Fake primary capacitors

[tom66]

Okay, so I've had the joy of two L&C's to deal with. Same "300W" or "350W" design with about half the components "optional extra." Both of the supplies ended up under the crushing force of several bricks and my shoes, but before that I decided to pull some parts.

Found these primary caps by YC(?). Suspiciously, they all test around two E12 values below their rating - 330µF at ~220µF, 470µF at ~330µF. I found four that did this. (I tore one 470µF apart to see what made it tick, not much really, but the whole can was filled with paper and electrolyte, so that's something.) The 470µF cap was in the lower rated 300W supply.

These are -30% out of spec. Too consistent to be manufacturing tolerances, and outside of the -20% minimum.

ESR tested okay for primaries on all of these.

The "330µF" caps were in the PC with 100 Hz ripple on it. Needless to say I enjoyed the crushing sound of the PCB after that. (I saved the magnet wire and some ferrite cores for the coils.) With just 110µF (series total) of capacitance, it's no wonder the PSU had such high ripple. Amazing it ever worked at all.

It wouldn't surprise me if YC offered L&C a price too good to be true. I wonder if they ever bothered to test some of their components before installing them?

[dmill89]

Originally Posted by tom66

I wonder if they ever bothered to test some of their components before installing them?

L&C Take the time to test something. Why on earth would they do a thing like that?
Even if they did test low I doubt L&C would care. The fact that thy such low capacitance input caps shows that they aren't concerned with ripple or stability. I have a "400w" L&C that I pulled out of a cheap case with 2 330uf caps on the primary. This thing couldn't even run a K6-2 board when connected to MY UPS (modified sine wave), the power coming from this unit was so dirty that the fans would speed up and slow down. A pair of 680uf caps, Fuhjyyus believe it or not pulled from an Antec SP350 (I wasn't going to waste good caps on an L&C), fixed this problem but I still wouldn't trust that PSU on any modern system.

[Newbie2]

After seeing this thread, I decided to pull out my father's old BK Precision 875A tester and test a pair of cheap "KDC" 560uf 200V primary caps taken out of my brand-new generic "POWER PC" 350W power supply and BH 330uf 200V caps taken from my "Delta Power" 450W power supply when it was around a year old. This tester is still accurate, with random good 1000uf caps I tested were measured between 970uf and 1010uf.

The "KDC" caps claim to be 560uf in capacitance on the sleeve, but the tester says otherwise...


The first KDC cap I tested had 308uf, while the second cap was at 311uf. The measured ESR for both was at 0.05Ω.

And then the BH 330uf caps were not what they claimed as well...


The first BH cap I tested was at 203uf, while the other was at 204uf. The measured ESR was the same as the KDC caps.

Now, the KDC caps actually having 308-311uf is a large deviation from the claimed 560uf, as well as the BH caps having 203-204uf compared to their 330uf rating. Both caps are not old either, with the KDC caps being brand new pulls!

I guess we cannot trust cheap Chinese/Taiwanese primary capacitors.

[momaka]

Those results are indeed too consistent. I think the Chinese are manufacturing these caps properly (in terms of Chinese standards anyways) - i.e. the 470uF YC caps were probably designed and manufactured as 330uF but then labeled higher just so they can sell for a fraction of a penny more.

[b700029]

I remember reading about some absurdly tiny "4700uF" caps in PSUs (secondary) that were really 3300uFs.

It would be interesting to compare the weight and dimensions of these underrated caps with those that really have their true capacitance values.

The pattern seems to be
560uF -> 330uF
470uF -> 330uF
330uF -> 220uF

I've seen 680uFs in the gutless wonders too. Anyone have a few of those and a capacitance meter? I'm betting they'll be 470uF.

[ben7]

Wow what crap, I should see if i have any of these, and I might take them apart.

-Ben

[tom66]

The closest I have to the 470uF 200V is a 560uF 250V cap from a plasma TV.

It weighs about twice as much.

[Newbie2]

Originally Posted by tom66

The closest I have to the 470uF 200V is a 560uF 250V cap from a plasma TV.

It weighs about twice as much.

I had some genuine United Chemicon SMG 560uf 200V general-purpose caps ordered from Digikey that were used to replace the KDC 560uf 200V caps in my POWER PC 350W power supply, and the UCC caps felt like they had some weight to them in my hand. The KDC caps are as light as paper.

[tom66]

And the 560µF I have isn't even a "good" brand, just a Samyoung (but tests at 565µF.) Also, it's the same height as the "470µF", but about twice the diameter. A 100µF 400V Rubycon is about the same size, on a VCR power supply. So...

[severach]

I've found the same thing. The cheapo power supply input caps caps measure substantially lower than the label. I think it's because they know that the power supplies they are going into are still going to work at the lower capacitance.

[PeteS in CA]

Another thing that might be happening is some one bought cheap a bunch of surplus decently made, properly rated caps, removed the shrink-wrap sleeve and put on no-name sleeves with the capacitance rating bumped up, and sold them at a profit knowing they weren't likely to get caught.

