Watch out for fake 74LS logic ICs.

[Fflint]

I've heard a lot about fake opamps and other cheap ICs, but I never heard about fake 74LS logic ICs. I need specifically LS (or HCT) for compatibility with ancient devices and I recently bought some "cheap" SN74LS02N from a local ebay clone. When they arrived I noticed straight away the ti logo is fake, but I checked them in my Tl866II and it reported fine.

Then once I tried to use them in a device with a 1mhz clock none out of 10 worked. I then got another two of the same chips, but from a reputable seller. Both of those work fine.

Here is a photo of one chip from the reputable seller on top, and the fake one on the bottom.


The seller returned my money and he wants the chips back tomorrow so there isn't much testing I can do, but I might just hook it up to a signal generator and an oscilloscope to seed what is it exactly about them that makes them fail.

The supply chain situation for those chips must really be dire for people to resort to faking them. I now need 74LS133 which I can only get from China and I wonder if there is any chance of it being real...

[james_s]

It's prudent to just never buy stuff like that on ebay. It may be ok for tinkering around on a breadboard but you can't trust the specs and really, why not just buy from a reputable seller like Digikey? They are still fairly inexpensive and much more likely to be real genuine parts that meed the published specs.

[Fflint]

It's prudent to just never buy stuff like that on ebay. It may be ok for tinkering around on a breadboard but you can't trust the specs and really, why not just buy from a reputable seller like Digikey? They are still fairly inexpensive and much more likely to be real genuine parts that meed the published specs.

You're right, but if only it was that easy (to always be able to buy from digikey or equivalents).

What I do is hobby related and sometimes I do small runs of 5~10 units for sale too so this affects how I buy parts.

Here(in my part of EU) we have 3 large distributors Digikey, Mouser and Farnell. Out of those 3 only Farnell has a local warehouse. Shipping is still expensive, but cheaper than the remaining two. Other than those 3 we also have lots of little family run shops that often have been in business for decades. They are usually quite reputable. Finally there are various auction and local ads sites (like ebay/Craigslist).

The cost of shipping for those little shops is usually very cheap, double that for Farnell, double that again for Mouser, and double it for the third time for Digikey. Most of my order values are around what it costs to ship with digikey, but that is not the only issue with large distributors. These days it is very difficult to get all parts at one distributor. So imagine having to order with all 3.

Also, the kind of older parts I often buy (74LS,STM32,Atmega etc) are sometimes found on local ad sites sold by individuals.

So long story short, if you're making commercial projects and you have multi $k budget it is indeed prudent to only buy from big distributors. For small scale buyers... We sometimes have to take chances.

Here is an update about those counterfeit chips as I've spent some time on a breadboard testing them and comparing with a genuine thing (bought in a local fairly reputable shop). Interestingly they can be made to work even at rather high speeds, but they have a much stronger tendency to self oscillate and the propagation delay is about 3 times the genuine thing.

I used a breadboard as everyone knows those things are not ideal for signal integrity, but still there are lots of different behaviours between those two chips so let's list them. C is counterfeit, G is genuine

1.
C - Applying power to both chips with all inputs and outputs pulled down with 12k to ground (no decoupling cap) makes the chip oscillate immediately on two out of its 4 gates. The noise of this oscillations is present even on outputs of two gates that don't oscillate (at 1V).
G - No oscillations

2. 100nF ceramic decoupling cap added across power right next to chip.
C - no difference
G - no difference

3. Outputs of all gates have been switched from resistor pull downs to pull up(same 12k) to be in line with nand truth table.
C - Self oscillations gone
G - no difference

4. Propagation delay measured.
C - Approx 38nS
G -Approx 12nS (still worse than datasheets value of 9)

5. Square ttl signal was applied to one of each gate's inputs. Frequency was varied from 10kHz to 40Mhz.
C - works fine until it starts drawing a lot more current at about 15MHz, 50mA PSU current limit cuts off power at around 23MHz
G - Works fine all the way. Power consumption slightly rises from "0" to 3mA near 20MHz,Output amplitude drops slightly above 30MHz. I can't say if this is a chips fault or the breadboard wiring (likely the latter).

6. Sine wave applied same frequency range (10k to 40MHz).
C - Same effect as with square wave above 15MHz,below however the shape of the output signal looks "better" than the genuine thing? Strange.
G - Fine all the way, but at mid frequencies of 1MHz the shape of the output looks a little strange. When it switches high it reaches well above threshold (about 4V),then slowly raises to 5V. The counterfeit chip went straight to 5V (when it worked).

