EBAY fakes again?

Hi all, a rather puzzling ebay story: I make small boards with small SRAM modules 8Kx8. Sometimes, ebay auctions are too good with respect to digikey's and other distributor prices. So I took the chance (I can return the obvious fakes most of the times). Chips are marked UT6264CSC-70LL, so I downloaded the datasheet for them that floats on the internet and ordered a few, since they have the needed specifications for my boards (at least on the datasheet). Once they arrive, I solder a couple in place, and sure enough, they hang the data bus firmly. After some troubleshooting, turns out that the CE2 on pin 26 is actually not connected (I use both CEs), there're not even the protection diodes to the rails that I could measure, looks NC like pin 1. All the rest is good, they are indeed 8kx8 chips, with correct low power standby and all I could test looks right. Now, I tried to contact the seller with no answers back. My question is: how likely is the datasheet is actually wrong on the CE2 part? I know there're 8Kx8 SRAMs without the CE2 input, but why one would bother to mark them as fakes? I think I'm going anyway leave at least a neutral feedback due to the seller disappearing when I notified a problem. But I would surely leave a negative if I can be sure that the part numbers don't meet the datasheet. Any clue (yes, I'm not going to buy electronic parts off ebay anymore)? Frank

Reply to
frank
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FWIW salvaged parts are big business in China and can suffer such damage. If I bought nonfunctioning goods and seller disappeared I wouldn't be leaving neutral feedback :)

NT

Reply to
tabbypurr

good points, these could be bonding errors and got discarded (though it's strange that I've got only pin 26 missing.) I think negative is getting more likely than neutral.

Frank

Reply to
frank

+1. If there were a "wronger than wrong" button, I'd push it.
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Tim Wescott 
Wescott Design Services 
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Reply to
Tim Wescott

Confirmation bias? It would be fully fraudulent to sell products that won't work at all, but maybe if just one pin is missing, some applications would be okay.

I'd still be suspicious of read/write errors, and perhaps bit pattern errors (not that SRAM should be susceptible to row hammer, but similar things can apply).

Tim

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Seven Transistor Labs, LLC 
Electrical Engineering Consultation and Contract Design 
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Reply to
Tim Williams

yes, that was my original concern, explaining why they are not what they are supposed to be requires some datasheet "understanding" capabilities. I'm not sure I want to embark in claiming the chips are fake. But I left a negative feedback for not answering.

I only soldered two of them, and I couldn't identify any problem once I worked around the single /CE issue. My programs could identify single bit errors in some modules in other occasions, so these two looks good so far. I agree however that I shouldn't trust them probably.

Frank

Reply to
frank

There's not much difference to the seller between neutral and negative feedback. Most users only look at the percentage which is only positives. You have to click on the rating to see what is behind it.

Does this guy have more than a couple of sells? I was buying obvious fake SD cards to see how much it was a problem for the sellers to deal with the negative feedback. Many of them were kicked off eBay before the purchase was complete. Others shipped product that was a smaller chip than it was tagged for. You had to run a memory test to tell it wasn't a full size card, a $3 card sold for $15-$30. Some of them would reply to a complaint that the factory was to blame and they were victims too.

Nearly all of them would disappear and show up with a new seller name. They do something to rack up sales, I think there are services to do that. They "pay" for goods and the seller "ships", but there is money under the table to pay the buyer to do the bogus purchases. I expect it is similar for chips.

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Rick C
Reply to
rickman

I have that experience as well, but I don't believe it because anyone in the business of selling memory cards should know about this scam and should make sure their source delivers them actually working goods, especially when at a low price.

So I put the blame on them and request my money back or I will complain at Aliexpress where I place my orders.

Reply to
Rob

They may not be "fake" but floor sweepings. That is, parts that failed final test, in your case perhaps with a bond wire missing. They may have come from the dumpster behind the fab. ;-)

Reply to
krw

yes that's what I thougth too, but they seem reliable when driving only the /CE. If the CE2 was not bonded out, it would probably behave like an open input and work randomly. I ordered replacement chips from digikey, shipping is 2/3 of the total cost :(

However, I've just got a full refund. The seller asked if I can retire the feedback, but I haven't been able to find a way to change the feedback. It must be a well hidden feature.

Frank

Reply to
frank

Not necessarily. I wouldn't leave an input float in production but many such circuits have a weak pull up/down. Gates, not so much.

Not so much different than anything else. How much did the bogus chips cost you?

Did he refund your time, too?

