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Trying to trace source of non-working op-amps

Discussion in 'Embedded' started by Anton Erasmus, Oct 9, 2003.

  1. Hi,

    We bought some TL074 op-amps a while ago. We have built up over a
    100 boards, and we now find that the TL074 devices are not working at
    all. If we replace the device with a genuine TI TL074 device, or any
    other OpAmp the board works as required. The non-working TL074 devices
    has a "FAT" F as the logo. Are there any sites where one can search
    for a manufacturer based on the logo they put on their devices ?

    Regards
    Anton Erasmus
     
    Anton Erasmus, Oct 9, 2003
    #1
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  2. Anton Erasmus

    Richard Guest

    A quick google search on "electronics manufacturers logo" yields the
    following as the 4th link.

    http://www.chipdocs.com/logos/logotypes.html

    Only "F" I see there is Fairchild Semiconductors, which was my first guess
    anyway.

    HTH
     
    Richard, Oct 9, 2003
    #2
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  3. Anton Erasmus

    Guy Macon Guest

    When the opamp is "not working at all" what voltage do you see at
    the plus input, the minus input and the output? If you put the
    opamp in a test circuit, does it work (in other words are they only
    bad when installed on your board or always bad)?
     
    Guy Macon, Oct 10, 2003
    #3
  4. Lewin A.R.W. Edwards, Oct 10, 2003
    #4
  5. Hi Anton,
    Is this device in a very tiny surface-mount package, with abbreviated
    package markings? Are you sure that the chips you bought before are
    actually TL074s?

    Listed vendors for the TL074 are:

    ST Microelectronics
    Motorola Semiconductor Products
    ON Semiconductor
    Texas Instruments

    also:

    National Semiconductor (M38510/11906BCA, military version)

    None of those has a logo that looks like an "F"...
     
    Lewin A.R.W. Edwards, Oct 10, 2003
    #5
  6. Hi,

    Thanks for the response. I could also only find Fairchild with an F
    logo. I was hoping for some site with maybe more obscure manufacturers
    logos. The component suppliers here in South Africa sometimes buy from
    extremely odd places for "standard" components. (74 series, Op-Amps,
    4000 series etc.) Sometimes these companies have logos that on first
    glance are quite similar to the main stream semiconductor logos.
    Unfortunately even though we specificially specify the more main
    stream seimconductor part numbers, it sometimes happen that the buyers
    get told by the suppliers that the component is an exact equivalent at
    a 10th of the price, and they cannot resist.
    Most of the time this is not a problem, but if these devices are
    really from Fairchild Semiconductors (a company from I do not expect
    or suspect of supplying dofgy devices), then I need to find out the
    problem.

    Regards
    Anton Erasmus
     
    Anton Erasmus, Oct 11, 2003
    #6
  7. Hi,

    The circuit is a stock standard non-inverting amplifier with a gain of
    about 20. This particular board has been manufactured in batches of
    100 every 3 months or so for the last 10 years. We have had problems
    with dodgy TL074s once before, but then the components came from
    some obscure semiconductor house in India. With the non-inverting
    Amp isolated from the rest of the circuit, then one basically get
    nothing out no matter what the input is. The chips seems completely
    "dead". Replacing the chip with a TL074 from TI, or with any other
    quad op-amp we had lying around, then the circuit works as expected.
    We have had ICs from obscure semiconductor houses in the past, who's
    logos at first glance looks very much like the "Big" semiconductor
    houses. The dodgy TL074s logos looks like Fairchild Semicondcutor's.
    I have never experienced or even heard of Fairchild's devices working
    other than as specified. If I can establish from where these devices
    came, then I can at least try and ensure that we do not buy from that
    supplier again.

    Regards
    Anton Erasmus
     
    Anton Erasmus, Oct 11, 2003
    #7
  8. Anton Erasmus

    dmmilne Guest

    Component subsitution is becoming a problem, particularly with common garden
    variety parts, and suppliers who aren't authorised dealers. They may be
    manufacturered by dodgy component makers who may have a very basic semiconductor
    manufacturing facility set up, or the components may be castoffs from the major
    semi manufacturers that didn't come up to spec at various testing stages and were
    stolen/sold off to experimenters/whoever. They may even be legitimate cheaper components
    that have had their correct markings removed, and markings of a more expensive
    component substituted.

    Some examples of fake components have been power transistors that were used in audio
    amplifier kits here in Australia. These had markings that at first glance indicated
    that they were made in Mexico, but when you looked closer, it actually said "MEX1CO",
    ie. substituting a "1" where an "I" should have been. When the amplifier was first
    turned on/cranked up, the output transistors destroyed themselves. The owner usually
    went back to the shop where they bought the kit, and purchased replacement transistors.
    More often than not, accidently purchasing more fakes, until the the method of identification
    was found.

    Fake pentium cpus have been getting around for years.
    http://www.heise.de/ct/english/97/01/018/

    The only way to be assured of purchasing genuine components is to deal ONLY with the
    manufacturer, or it's legitimate representatives.

    --

    Regards
    David

    =================================
    Reply to

    dmmilne at ozemail dot com dot au
     
    dmmilne, Oct 22, 2003
    #8
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