sjep120r100 faking from China

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well I had some fake 2SC5200/2SA1943 which I put in a higher current super regulator to run at +/60, had +/-70V in and they failed open under load in a matter of seconds. replaced them thinking it was something I did, checked everything, replaced a few caps, reduced the Vout and Vin for a lower +/-35 with +/-42 in.... burned again
 
My question will be selling "janeh2100" and "sharpseller2000" two vendors but the same person on Ebay (China).

Or they do not even know what they are selling, or will also be swindled by the mafias of transistors ....


My question:


------------
Dear janeh2100,

What is the value of IDSs fet. This is fet Original? Are you sure that this is not fake fet?

The letter J does not have the dash above ...

Ensure that it is original I buy 10, but if they do not Idss between 6mA and 12mA and transconductance of approximately 20mS, I will have to return them.

respects

---------------------------------

hello client,
to be honest, I'm not professional about this transaction, cannot 100% sure if it's original
my supplier just informed me it's J-FET, NOS Transistor, New, and in good working condition guarantee.
hope you can make sure before purchase
best regards,
Ari

E-mail : moonmai555@yahoo.com.cn
Phone Number: 086-755-25506967
working date: 9:00AM - 18:00PM , From Monday to Saturday
 
well I had some fake 2SC5200/2SA1943 which I put in a higher current super regulator to run at +/60, had +/-70V in and they failed open under load in a matter of seconds. replaced them thinking it was something I did, checked everything, replaced a few caps, reduced the Vout and Vin for a lower +/-35 with +/-42 in.... burned again
The bjts were destined to fuse. In hind sight, what will you do today different to ensure the avalanche of damage past will never occur?
 
I had oscillation problems on a part that otherwise tested ok using minimal initial testing. This was in direct comparison to known good parts. After inquiring further, I eventually ended up getting the manufacturer to check box and batch numbers. They were unable to correlate the info on the parts with their production records. I was a couple days from court. Seller finally refunded the transaction.
 
Consider the possiblity of a part that is close in operation being rebranded as another, more attractive part. Functional, but not true to specs of desired parts. On some levels, it may test close normal specs. Many people would never go beyond this and accept any problems that occur as something else. I got lucky as well as having some good guidance from some friends
 
I had oscillation problems on a part that otherwise tested ok using minimal initial testing. This was in direct comparison to known good parts. After inquiring further, I eventually ended up getting the manufacturer to check box and batch numbers. They were unable to correlate the info on the parts with their production records. I was a couple days from court. Seller finally refunded the transaction.

Thanks buzzforb. You have several important steps in a great process to deal with fakes.
  • Put the part in test circuit.
  • It misbehaved
  • Talked to the manufacturer of authentic parts
  • It compared fake with authentic
  • Got an iron clad proof of a misfit part
  • Confronted the seller with this evidence
  • Recovered money from seller
 
Ha. You make it sound so easy.
Your difficult and unpleasant experience is an important lesson to us. You practiced a logical and successful approach to managing fakes, and beat the culprit at its game. Unfortunately, the seller was collateral damage. I would aspire to do what you did when faced with a similar situation. Why be cheated and feel bad [or helpless] about doing nothing about it?
 
For solid state, I pretty much buy only from a reputable source such as Digikey. Buying cheap parts online fuels the fake-part industry.
I fully agree with you. You'll be in a position to return the misbehaving part for a replacement or a refund.

Here's an excerpt from a brochure by THRESHOLD Corp. for its Model S/150 Series II power amplifier. I am going back to the early 1980's and quote the extensive testing it did to qualify semiconductors. "To assure reliable operation, even under severe conditions, each power semiconductor of the S/150 [bjt] is tested to its secondary breakdown point at 125 volts before being placed in parts inventory". Also, from another Technical Brochure; "Every transistor undergoes individual testing and characterization, as necessary, for transconductance, matching, noise, saturation, and voltage breakdown prior to entering parts inventory."

In another publication, Mr. Pass emphasized the importance of the reverse-biased Collector to Base breakdown voltage. I do not have the exact language for it. Threshold prevented "off-spec" from its inventory.

Collectively, we can generate a general Quality Control procedure to qualify semiconductors for DIY use. I believe the first step is :
  • Buy from a reputable source as Bigun said above
  • Reputable or not, push it through key electrical tests for confidence building.
Let's generate such tests [in addition to flg's] to qualify the hot one SJEP120R100.
 
The bjts were destined to fuse. In hind sight, what will you do today different to ensure the avalanche of damage past will never occur?

I dont know what you mean? I followed the BOM and super regulators are high dropout regulators, I used them within recommended operating conditions and they failed because they were Fakes and not the part they were supposed to be, which is a 150W 230V part.

they should have been operating well within their SOA.

what I will do to avoid it next time is to not buy anything ever again from dodgy EBAY sellers, or buy any transistor from ebay unless recommended by someone I know who has experience with the seller and the exact part.
 