So here we have it. I suspect those are not even TI chips (on account of the propagation delay being so much higher), but some other make. Perhaps they are rejects from manufacturing that failed self oscillation/crosstalk tests. Do logic manufacturers do such tests? I have no idea.

[wraper]

Here(in my part of EU) we have 3 large distributors Digikey, Mouser and Farnell.

You have TME in Poland with <$4 delivery within your country.

[wraper]

I now need 74LS133 which I can only get from China and I wonder if there is any chance of it being real...

https://www.tme.eu/en/katalog/?search=74LS133&s_field=1000011&s_order=desc

[wraper]

Also you have Maritex in Poland, https://www.maritex.com.pl/ which can be more cost effective for common components and allows to buy cheap components at lower quantity. For example you can buy a single resistor for less than a cent https://en.maritex.com.pl/passive_components/resistors/smt_resistors/chip_resistors_0603/resistors_0603_-_5/rmc0603-100k-h.html

[Doctorandus_P]

Then once I tried to use them in a device with a 1mhz clock none out of 10 worked.

Geez, if they don't even work at a milli Hz that must be real bad. I wonder how slow your Tl866II must be if it still is not able to flag this as an error.

[Stray Electron]

 FWIW  I've never seen US made ICs that look like those. US made parts have a smooth slick finish but these have a pebble finish and they look like they may have been sand blasted to remove the original markings.

  That said, there are so many counterfeit electronic parts on the market today that I would not trust ANY part unless I bought it directly from a very reputable source such as Digikey.

[CaptDon]

Yes doctor, I am sure we knew he meant Mhz but used mhz. And actually at 1mhz (Millihertz) they would probably transition through a linear range and self oscillate or do stupid things unless the 'one millihertz' clock still had a nice rise time.

[Kleinstein]

The supply current going up is a bit strange. Chance are the fake could be some slow (e.g. 74C02) version, maybe the 74L02 or 7400 - though I would not expect the high current consumption.

For an 74LS02 there is really no need to resort to a dubious source like ebay. It may sometimes be OK for more excotic parts / old parts that are NOS, though with a risk.

There are few more smaller resellers that have at least the more standard parts.

[Bud]

When you consider all the troubles you had and time spent on testing, shipping charges from reputable distributors becomes a non-issue.

[Tomorokoshi]

FWIW  I've never seen US made ICs that look like those. US made parts have a smooth slick finish but these have a pebble finish and they look like they may have been sand blasted to remove the original markings.

  That said, there are so many counterfeit electronic parts on the market today that I would not trust ANY part unless I bought it directly from a very reputable source such as Digikey.

The counterfeit part appears to be "blacktopped", which is where a black coating is applied over an original part, and new markings are applied.

They counterfeit ceramic capacitors. Anything that gets into the electronic waste stream can be processed and appear in the counterfeit supply chain.

[free_electron]

22 arss 8 ... should have marked it arse ...

[Fflint]

I now need 74LS133 which I can only get from China and I wonder if there is any chance of it being real...

https://www.tme.eu/en/katalog/?search=74LS133&s_field=1000011&s_order=desc

Cool, thanks for this. I never knew :-)

Also you have Maritex in Poland, https://www.maritex.com.pl/ which can be more cost effective for common components and allows to buy cheap components at lower quantity. For example you can buy a single resistor for less than a cent https://en.maritex.com.pl/passive_components/resistors/smt_resistors/chip_resistors_0603/resistors_0603_-_5/rmc0603-100k-h.html

I saved this one too.

[Fflint]

When you consider all the troubles you had and time spent on testing, shipping charges from reputable distributors becomes a non-issue.

My intention here is not to defend use of counterfeit parts, but if electronics is your hobby,  not a paid job, and you know your way around measuring equipment as well as you already have one or two known good chips of the type you're buying I see no harm buying cheap parts and trying to find bargains. Especially when the site you're buying on has reasonable buyer protection. So as long as you're aware you might get burned there is no harm buying on all those sites. However, not everyone can tolerate issues that might crop up, and not everyone wants to spend half a day testing counterfeit chips out of curiosity, so I understand where you're coming from.

