Junk Transistors

Discussion in 'General Electronics Chat' started by Wendy, Dec 21, 2008.

  1. Wendy

    Thread Starter Moderator

    Mar 24, 2008
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    A short while ago I was running some experiments on some PN2222A transistors, which in theory are equivalent to 2N2222A's. I got some anomolous results, so I went to something else instead. I just broke out my meter and measured some hfe's, and got 3, 9 and 2 respectively. Guess these were someones fallouts.

    Wierd part is, for basic stuff like transistor invertors I guess I can use them, just being aware where they came from.
     
  2. hgmjr

    Moderator

    Jan 28, 2005
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    Bill,

    That hfe value sound very low indeed. One thing you will need to look out for is that some manufacturers used different pinouts than others on their transistors. If you can tell who manufactured the transistors you may want to track down the actual mfr's datasheet just to make sure that you have the pinouts correct.

    hgmjr
     
  3. Wendy

    Thread Starter Moderator

    Mar 24, 2008
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    I tried every combo, that and these suckers worked in a circuit. The picture in the data sheet matches exactly, and how many parts are made in India? The date stamp on the package of 100 of these devices was Aug 13, 1990.

    The only reason I posted is I thought is was funny, that and I figure there is something in if for some of the newbies.
     
  4. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    With collector and emitter swapped, reverse beta will generally be in the single-digit range that you measured, but the new C-B junction (actually E-B) will break down when "Vce" is greater than about 7V.
     
  5. Wendy

    Thread Starter Moderator

    Mar 24, 2008
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    They measured zero on the DVM swapped. I think these really are that bad, barely able to be qualified as transistors.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    Bill,
    Try replacing the battery in your meter.
     
  7. theamber

    Active Member

    Jun 13, 2008
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    Multimeter error most likely.
     
  8. Audioguru

    New Member

    Dec 20, 2007
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    I betcha the lousy transistors were purchased at RadioShack.
    That is one of the reasons (the other reason is that their high prices were a rip-off) why they are gone from Canada.
     
  9. Wendy

    Thread Starter Moderator

    Mar 24, 2008
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    Nope, and I used more than one meter, one meter couldn't even see them. The meters were then verified using good transistors (not to mention they have low battery indicators).

    Radio Shack is innocent in this case. Matter of fact, their 15 pack of NPNs and another of PNPs came up quite good, with a beta of 247 give or take.

    These really were that bad, it happens. I've never bought counterfit or junk components before, even Radio Shack on a bad day can do better. They were part of a lot of a thousand I spent $10 on. Overall I still did OK on the deal.

    Anyone want some cheap transistors? :D
     
  10. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
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    Not to get all practial on y'all, but......in all my born days (and I have a LOT of 'em, by the way) as an electronic tech, I've NEVER encountered a transistor that couldn't be evaluated with a VOM or a DVM in the DIODE mode. We learned all about curve tracers and all that in school, all of which we threw out the window once we got in the real world. If a transistor junction conducts on direction and not the other, it's good.

    Let the pie toss begin. :)

    eric
     
  11. Wendy

    Thread Starter Moderator

    Mar 24, 2008
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    Want some transistors? Their cheap! Let me know what you do with them...
     
  12. theamber

    Active Member

    Jun 13, 2008
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    Are you saying that you have 100 NPN transistors you bought from some supplier and they are all defective?
    Why don't you return them? Can we know where did you buy them?
    The only logical explanation to this is that some crook has got batches of rejects or defective transistors from the garbage and is selling them. The thing is that during the manufacturing process only few out of millions are defective. They only test a few out of every batch. I mean those type of transistors are mostly use by hobbyists what kind of low scam will do something like that?. You should definitely find out where they came from.
     
  13. Wendy

    Thread Starter Moderator

    Mar 24, 2008
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    When you buy surplus from flea markets you takes your chances. Its the nature of the game. Most times you win, sometimes you loose. I doubt the guy who sold me knew they were bad, the package was sealed and these are OLD. Besides, I have 900 others left (each package a different type) that will console me.
     
  14. SgtWookie

    Expert

    Jul 17, 2007
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    Well, you could have purchased 500 Fairchild PN2222's from Mouser for about the same cost - except shipping - and I'll bet your reject rate would be a heck of a lot lower.

    I wouldn't be surprised to find that the transistors you purchased were rejects from automated testing during "pick and place" assembly of PCB's.
     
  15. theamber

    Active Member

    Jun 13, 2008
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    Yes that make sense but even the guy at the flea market should return your money I mean I understand some may be defective but not all. You should ask for your money back next time you see this guy. Most of the stuff in electronics flea markets are left overs anyways. But as the Sarge said if they cost the same from a reasonable supplier I mean was the point of buying in the flea market and taking chances. Definitely you should tell the seller about this. I prefer to buy from Digikey semiconductors.
     
  16. leftyretro

    Active Member

    Nov 25, 2008
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    Well some of us enjoy looking for and buying bargain components and equipment from electronic flea markets, surplus outlets and of course E-bay bargains. I consider it my own form of recycling, good for the earth. I recall buying a pack of 100 2N3904 and 100 2N3906 transistors for like a dollar a pack somewhere and so far they have all worked. Things like relays and switches are available at such lower costs then new retail and I would say that 95% of the parts I've bought that way are new old stock and have never been used.

    I never pay anywhere near retail prices for the things I buy at those places and my "parts bin" would cost X10 or more to replace at retail. That's not to say that I really needed or will ever use up all my parts but that's what makes it a hobby and not a vocation. ;)

    Lefty
     
  17. theamber

    Active Member

    Jun 13, 2008
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    Nothing wrong with recycling I used to go to the TRW swap meat on Redondo Beach South LA years ago. The way I see it is like this:
    I never buy any equipment 'as is' if I don't have a way to test it, I assume is broken, I pay accordingly. About semiconductors I just don't trust flea markets. I mean you have enough variants in electronics only to add more from 'new' semiconductors that suppose to work fine.
     
  18. eblc1388

    Senior Member

    Nov 28, 2008
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    Nothing wrong with recycling, why not take it a step further. :mad:

    Here is how one can recycle those capacitors with very short legs.

    [​IMG]
     
  19. Wendy

    Thread Starter Moderator

    Mar 24, 2008
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    I wonder how much money someone spend ripping people off. Some people spend more time coming up with ways to cheat people than trying to earn an honest living.
     
  20. eblc1388

    Senior Member

    Nov 28, 2008
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    Here is some more.

    [​IMG]
    [​IMG]
    [​IMG]They will work, albeit for just a little while and then die a horrible death. :mad:
    [​IMG]
     
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