Author Topic: [First post] Fake x2 capacitors?  (Read 1128 times)

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Offline james_s

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Re: [First post] Fake x2 capacitors?
« Reply #25 on: April 21, 2017, 12:47:55 PM »

I was trying to point out that weird hole/bubble below the right leg.

That's an air bubble on the surface of the epoxy potting. Not exactly a sign of extremely high quality but not necessarily a problem either.
 

Offline Gyro

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Re: [First post] Fake x2 capacitors?
« Reply #26 on: April 21, 2017, 11:26:57 PM »
How many posts does it take to tell a newbie -  Don't buy safety critical parts on ebay, buy them from a reputable distributor. Simple as that!  ::)
« Last Edit: April 21, 2017, 11:29:32 PM by Gyro »
Chris

"Victor Meldrew, the Crimson Avenger!"
 
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Offline Fungus

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Re: [First post] Fake x2 capacitors?
« Reply #27 on: April 21, 2017, 11:38:02 PM »
Isn't everything sold on ebay fakes or rejects? That is how they have very cheeeep prices and frequently the shipping from China is free.
I support my local REAL parts distributors who sell genuine items at reasonable prices.

Not everything, no.

But ... it's almost impossible to tell from the adverts and/or prices of stuff. Mostly the sellers don't even know what they're selling. I've bought the same stuff twice from the same seller via the same advert. One batch was perfect, one batch was junk. Go figure.

(I think some sellers advertise stuff then go downtown to get some if anybody buys. You'll get is whatever is in the market that day).

The real trick with eBay is to underpower and overrate everything. If you need a 10W power supply, order a 20W supply and you'll probably be fine. Need a 10W LED? Buy a 20W LED and underpower it. etc.

Or... buy from Russia/Israel. Those guys usually have quality stuff, but you'll pay for shipping.
« Last Edit: April 21, 2017, 11:41:27 PM by Fungus »
 

Offline RukyCon

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Re: [First post] Fake x2 capacitors?
« Reply #28 on: April 21, 2017, 11:54:53 PM »
There seems to be a few mixed opinion's about the x2 caps, i have some people telling me that i should not use ones from eBay, but then i have some people telling me that there most likely ok to use.

And i'm not the type of person that buys all of there parts from eBay. example: i was repairing an old power supply [some of the output caps had failed] and i got all of the parts to do it off of mouser.
 

Offline Siwastaja

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Re: [First post] Fake x2 capacitors?
« Reply #29 on: April 22, 2017, 02:32:24 AM »
i have some people telling me that i should not use ones from eBay, but then i have some people telling me that there most likely ok to use.

No really, this is almost a tradition on the EEVblog forum now, so I guess many people don't even feel like commenting anymore.

Anyone who really has used Ebay to source their components, and really used them, knows really well that the fake ratio is just horribly massive. It's a total joke. Granted, in some product segments, you mostly get good stuff, but in some others, such as alu elcaps, discrete semiconductors like power FETs, LEDs, etc.,  you get basically over 90% fakes (or otherwise unusable or severely out-of-spec stuff).

On average, is it 5%, 20%, 50% or 70% crap, I don't know, but it doesn't matter; the ratio is too big anyway, so that anyone who has tried it too many times, has stopped buying the Ebay parts; except when they know what they are doing, or simply have to take the risk.

Back to the EEVblog forum tradition; threads like this show up all the time, and it's always people telling you not to buy the Ebay parts - which is a great general advice for any beginner - and then we see blueskull defending the market. I understand very well that he's irritated due to the more or less hidden rasistic undertones people too often show.

I like doing business with the Chinese, and I don't like the "everything Chinese is a scam or super shitty quality" mentality, which is plainly wrong.