Over all the years I've been buying electronic parts I've probably made no more than 5 orders to big suppliers. Everything else was bought through local ebay-clone-like sites, Aliexpress and ebay itself. This is the first time I actually got counterfeit parts and amongst my purchases before were such things as $120 a pop RF power transistors from Aliexpress, nice OCXOs, rf power resistors etc. (all expensive stuff I ever buy through such sites is from sellers with recent good feedback and prices that aren't "too good to be true").

As for this experience I just would like to say it wasn't really much trouble for me(mainly because I had known good ICs from another source to check).It was quite interesting and educational. That's why I posted this thread. I was surprised such cheap ICs are being counterfeited in a fairly sophisticated way.

For those interested in the details. Those chips were sold as "tested good" and I paid $3.4 (plus $2 local shipping) for 10 of them. When I contacted the seller with a complaint he didn't ask me to test them, he just wanted to know exactly what was wrong, once I explained he refunded me including shipping. He just asked I post them back in an economy letter (about $1.5). So one could say I'm loosing that buck and a half, but I agreed because technically he described them as "tested good" not "original TI" and they do test OK so I don't mind posting them back.

For comparison's sake I already bought genuine TI SN74LS02N in a local physical store for $12.5 for 10. I'll definitely be ordering those 74ls133 from TME.

[Stray Electron]

    I agree 100% with Bud on this.  When I need to order parts, I usually need them for a repair or for a project that I'm working on and don't want to have waste time testing and troubleshooting the parts and possibly having to redo the repair. So I want GOOD parts to start with.

   If I want to test or play around with parts of unknown quality then I yank some off of one of the old circuit boards that I have laying around.

[Geoff-AU]

Either you consider your free time to be priceless or worthless, it seems.

I also have no time for figuring out how to make counterfeits work for me.  I don't want to buy counterfeits, EVER, because I don't want to support that "industry" in any way.  All it does it make it harder to make nice things.

[james_s]

The only counterfeit parts I buy are the Maxim LED display drivers, the real ones are ridiculously expensive and the Chinese parts have always worked perfectly for my purposes.

[Fflint]

    I agree 100% with Bud on this.  When I need to order parts, I usually need them for a repair or for a project that I'm working on and don't want to have waste time testing and troubleshooting the parts and possibly having to redo the repair. So I want GOOD parts to start with.

   If I want to test or play around with parts of unknown quality then I yank some off of one of the old circuit boards that I have laying around.

Those 5 times I ordered parts from large distributors were all for repairs. So I do agree with that.

Either you consider your free time to be priceless or worthless, it seems.

I also have no time for figuring out how to make counterfeits work for me.  I don't want to buy counterfeits, EVER, because I don't want to support that "industry" in any way.  All it does it make it harder to make nice things.

Fair enough. I suspect no one wants to "spend time making counterfeit parts work for them". At the same time there are plenty of people interested in reverse engineering them, making die photos etc.

I have to admit I was tempted to decap those chips and to make some microscope photos of the dies, but I don't have a good way to decap them. Also based on the limited testing I think these are indeed 74ls02, but not meeting specs probably so nothing that exciting to see there.

[bidrohini]

I never really considered ebay a dependable source for components

[magic]

I think the logo on the upper specimen looks dodgy too...

[Geoff-AU]

Fair enough. I suspect no one wants to "spend time making counterfeit parts work for them". At the same time there are plenty of people interested in reverse engineering them, making die photos etc.

I have a colleague who enjoys the challenge of making things work even though it's faulty.  He understands that everything is junk, the seller knows that it's junk, they are getting a government subsidy for "exporting electronics" (even though it's faulty) and westerners are paying for the privilege of disposing of the junk by reciting the phrase "oh it was only a couple of bucks" while casting it into the bin.  The people who complain about it being junk get offered a refund and that's just the cost of doing business.  100% is junk, 80% of people throw it away without a second thought because they have too much money to care, 20% complain so you give them refunds, and you're still making a healthy income stream from crowdsourcing your e-waste disposal on ebay.

That whole thing gives me the shits though.  I don't like my time being wasted by disingenuous people.

[Fflint]

I think the logo on the upper specimen looks dodgy too...

It does seem so right? But I know for a fact the shop I bought it at is legit and those chips spent 30 years sitting on a shelf there. Before they were bought from a big distributor. Also they test fine up to about ~40MHz and above that I suspect my breadboard and wiring was deteriorating the signals more than anything else. The measured propagation delay was slightly above the datasheet value at 12ns, not 9ns,but I think this is within acceptable tolerances.

