Bad cap or bad measurement?

[wraper]

It's not a fake of the sort you linked to:
http://studioboytimes.tumblr.com/post/68565865754/a-fake-electrolytic

That 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.

[wraper]

I've thought a lot about it, and it's not just barely possible.  A DE-5000 can easily do it.

"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.

[wraper]

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.

[The Electrician]

I've thought a lot about it, and it's not just barely possible.  A DE-5000 can easily do it.

"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.

The 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.

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.

This 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.

[The Electrician]

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.

[The Electrician]

It's not a fake of the sort you linked to:
http://studioboytimes.tumblr.com/post/68565865754/a-fake-electrolytic

That 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.

Here are some fake radial capacitors:

http://makezine.com/2007/12/08/counterfeit-capacitors/

http://hobbyaudios.blogspot.com/2011/03/another-fake-capacitor.html

[wraper]

Here are some fake radial capacitors:

http://makezine.com/2007/12/08/counterfeit-capacitors/

http://hobbyaudios.blogspot.com/2011/03/another-fake-capacitor.html

Sorry 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=item19e7407fb3

http://www.ebay.com/itm/Sanyo-10V-1000uF-Low-ESR-Motherboard-Capacitor-x-5pcs-Japan-New-Free-Shipment-/140553662396?pt=Vintage_Electronics_R2&hash=item20b9a6afbc

This 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=item415be3e2c3

Whoa, 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=item35b5339ada

PCB 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

[Wh1sper]

Sorry 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/

Thank you didn't believe until today 
So if quality matters, no buy from ebay except trustworthy dealers?

[wraper]

Sorry 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/

Thank you didn't believe until today 
So if quality matters, no buy from ebay except trustworthy dealers?

It 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.

[wraper]

And he is selling Motherboard repair kit with obviously fake Rubycons as well
http://www.ebay.com/itm/Dell-GX280-Motherboard-Capacitor-Repair-Full-kit-/350426051001?pt=LH_DefaultDomain_0&hash=item51970531b9

[The Electrician]

Whoa, 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=item35b5339ada

This 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=0

But, 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.

[wraper]

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.

Problem 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.