But this is something we should and can evaluate based on facts, not feelings. The ratio of bad stuff sold by Chinese Ebay sellers is just huge. This is a fact that everybody can confirm on their own. I have bought a lot of stuff and know very well my defect percentage is somewhere around 30-50%. Today, it's a lot less, since I only buy Ebay stuff I think I can trust on, such as pin headers. But buying the Ebay components cannot be recommended for a beginner, nor when it comes to a safety-critical component. X2 capacitors wouldn't be on my Ebay list!
« Last Edit: April 22, 2017, 02:34:34 AM by Siwastaja »
 

Offline RukyCon

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Re: [First post] Fake x2 capacitors?
« Reply #30 on: April 22, 2017, 03:11:08 AM »
What if i only plan on using them on custom projects? [Like small LED lights]
 

Offline james_s

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Re: [First post] Fake x2 capacitors?
« Reply #31 on: April 22, 2017, 03:14:37 AM »
Yeah I'd like to make it clear that when I complain about "Chinese sellers" I'm not complaining about the general population of China, nor am I implying that everyone in China selling stuff on ebay is a scammer, but there are a LOT of scammers selling junk on ebay so the problem is that you don't really know, and it seems the Chinese government is either unwilling or unable to do much about it. I suppose it's a natural consequence of having a red hot market, massive quantities of surplus components, and large numbers of people trying to scrape by and make ends meet one way or another, with a huge pool of buyers way off in a distant land so there is no direct interaction, one can't inspect the goods prior to purchase, and returning defective goods is not cost effective. It's an environment that is ripe for scams.

Now as for buying parts on ebay, some of it is good, some of it is junk, if you know what you're getting or don't mind taking a risk then there are some deals to be found, but buyer beware. There are things I'll buy from unknown offshore sellers and there are things I won't. Safety components like X2 capacitors and high voltage fuses are one of those things I won't. It's just not worth the risk.
 

Offline Siwastaja

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Re: [First post] Fake x2 capacitors?
« Reply #32 on: April 22, 2017, 03:23:04 AM »
Probability theory excercise: Buy 20 components for a project. At 30% fault rate for each component, what is the probability that at least one in the project is faulty? If you spend, on average, 10 hours of debugging caused by each faulty component, how many hours (expected value) are you going to spend on this 20-component project?

My experience on my own projects as well as debugging a lot of others' projects is that while it often works to buy an Arduino board, an LED and a resistor from Ebay to blink the LED, when the project gets any more complex than that, the chances that at least one vital component is broken in a funny way asymptotically reaches 100%. For example, it takes some debugging to find out why a 3V3 regulator is giving out 1V8. As a beginner, you always doubt your own work, which is correct because, when using genuine components, you are the source of 99.9% of the problems. But when you mix in a bagfull of faulty components you need to debug and swap, working for hours and hours on them just to find that they were faulty to begin with, then order some more, wait for a week to get the new parts - which again may be broken - you are creating an environment where you'll never get your project finished until you lose all your motivation.

Another issue is that you typically cannot source all of the components needed in a project from Ebay, so you "need" to buy from a proper distributor anyway.

Ebay is great for sourcing some trivial parts that for some weird reason are missing from the distributors, are hard to find, or are prohibitively expensive for what they are. For example, I have bought several $1 flux pens when FARNELL was, at the time, only selling flux pens for $100/ea(!).
« Last Edit: April 22, 2017, 03:28:44 AM by Siwastaja »
 

Offline wraper

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Re: [First post] Fake x2 capacitors?
« Reply #33 on: April 22, 2017, 03:47:45 AM »
Ebay is great for sourcing some trivial parts that for some weird reason are missing from the distributors, are hard to find, or are prohibitively expensive for what they are. For example, I have bought several $1 flux pens when FARNELL was, at the time, only selling flux pens for $100/ea(!).
I guess you are talking about Bonkote Bonpen. First of all, they are not $100 each but $100 for a pack of 5 which is standard packaging. But you can find places which will open the pack and sell them individually. Secondly those sold on ebay for cheap are all crappy counterfeits, are not ESD safe and don't perform anywhere nearly as well as genuine stuff (tried that crap for comparison).
 

