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INA118UB instrumentation amp woes

Discussion in 'Electronic Repair' started by JW, Jul 26, 2006.

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  1. JW

    JW Guest

    Hello,

    Has anyone seen any lot problems with BB/TI INA118UB instrumentation amps?
    http://focus.ti.com/docs/prod/folders/print/ina118.html

    We've just received 100 of these devices that we use on the front end of a
    A/D and they all appear to be bad. They are marked INA118UB with lot code
    0425. We run them from +5VDC power supply, and regardless of their input,
    their output is pegged at 4.2VDC. It occurred to me that these could be
    forgeries.

    Also, they were purchased from Part Miner and it's beginning to look like
    they may be putting up a fight with regards to our returning them - has
    anyone had problems with this sort of thing with them?

    Thanks.
     
  2. Mr. Wizard

    Mr. Wizard Guest

    You pose a good point about knock off chips. I'll keep that one in
    mind whenever I purchase parts through part miner.

    Is this a new circuit you are using the IAMP in? I'm sure you ruled
    out all other possibilities before coming to the conclusion that it is
    indeed the instrument amp.

    Please, post how it goes. I'm interested in knowing if the part houses
    are passing along forgeries.

    cheers
     
  3. Send one or two to TI - I'm sure they'll be able to tell you pretty quickly.
     
  4. Kingcosmos

    Kingcosmos Guest

    TI's authorized distributors are Arrow, Avnet, Mouser, Digikey, and
    Newark. I would first ask where Part Miner aquired these because there
    is an issue with counterfeit parts in the industry...or so I hear.
     
  5. JW

    JW Guest

    Nope. We just built 500 boards - 400 worked or had other issues,
    The other 100 have bad amps. All the working boards have a different lot
    code. The two sets of lots were purchased from different vendors.
    I will, thanks.
     
  6. JW

    JW Guest

    Good point, I'll see if I can contact someone there...

    Thanks to all for your followups.
     
  7. JW

    JW Guest

    Well, it looks like they're forgeries. This is from the support engineer
    at TI, after I supplied them with a picture of the markings on the chip:

    "I would say that the parts were not manufactured by Texas Instruments. We
    acquired Burr Brown in 2001 and the top side markings *if* correct would
    imply a date in 2004. The top side marking standard would have been
    switched over to TI's 5 or 7 digit date code rather than 4 at a year and
    definitely by 2004.

    It is possible that Part Miner procured the INA118's from our authorized
    distributors but they will have to be able to show the paper work to prove
    that they acquired them from such authorized channels. We can guarantee
    how the parts are stored and shipped when they are sold by our authorized
    distributors: Arrow, Avnet, Mouser, Digikey, and Newark; however, when
    parts are obtained on the grey market then all bets are off."

    Another reason not to use unauthorized suppliers, and to stay away from
    Part Miner.
     
  8. Mr. Wizard

    Mr. Wizard Guest

    Thank you for posting a follow-up. If Part Miner is unwilling to
    verify their sources then they will definitely go on my no buy list.
     
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