Fake primary capacitors

[tom66]

Re: Fake primary capacitors

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

[Newbie2]

Re: Fake primary capacitors

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]

Re: Fake primary capacitors

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

It weighs about twice as much.

[ben7]

Re: Fake primary capacitors

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

-Ben

[b700029]

Re: Fake primary capacitors

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.

[momaka]

Re: Fake primary capacitors

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.

[Newbie2]

Re: Fake primary capacitors

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.

[dmill89]

Re: Fake primary capacitors

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.

[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 - 330uF at ~220uF, 470uF at ~330uF. I found four that did this. (I tore one 470uF 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 470uF 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 "330uF" 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 110uF (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?