Offline Seekonk

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Re: [First post] Fake x2 capacitors?
« Reply #34 on: April 22, 2017, 03:49:14 AM »
I don't really think of X2 caps as "safety" application. If something is line powered there is always a potential for things to short hence the need for some interruption.  If you buy a polyester X2 cap, then whats the point. After common mode inductors they often go to standard capacitors.  And there are no standard capacitors, they are all designed for particular applications.  X2 caps are at least some implication that they are designed to operate without corona degradation.   I've designed many 480V line powered devices with capacitive dropping and brought them through UL without X2 caps. The caps were designed to withstand AC.  Unfortunately most data sheets for capacitors are including less and less information.  Hard to figure out what the limits of some capacitors are. If you buy a lot of capacitors you get access to engineering dept and they will even design capacitors for you. I've always found these calls fascinating.
 

Offline RukyCon

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Re: [First post] Fake x2 capacitors?
« Reply #35 on: April 22, 2017, 03:55:58 AM »
I do test the parts before soldering the onto the board.

I even test the parts i get from mouser and digi-key.
 
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Offline Siwastaja

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Re: [First post] Fake x2 capacitors?
« Reply #36 on: April 22, 2017, 04:03:05 AM »
I do test the parts before soldering the onto the board.

I even test the parts i get from mouser and digi-key.

The issue is not within completely nonfunctional parts, they are easiest to identify.

Parts that are "tested OK", but misbehave or have reliability issues can end up being horrible wastes of time, and hard to debug in actual full circuit. And these are surprisingly common.

Proper testing takes a lot of time and equiptment, too, if you try to characterize the components.
 

Offline Siwastaja

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Re: [First post] Fake x2 capacitors?
« Reply #37 on: April 22, 2017, 04:07:32 AM »
Secondly those sold on ebay for cheap are all crappy counterfeits, are not ESD safe and don't perform anywhere nearly as well as genuine stuff (tried that crap for comparison).

Flux pens I have bought from Ebay for $1 are certainly not counterfeits since they don't claim any other brand than their own, thus, they are genuine. They don't even try to look like the Bonpens, or any other brand name thing. Indeed, I'm sure these are not ESD safe, but these do work fairly well.

Sometimes, getting a workable but lower quality option for 1/100th the price of the good alternative is a good choice. This principle doesn't, however, work with most Ebay components, since they are usually priced at near distributor prices, and the parts can cause countless hours of debugging, something that cannot be described simply as "lower quality".
« Last Edit: April 22, 2017, 04:11:13 AM by Siwastaja »
 

Offline wraper

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Re: [First post] Fake x2 capacitors?
« Reply #38 on: April 22, 2017, 04:13:43 AM »
They don't even try to look like the Bonpens, or any other brand name thing. Indeed, I'm sure these are not ESD safe, but these do work fairly well.
well, basically if you search for flux pen on ebay, basically there are 2 things. Fake bonpens and other type which is like marker. Those are much worse than a brush. And similar (but much better quality) flux pens don't cost nearly as much as bonpen even at digikey.
 

Offline RukyCon

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Re: [First post] Fake x2 capacitors?
« Reply #39 on: April 22, 2017, 04:34:09 AM »
I do test the parts before soldering the onto the board.

I even test the parts i get from mouser and digi-key.

The issue is not within completely nonfunctional parts, they are easiest to identify.

Parts that are "tested OK", but misbehave or have reliability issues can end up being horrible wastes of time, and hard to debug in actual full circuit. And these are surprisingly common.

Proper testing takes a lot of time and equiptment, too, if you try to characterize the components.
Now if i'm going to use them for something like a capacitor dropper supply, wouldn't be easier to diagnose the problem?
 

Offline james_s

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Re: [First post] Fake x2 capacitors?
« Reply #40 on: April 22, 2017, 04:35:01 AM »
X2 capacitors are classified as safety devices, they may be connected directly across the line. If they fail, they must fail gracefully and not catch fire or sit there and smolder. If you want to take the risk, I'm not going to stop you, but I don't think I personally would.
 

Offline Siwastaja

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Re: [First post] Fake x2 capacitors?
« Reply #41 on: April 22, 2017, 04:35:50 AM »
And similar (but much better quality) flux pens don't cost nearly as much as bonpen even at digikey.

... if you can find them. In that case, Farnell couldn't deliver any flux pen under $100, and Farnell was our preferred distributor.