My previous employer once considered buying what was purportedly a high-end ST Micro MOSFET which was in short supply from a non-authorized distributor. Purchasing was suspicious, so they got some samples and sent them for testing to the Component Engineering people (which included me). Not only could we tell the samples weren't what their markings said, but one of our tests told us that the parts were really a very decent, but older and not suitable for the product for which they would have been used, MOSFET made by IR.

[b700029]

Unfortunately it isn't easy to determine who originally made those caps, because electrolytics all look identical internally. Perhaps an analysis of the electrolyte composition may work, but manufacturers keep their compositions a trade secret. Only by comparing with known brands and series would that be any use. This might be another explanation as to why the vent stamps of cheap caps look like those of more expensive ones too.

[Newbie2]

This looks like a very good reason not to go all cheap and purchase some $30 "500W" power supply; they come equipped with components that don't live up to their ratings!

[PeteS in CA]

When I was at Delta Products our sales VP gave me a "250W" ATX cheap no-name to look over. It was enough to cure me of such cheap crap. I guesstimated it as actually good for maybe 120W-140W and spotted several glaringly obvious safety agency standard violations. Cheap crap is cheap because it's crap ... and it may prove to be expensive if you use it.

[Newbie2]

And now with decently-built power supplies from respectable brands (FSP, Seasonic, Antec Basiq series, etc.) that are priced between $40-$60, I believe their is really no reason to purchase $20-$30 gutless wonders. It is worth spending the extra $20-$40 (or more even) on a quality power supply, than to have hundreds of dollars worth of computer parts up in smoke by a gutless wonder.

[momaka]

Measured 2x 200V 330uF CapXon KM from 1999 the other day. They both showed 232uF and 228uF respectively - quite a bit low. Now, I understand they are old (I pulled them from the PSU they were in back in 2003), but still it seems that their capacitance is way too close to 220uF for this to be a coincidence. So perhaps CapXon is doing the same thing as these other crap manufacturers (i.e. marking the capacitance up)? I wouldn't be really surprised if they did.

[John Doe]

Originally Posted by Newbie2

And now with decently-built power supplies from respectable brands (FSP, Seasonic, Antec Basiq series, etc.) that are priced between $40-$60, I believe their is really no reason to purchase $20-$30 gutless wonders. It is worth spending the extra $20-$40 (or more even) on a quality power supply, than to have hundreds of dollars worth of computer parts up in smoke by a gutless wonder.

It's been that way for years. Long ago you could have gotten halfway decent units like CM Real Power's for that much, which were miles ahead of generic units.

I got a few old Topower's I'm now using as doorstop. I could re-cap, replace the fan and hell, even the transformer seems shoddy. But why bother? Today $50 can get you a SF Golden Green 450 unit which blows away many other PSU's that it just seems pointless to bother with crap units.

Originally Posted by momaka

Measured 2x 200V 330uF CapXon KM from 1999 the other day. They both showed 232uF and 228uF respectively - quite a bit low. Now, I understand they are old (I pulled them from the PSU they were in back in 2003), but still it seems that their capacitance is way too close to 220uF for this to be a coincidence. So perhaps CapXon is doing the same thing as these other crap manufacturers (i.e. marking the capacitance up)? I wouldn't be really surprised if they did.

Could be aged, or yeah, overrated. CapXon's are a notch below Teapo. Most units I've seen with CapXon's tend to have a wiggly shape of ripple, they just can't straighten it out. And they used to fail on Epsilon units.

[goodpsusearch]

Originally Posted by momaka

Measured 2x 200V 330uF CapXon KM from 1999 the other day. They both showed 232uF and 228uF respectively - quite a bit low. Now, I understand they are old (I pulled them from the PSU they were in back in 2003), but still it seems that their capacitance is way too close to 220uF for this to be a coincidence. So perhaps CapXon is doing the same thing as these other crap manufacturers (i.e. marking the capacitance up)? I wouldn't be really surprised if they did.

I have measured 1000uF Capxon and JunFu primary caps from my Jou Jye power supplies and they showed ~1000uF

[PeteS in CA]

momaka, I would think that while sitting on the shelf unused for a long time, the aluminum oxide layer might thin, resulting in a lower maximum voltage, but a higher capacitance.

[momaka]

Originally Posted by PeteS in CA

momaka, I would think that while sitting on the shelf unused for a long time, the aluminum oxide layer might thin, resulting in a lower maximum voltage, but a higher capacitance.

Maybe... but the ESR Micro V4.0 meter I used at work to test the caps showed otherwise. I tested several other capacitors (both HV and non-HV), and they all showed proper values. For example, a 450V 68uF CapXon from a TV made in 2006 was showing 66uF. Also, a 16V 1500uF Nichicon HN was showing 1510uF and 0.01 ESR. So I believe the meter is working right.

Perhaps the 200V 330uF CapXon KM's I have are fake ? Unlike regular CapXon KM which are black, these are dark blue with light blue for the (-) stripe.
But who knows. They are quite old too, so maybe that's the sleeve color CapXon decided to use at the time.