I'm starting a new thread devoted to sharing experience with questions related to genuine and counterfeit parts.
I'm reserve this first post to help build navigation in the thread to various posts by adding links to the start of various discussions.
I'm sure this is a "repeat" of many other threads on the topic, so feel free to link to other posts/threads on the forum.
I'm reserve this first post to help build navigation in the thread to various posts by adding links to the start of various discussions.
I'm sure this is a "repeat" of many other threads on the topic, so feel free to link to other posts/threads on the forum.
I understand your candor @WhiteDragon in that you're implying there's a lot of folks with subjective opinions and I understand that. The hope is we can make this thread more about objective approaches. The goal here is to share knowledge and experience on how to avoid buying counterfeits in the first place, and identifying them if the former didn't occur in time.
The first relevant post here is regarding determining if parts acquired are Genuine Harris IRFP9140's, or fakes/counterfeits. Below are some images and basic measurements. The date code from '96 to '97 still falls within when Harris was a company prior to being bought by Interstil, but it sure is a clearly different approach to markings from one year to the next. Additionally, the "MALAY" marking is different on the "press" marking indicating a different fabrication line.
I'm curious if anyone can confirm that the laser engraved version here has any chance of being legit. I realize Vgs can vary, so is there any way to clearly know if a part is fake via measurement? I'm willing to give various circuits and measurements a try.
Images below taken from a stereo-microscope and hence the color difference from above.
The first relevant post here is regarding determining if parts acquired are Genuine Harris IRFP9140's, or fakes/counterfeits. Below are some images and basic measurements. The date code from '96 to '97 still falls within when Harris was a company prior to being bought by Interstil, but it sure is a clearly different approach to markings from one year to the next. Additionally, the "MALAY" marking is different on the "press" marking indicating a different fabrication line.
I'm curious if anyone can confirm that the laser engraved version here has any chance of being legit. I realize Vgs can vary, so is there any way to clearly know if a part is fake via measurement? I'm willing to give various circuits and measurements a try.
Images below taken from a stereo-microscope and hence the color difference from above.
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Be interesting to see where this thread goes, sort of 
. My experience is, I've been buying "cheap" semi's online for over 20 years. Not one fake. Bin ends, seconds, faulty, out of spec - yes. Fakes? No. I think the whole fake semi's thing is completely exaggerated. Sure some long extinct expensive semi's are ripe for the picking but some here say they receive fake transistors that are worth literally cents and in current production, or that ON Semi is fake etc. etc.
. My experience is, I've been buying "cheap" semi's online for over 20 years. Not one fake. Bin ends, seconds, faulty, out of spec - yes. Fakes? No. I think the whole fake semi's thing is completely exaggerated. Sure some long extinct expensive semi's are ripe for the picking but some here say they receive fake transistors that are worth literally cents and in current production, or that ON Semi is fake etc. etc.
You had to be lucky enough. Today even fake microcontrollers or specialized ICs are common.
By measuring transcoductance over several frequency points. Method is described in the attached article at page 5. Transconductance should remain almost the same. International Rectifier’s IRFP9140 has a gradual drop starting from 200 Hz and shelving at 1 kHz.
There is another markings and logo version of the genuine Harris IRFP9140, probably produced after 1998, when company logo was changed to slanted letters. I’ve just measured them using mentioned article and Gm doesn’t change over frequency. Input capacitance and threshold Vgs also conform to datasheet specifications.
Quite possibly. I think too buying transistors as opposed to rare uP's helps. Ironically the last purchase I made were IRFP 140's / 9140's. Genuine IR's but the 140's had very low VGS on whereas the 9140's were normal. Be fine for a regulator but not a PP amp as intended. They were 1/4 the price from Mouser so I took my chances... and lost.
Here's another example of what are very likely counterfeit transistors from eBay. A seller (Polida 2008) who has had reputable business with others on this site providing the same exact parts I ordered (FQA36P15) sent me what are clearly sanded down counterfeits. They did a good job sanding the part down to avoid obvious grain striations from the sanding process, however, the parts show clearly that they were sanded down by the inconsistent pattern in the injection mold pockets (some pockets are visible, others have been sanded away). They are laser engraved labels and do not represent what is shown on the picture for the parts. I did some basic Vgs measurements, and they fall within spec at 3.5-4.0V, however, I suspect a more detailed measurement would show them to be fakes.
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I plan to just buy some of the IXTQ36N30P parts from Mouser as a path forward. I just wanted to share my experience so others can learn as Polida 2008 has provided genuine parts of this exact part number to others on this forum in the recent past, which led me to feel confident I would possibly also receive genuine parts. I have plenty of genuine FQA28N15 from reputable sources (Rochester & Arrow), so it's a bummer I can't find the complimentary P-type FQA36P15 anywhere.
@birdbox
Publishing this is so very appreciated. Although I don’t order large sized transistors from ebay, I do order the smaller JFETS from punkydawgs but we all know he is a genuine seller and is actually in the pro industry designing electronics.
Regardless, the learning process here is important so we can detect fakes from other sources. I will stick with Mouser/Digikey for now and of course trusted sources and like minded diy’ers (like you!) for the future.
The other problem I see here is that these fake transistors are making it into someone’s product whether diy or small commercial which means reliability and longevity are obvious concerns.
Best,
Anand.
Publishing this is so very appreciated. Although I don’t order large sized transistors from ebay, I do order the smaller JFETS from punkydawgs but we all know he is a genuine seller and is actually in the pro industry designing electronics.
Regardless, the learning process here is important so we can detect fakes from other sources. I will stick with Mouser/Digikey for now and of course trusted sources and like minded diy’ers (like you!) for the future.
The other problem I see here is that these fake transistors are making it into someone’s product whether diy or small commercial which means reliability and longevity are obvious concerns.
Best,
Anand.
BB,
If Polida still pushes for you to pay for shipping open a case with eBay and/or Paypal and fight back.
Polida tried the bait and switch pricing tactic with me for a DAC chip. Purchased at the listed price, a few days later received a message saying they were out of stock but they can get them from another "Distributor" for 4 times the price. Not very fond of Polida's business model.
I got burned a while back with an Aliexpress purchase where there is basically no consumer protection.
If Polida still pushes for you to pay for shipping open a case with eBay and/or Paypal and fight back.
Polida tried the bait and switch pricing tactic with me for a DAC chip. Purchased at the listed price, a few days later received a message saying they were out of stock but they can get them from another "Distributor" for 4 times the price. Not very fond of Polida's business model.
I got burned a while back with an Aliexpress purchase where there is basically no consumer protection.
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