It's very well possible that Farnell had the actual flux pens I was looking for miscategorized or mislabeled. This frequently happens with them. I could have called their support phone. It's a hassle.

Nowadays, due to too many utter fails, I tend to refuse to use Farnell and prefer Digikey instead mostly due to their usable website.

Anyways, my point was that sometimes due to some really silly reason it is impossible to get trivial things from the distributors. Often it's a catalogue mistake, leading to spending a full working hour just to find the part number for a trivial low-cost plastic or metal part. These working hours do have a cost. Inability to get a flux pen under $100 at a certain time was a personal example, maybe not the best possible.
 

Offline Siwastaja

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Re: [First post] Fake x2 capacitors?
« Reply #42 on: April 22, 2017, 04:37:57 AM »
Now if i'm going to use them for something like a capacitor dropper supply, wouldn't be easier to diagnose the problem?

Yeah, in a capacitor dropper it's more about the chances of it catching fire later on, than debugging some issue initially.
 

Offline RukyCon

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Re: [First post] Fake x2 capacitors?
« Reply #43 on: April 22, 2017, 04:44:10 AM »
Can a fuse possibly reduce the chance of that happening?
 

Offline Siwastaja

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Re: [First post] Fake x2 capacitors?
« Reply #44 on: April 22, 2017, 04:47:46 AM »
Can a fuse possibly reduce the chance of that happening?

Of course it can, but it's not a silver bullet.

Any component not becoming a "full" short, but a resistance instead, can itself become a heater element causing excessive heat, leading to fire. But the fault current might not be enough to trip the fuse. This is a known failure mode with capacitors. The very idea of the X2 capacitor is that it's designed so that this is extremely unlikely.
 

Offline james_s

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Re: [First post] Fake x2 capacitors?
« Reply #45 on: April 22, 2017, 04:53:04 AM »
A fuse is certainly a good idea though, regardless what capacitor you use. Something rated high enough for the voltage, with a current as low as it can be without risking false trips.
 

Offline RukyCon

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Re: [First post] Fake x2 capacitors?
« Reply #46 on: April 22, 2017, 04:58:07 AM »
Can a fuse possibly reduce the chance of that happening?

Of course it can, but it's not a silver bullet.

Any component not becoming a "full" short, but a resistance instead, can itself become a heater element causing excessive heat, leading to fire. But the fault current might not be enough to trip the fuse. This is a known failure mode with capacitors. The very idea of the X2 capacitor is that it's designed so that this is extremely unlikely.

That's why i said reduce, not prevent.

Now, which would you trust more, eBay x2 caps or salvage x2 caps. [EDIT: Forgot the L in salvage so i put it in. :-[ ]
« Last Edit: April 22, 2017, 05:17:09 AM by RukyCon »
 

Offline james_s

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Re: [First post] Fake x2 capacitors?
« Reply #47 on: April 22, 2017, 05:11:24 AM »
Savage? Did you mean salvage?

Personally I would trust salvage more, assuming they are in good condition and came from reputable equipment.
 

Offline RukyCon

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Re: [First post] Fake x2 capacitors?
« Reply #48 on: April 22, 2017, 05:15:10 AM »
Savage? Did you mean salvage?

Personally I would trust salvage more, assuming they are in good condition and came from reputable equipment.

Yes, i did mean salvage, My bad.
 

Offline Fungus

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Re: [First post] Fake x2 capacitors?
« Reply #49 on: April 22, 2017, 10:43:04 PM »
But this is something we should and can evaluate based on facts, not feelings. The ratio of bad stuff sold by Chinese Ebay sellers is just huge.

Yes, but the price of buying "good" stuff is sometimes so high that it's often worth buying two or three lots from different sellers and crossing your fingers.

eg. Here in Spain any order from Farnell et. al. carries a minimum 15 bucks shipping cost.

Stuff like MOSFETs and voltage regulators are almost all rejects/fakes (apparently) but even so it's only a real problem if you're selling them to people or planning to use them at high power ratings. For home/hobby use or powering a toy from a 9V battery you'll be fine with an eBay regulator.

 


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