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I dont know what you mean? I followed the BOM and super regulators are high dropout regulators, I used them within recommended operating conditions and they failed because they were Fakes and not the part they were supposed to be, which is a 150W 230V part.

they should have been operating well within their SOA.

what I will do to avoid it next time is to not buy anything ever again from dodgy EBAY sellers, or buy any transistor from ebay unless recommended by someone I know who has experience with the seller and the exact part.
qusp: I agree with you. The bjts were Fakes, and thus their fate was already preset to fail.
 
dont go by just the lettering differences. The original R100's and some R100As used the more 'white' letter printing. They also used a more 'shiny' legs and drain substrate backing.

That being said, I've had a couple of parts searchers seek these out lately. They are saying any offer right now are from seedy sources and likely fake. So really buyer beware.
The IC district of China can unfortuntely produce whatever you want for a part in printing in a couple of days notice.

R100's of any sort will have a much lower VgS test then any IRF240.

Tea Bag is right, the "hard to read" lettering is not by itself an indication of anything. SemiSouth used a couple of Asian packaging firms. I have both types of package markings in my inventory, all of which was walked out of the SemiSouth building in Starkville, Mississippi by me. No fakes in my inventory. :)

I have neither seen nor tested a fake, but I don't think the counterfeiters are trying to put a device inside the package that is intended to survive scrutiny. My guess is they just wanted to shovel something out the door during the first buying frenzy. In that case, it should be rather easy to tell a genuine SemiSouth enhancement mode JFET from any likely fake. The forward current of the gate source diode (or the gate drain diode) will look like a pn diode. And then the rather high transconductance of the R100 or equivalents is easy to spot beginning around Vgs = 1 V. No MOSFET will duplicate both terminal characteristics.

Over the past two weeks I have tested literally hundreds of these parts as I sorted through my inventory that I acquired from a 12 year relationship with the company beginning at the beginning. I will post a few curve tracer images in the next couple of days that will illustrate what the real thing looks like if you have access to a decent quality curve tracer. As for genuine inventory, it is all in the hands of former customers supporting their own products or "hoarders." I can assure you that the company's inventory shelves are now bare and production is firmly stopped. SemiSouth had its own fab. No other fab anywhere in the world made SemiSouth JFETs. I had access to the inventory room during the last couple of months as the company unwound operations. They sold off the sell-able inventory quickly to raise cash, as you might imagine.

I have to thank all of you as a community (DIY Audio) for discovering the unique properties of SemiSouth JFETs in high-end Class A audio amps, and Nelson Pass in particular for giving the discovery a voice. The founders of the company were all thinking power switching because that is our professional background. Jeff Casady developed SiC SITs for radar at Northrop Grumman before joining me in starting SemiSouth. We never thought about linear as a motivation for SemiSouth's products. You all just made it happen.

I've enjoyed reading all about it. In my power electronics class this Spring semester at Mississippi State University, a Pass F2J amp is going to be one of our early analysis assignments. Cool stuff like this they will love!

Regards,

Mike Mazzola
 
first of all I feel safe in expressing a hearty thanks from all of us fanatics here at DIY to Mike Mazzola for providing his first hand knowledge.
One of the great things about DIYAudio is that the real great contributors to the art are willing to share knowledge and experience freely here.

As one who stood on the sidelines and have not obtained a single SIC device, where does that leave those who are looking.
Are the devices from CREE at all suitable?
 
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Here's an excerpt from a brochure by THRESHOLD Corp. for its Model S/150 Series II power amplifier. I am going back to the early 1980's and quote the extensive testing it did to qualify semiconductors. "To assure reliable operation, even under severe conditions, each power semiconductor of the S/150 [bjt] is tested to its secondary breakdown point at 125 volts before being placed in parts inventory". Also, from another Technical Brochure; "Every transistor undergoes individual testing and characterization, as necessary, for transconductance, matching, noise, saturation, and voltage breakdown prior to entering parts inventory."

Here's a story for you. We were buying BJT output devices from a major semi
manufacturer (you can guess who, but they no longer make transistors and
it was forty years ago). We paid a premium to have all devices tested for
secondary breakdown as we had seen some problems with that, and we also
tested them in-house. We found a significant percentage breaking down
at voltages way below spec, so clearly they were either not testing them or
shipping them anyway. We called in the factory rep who was a real d**k
and after much discussion they agreed to replace them. We shipped the
bad parts back.

Later we received a batch of replacements, and found that they had our
felt pen test marks on them.

:cool:
 
Reminds the customer dissatisfied with the steak, complains that is hard and unpalatable, the waiter takes the steak to the the kitchen, and the cook strip the wooden clogs and gives you the steak with enough force, sends redeliver the same steak the client. And the customer says, "will now good, is too soft."

He had not felt pen to mark the steak!
 
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