Frequent Contributor
timestamp: July 29, 2014, 11:05:48 pm
content: Quote from: wraper on July 29, 2014, 10:30:03 pmIt's not a fake of the sort you linked to:http://studioboytimes.tumblr.com/post/68565865754/a-fake-electrolyticI opened one up, and it doesn't appear to be a fake at all. It's well built and reminds me of a photoflash capacitor. The internal foil pak fits tightly into the can, to give good thermal connection to the can:

author: wraper
author_rank: Unknown
timestamp: July 29, 2014, 11:46:18 pm
content: Quote from: The Electrician on July 29, 2014, 11:05:48 pmThat was written thinking that it is an axial capacitor before ebay link was given. With radial ones they don't need to make some obscure things as radial capacitors are widely available.

author: wraper
author_rank: Unknown
timestamp: July 30, 2014, 12:00:49 am
content: Quote from: The Electrician on July 29, 2014, 10:52:26 pm"Easily", only single 10uF cap which my DE5000 was able to measure (showing something) at 100 kHz was big 250V one (likely lower ESR). It wasn't able to measure any 10 uF cap with lower voltage rating (smaller size = higher ESR), nor any with higher capacitance.Sure you can measure with ultra expensive equipment. But what the point, there is no use for capacitance as parameter at such frequency. It does not mean anything. At such frequency you usually care only about ESR and max ripple current, maybe some other parasitic parameters at specific uses.

author: wraper
author_rank: Unknown
timestamp: July 30, 2014, 12:05:58 am
content: As this is non polar one, I would suggest to test at full rated voltage in both directions for at least 30 minutes, maybe even measuring current in process. That might be 22 uF polarized high voltage capacitor as well. Explanation might be they just didn't found big enough 10 uF polarized capacitor to make NP one from it, so they just took 22 uF.

author: The Electrician
author_rank: Frequent Contributor
timestamp: July 30, 2014, 02:49:27 am
content: Quote from: wraper on July 30, 2014, 12:00:49 amThe highest useable range of the DE-5000 at 100 kHz is the 20 uF range, and the spec says 3% error only below 10 uF. I mentioned in another thread where I compared the DE-5000 to the Wayne-Kerr that the DE-5000 was having problems for caps 10 uF and larger.However, my DE-5000 has no problem with 10 uF caps at 100 kHz. If it gives any display at all, it can resolve the real and imaginary parts of an impedance with 2 orders of magnitude difference. To show this, I connected a 50 ohm trimpot in series with the cap so I could artificially increase the ESR. With as much as 20 ohms additional, the DE-5000 is still within 5%. You have to use very short leads, and perform the open/short cal procedure.Quote from: wraper on July 30, 2014, 12:00:49 amThis very thread is an example of where the value of capacitance at over 10 kHz matters. It's not true that it doesn't mean anything. The value of the capacitor is coordinated with an adjustable inductor. The tuning need not be very precise, but a capacitor 2 times too large might mean that the adjustment range wouldn't be what it should.

author: The Electrician
author_rank: Frequent Contributor
timestamp: July 30, 2014, 03:00:38 am
content: Had the OP done what I suggested in reply #4, we wouldn't be having this discussion.I carried out the procedure described in reply #4, and now the impedance analyzer sweep is like this:The capacitance is nearly flat with frequency and equal to 10 uF, although I still see a little bit of the decrease with frequency due to etched foil.I also got this same result with another one of the caps by applying a 50 volt peak, 60 Hz sine wave from a transformer driven by a variac.The reformed cap measures 10.7 uF on my Fluke 187 DVM.So all the OP need do is follow the procedure in reply #4 and all should be well. Simply installing in the CRT equipment and powering it up would probably do the job too. It might take a minute or so to settle down to a final value.

author: The Electrician
author_rank: Frequent Contributor
timestamp: July 30, 2014, 03:05:17 am
content: Quote from: wraper on July 29, 2014, 11:46:18 pmHere are some fake radial capacitors:http://makezine.com/2007/12/08/counterfeit-capacitors/http://hobbyaudios.blogspot.com/2011/03/another-fake-capacitor.html