Reply to
krw

I recently left an open input on a cmos chip (forgot to solder it) and it really had a kind of random behaviour. It was also an SRAM chip by the way.

same as on digikey but including shipping costs. However now I have the bad chips for free (fwiw).

good point, not really :( Time is not so expensive if living in south Italy anyway, and the lesson learned is good too.

Frank

Reply to
frank

An enable?

Time isn't free.

Yeah, don't buy parts from persons unknown.

Reply to
krw

Yeah. I prefer known part scavengers.

NT

Reply to
tabbypurr

I prefer factory originals from known supply chains but if you like wasting valuable time on bogus parts, well, there is a reason these people are still in business.

Reply to
krw

A friend told me of a problem with a CMOS RAM circuit board a long time ago. It was flaky so that they could not figure out what the symptoms meant. Eventually they found the chips had no Vdd connection. They were being powered by the current flow through the inputs!

I believe the vendors should take responsibility for their merchandise. I believe many of these vendors sell bad devices knowingly and rely on only a fraction asking for refunds to make their profit. I believe you should let the bad rating stand.

I had an opportunity to buy some FPGAs at half the price I would pay otherwise. The vendor was 4 Star, one of the bigger non-mainstream distributors. My fab house wouldn't be responsible if the parts failed, so I didn't want to take the risk even though I think it was a small risk.

Funny part is the only place you can buy these parts with a pedigree is Arrow. They have 72,878 and the part is EOL. They originally wanted a somewhat reasonable price according to the web site and I have bought some couple of thousand at those prices. I asked for a quote on a larger quantity than they gave me a higher price than the web prices at lower quantities. Good thing I didn't buy them. Just after that, I found that my customer is discontinuing the product lines this board goes into. I would have been stuck with some thousands of parts.

I've been tracking what the web page shows since June and it looks

*very* much like I am the only buyer of these parts. They may be holding them for a longgggg time.
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Rick C
Reply to
rickman

I don't think Aliexpress has the same sort of feedback rating system that eBay does. So I am leery of buying much from them. I know most vendors are *very* wary of bad ratings on eBay. They will bend over backwards to fix problems... usually.

I bought a USB programming cable for Lattice devices from eBay when I could have gotten it cheaper on Aliexpress. But I've never gotten a warm fuzzy from them as I can't find much on their procedures for handling problems. Maybe I shouldn't worry so much. I pay with a credit card and I can always dispute it through them.

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Rick C
Reply to
rickman

My experience with Aliexpress is very good. A couple of times when I went for the cheapest seller I got my order cancelled by Aliexpress and my money refunded without doing anything. They apparently cancel orders when they get a number of complaints about a seller.

They do have a feedback system. And when something is wrong you can open a dispute. This is easiest when you have not yet confirmed you received the goods in working order: the payment is held by Aliexpress until you confirm delivery (or some specified timeout, which you can extend when you have not received it but expect that it is delayed in the mail).

Once you confirmed delivery there is nothing formal that Aliexpress will do, but apparently the sellers are afraid ending up in the first category so they refund money on their own.

So, preferably test your goods not only visually and superficially. I found that my 64GB SD card was an 8GB fake only after having confirmed delivery. Tested it with the wellknown tool later.

Reply to
Rob

I was being somewhat humorous, partly because I/we have used lots of recycl ed parts. That's why recyclers are in business, it's a workable business mo del. It goes on on a large scale in the 3rd world. BUT I would never buy IC s that way, and would not build $1,000 products with them.

A percentage of the products you buy in stores or online are built with sca venged parts. And no, it's not why they fail. Tr, D etc have proved reliabl e. Cs are ok if lytics are properly tested, which depends on your source. R s I don't see any point in. ICs are another matter, and I see a regular dri bble of threads on here reminding me why not to use them.

Most of you folks are in areas where competition isn't too tight, and make expensive products. In low cost stuff it's a different matter.

NT

Reply to
tabbypurr

Was wondering about the seriousness but didn't see a smiley, either.

I used recycled parts when I was a kid. Not since. If it even comes out of the bin and sits on the bench and isn't used, it's discarded. $1000 "product" is about all I touch. That's only a day's work. Time is too valuable to screw around with.

Cs are an issue. Counterfeits aren't uncommon. As you say, there is no point in reusing Rs, and ICs are too easily damaged to even think about reusing, particularly in a product. Of course, if you don't mind shipping defective products, use 'em and don't bother testing, either.

If it's so cheap that quality doesn't matter, perhaps. Otherwise, time is too expensive to mess with them.

Reply to
krw

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