The store has been there for many decades. Interestingly when I told the woman working in the stora about the fake chips and how they are testing ok, but self resonate a lot more and have triple the propagation time she said back when they (the store) were buying 74xx chips directly from a local fab (CEMI used to be a Polish fab in distant past) there was an official route to buy them and an unofficial way at much lower prices, but then you got chips with no markings and usually with various faults. They(this store) were always getting official chips and that's one of the reasons they still exist 50 years later.

I was mildly surprised counterfeit chip making wasn't a Chinese invention.

I recently got some 74LS273 from another small local supplier that has good reputation and they look like this :

To me they look a bit weird, but I never had chips made in Portugal before.

Fair enough. I suspect no one wants to "spend time making counterfeit parts work for them". At the same time there are plenty of people interested in reverse engineering them, making die photos etc.

I have a colleague who enjoys the challenge of making things work even though it's faulty.  He understands that everything is junk, the seller knows that it's junk, they are getting a government subsidy for "exporting electronics" (even though it's faulty) and westerners are paying for the privilege of disposing of the junk by reciting the phrase "oh it was only a couple of bucks" while casting it into the bin.  The people who complain about it being junk get offered a refund and that's just the cost of doing business.  100% is junk, 80% of people throw it away without a second thought because they have too much money to care, 20% complain so you give them refunds, and you're still making a healthy income stream from crowdsourcing your e-waste disposal on ebay.

That whole thing gives me the shits though.  I don't like my time being wasted by disingenuous people.

There is a big difference in analysing those things to see how they done it and trying to make dodgy ics work in your device anyway. I tend to draw a line between the first and the second activity. I often buy from potentially dodgy sources, but I always get my money back if I get bad stuff. If everyone did that those guys would go out of business.

The problem however, is that many people who buy such parts don't test them fully, meaning to use them for future projects. Even if they do have a logic IC tester, those testers(that I saw) rarely test parameters. They just test if the chip works.

[tooki]

It's prudent to just never buy stuff like that on ebay. It may be ok for tinkering around on a breadboard but you can't trust the specs and really, why not just buy from a reputable seller like Digikey? They are still fairly inexpensive and much more likely to be real genuine parts that meed the published specs.

You're right, but if only it was that easy (to always be able to buy from digikey or equivalents).

What I do is hobby related and sometimes I do small runs of 5~10 units for sale too so this affects how I buy parts.

Here(in my part of EU) we have 3 large distributors Digikey, Mouser and Farnell. Out of those 3 only Farnell has a local warehouse. Shipping is still expensive, but cheaper than the remaining two. Other than those 3 we also have lots of little family run shops that often have been in business for decades. They are usually quite reputable. Finally there are various auction and local ads sites (like ebay/Craigslist).

Digikey has free shipping to Poland on orders above €50, customs/duty/VAT prepaid. So just keep a list of non-urgent stuff you need, and use items from the list to pad small orders to get to the free shipping threshold! (I mean, one can always get another Arduino or Nucleo board, or some flux, or some tool you’ve been wanting, or just restock standard components you’re running low on.)

[Fflint]

It's prudent to just never buy stuff like that on ebay. It may be ok for tinkering around on a breadboard but you can't trust the specs and really, why not just buy from a reputable seller like Digikey? They are still fairly inexpensive and much more likely to be real genuine parts that meed the published specs.

You're right, but if only it was that easy (to always be able to buy from digikey or equivalents).

What I do is hobby related and sometimes I do small runs of 5~10 units for sale too so this affects how I buy parts.

Here(in my part of EU) we have 3 large distributors Digikey, Mouser and Farnell. Out of those 3 only Farnell has a local warehouse. Shipping is still expensive, but cheaper than the remaining two. Other than those 3 we also have lots of little family run shops that often have been in business for decades. They are usually quite reputable. Finally there are various auction and local ads sites (like ebay/Craigslist).

Digikey has free shipping to Poland on orders above €50, customs/duty/VAT prepaid. So just keep a list of non-urgent stuff you need, and use items from the list to pad small orders to get to the free shipping threshold! (I mean, one can always get another Arduino or Nucleo board, or some flux, or some tool you’ve been wanting, or just restock standard components you’re running low on.)

Thanks, I didn't know.