author: wraper
author_rank: Unknown
timestamp: July 30, 2014, 09:58:17 am
content: Quote from: The Electrician on July 30, 2014, 03:05:17 amSorry but such fakes are very rare. Usually they look pretty like genuine ones outside/inside. It is easily to distinguish them only if counterfeiters made a mistakes. Very often a vent shape do not match.http://www.shenzhen-standard.com/2010/09/13/beware-of-counterfeit-capacitor-products/There is shitload of capacitors with X vent on the market, so to make nichicon you only need to print a new sleeve.Searched on ebay, appears that crap sellers became smarter, vent is visible only on small amount of pictures. And almost all of them of right shape what doesn't mean they are genuine of course. Even a year ago I was able to spot a shitload with wrong vent shape on pictures almost instantly.Fake Sanyo (wrong vent) which eevblog member bought on ebay. Failed after a couple of months of use.I even have seen fake 2N3055 myself with 10x smaller than genuine die inside.Had a tough time to find capacitors with a wrong vent that is shown on picture, but here they are (must be K vent):http://www.ebay.com/itm/3x-SANYO-330UF-330MFD-100V-CE-Elec-Alum-Radial-Cap-Low-ESR-16X33mm-105DEG-/111253946291?pt=LH_DefaultDomain_0&hash=item19e7407fb3http://www.ebay.com/itm/Sanyo-10V-1000uF-Low-ESR-Motherboard-Capacitor-x-5pcs-Japan-New-Free-Shipment-/140553662396?pt=Vintage_Electronics_R2&hash=item20b9a6afbcThis is very obvious one, even printing color is crappy:http://www.ebay.com/itm/50p-SANYO-25V-1000UF-Electrolytic-Capacitor-10X20mm-/280714535619?pt=LH_DefaultDomain_0&hash=item415be3e2c3Whoa, proudly US SELLER who sells counterfeits and sold ton of them according to the listing.http://www.ebay.com/itm/16V-3300uF-105C-10-x-24-mm-Low-ESR-Sanyo-Capacitors-New-5-Pcs-/230673324762?pt=LH_DefaultDomain_0&hash=item35b5339adaPCB full of fake capacitors:http://www.ebay.com/itm/DIY-Kit-8x2200uF-35V-SANYO-capacitor-Array-Power-Amp-filter-circuit-board-/221267458586?pt=US_Amplifier_Parts_Components&hash=item3384917a1a

author: Wh1sper
author_rank: Regular Contributor
timestamp: July 30, 2014, 10:15:58 am
content: Quote from: wraper on July 30, 2014, 09:58:17 amThank youdidn't believe until todaySo if quality matters, no buy from ebay except trustworthy dealers?

author: wraper
author_rank: Unknown
timestamp: July 30, 2014, 11:36:40 am
content: Quote from: Wh1sper on July 30, 2014, 10:15:58 amIt is hard to tell who is trustworthy one. If you received good looking fake it likely won't fail instantly. Therefore feedback may be excellent while seller actually sells crap. I see it from a such point: am I ready to skimp 10 cents on 5% possibility (likely higher) that I will get fakes which will go into some device. I buy only otherwise unobtanium or what I will be able to verify by almost 100% (still might be knockoff IC that appears to work exactly the same). And frankly receive crap quite often actually, however most people won't be able to distinguish them.And yeah, talking about being trustworthy, that us seller sold a LOT of counterfeit capacitors, yet no single negative feedback saying about that.

author: wraper
author_rank: Unknown
timestamp: July 30, 2014, 11:46:06 am
content: And he is selling Motherboard repair kit with obviously fake Rubycons as wellhttp://www.ebay.com/itm/Dell-GX280-Motherboard-Capacitor-Repair-Full-kit-/350426051001?pt=LH_DefaultDomain_0&hash=item51970531b9

author: The Electrician
author_rank: Frequent Contributor
timestamp: July 30, 2014, 03:22:57 pm
content: Quote from: wraper on July 30, 2014, 09:58:17 amThis seller has some other caps that have the proper "K" vent.http://www.ebay.com/sch/m.html?_odkw=capacitor&item=230673324762&pt=LH_DefaultDomain_0&_osacat=0&_from=R40&hash=item35b5339ada&_ssn=cciecollaboration&_trksid=p2046732.m570.l1313.TR0.TRC0.H0.Xcapacitor+sanyo&_nkw=capacitor+sanyo&_sacat=0But, notice that the ones with the "X" vent are a slightly different color than the ones with the "K" vent. Of course, nothing prevents the makers of fakes from using a "K" vent.The shape of the rubber seal can also help distinguish fakes.The OP's Nichicon caps were thought to be possible fakes because their capacitance was too large. But now that I've shown that reforming will restore the proper capacitance, that anomaly is no longer evidence of fakery.They have the proper shape rubber seal, the vent has the proper configuration, and the internal construction appears to be very high quality. I don't think they're fakes.I hope the OP will do the reforming procedure I described in reply #4 and let us know if the capacitance then becomes ~10 uF.

author: wraper
author_rank: Unknown
timestamp: July 30, 2014, 04:55:13 pm
content: Quote from: The Electrician on July 30, 2014, 03:22:57 pmProblem with nichicons is that half of all capacitors made in the world are with such vent. You only need to apply new sleeve on the readily existing cheap general purpose capacitors to make ultra low ESR, NP or whatsoever. Insides looks like just usual capacitor. I don't believe in miracles since childhood, so if such capacitor series exist only on aliexpress and nowhere else and capacitance is wrong and very close to 22uF value, possibility that it is a fake is much higher that it requires forming.