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fake mosfet!

Discussion in 'Electronic Repair' started by [email protected], Apr 2, 2007.

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  1. Guest

    Hello group,

    I am repairing a failed JRL-2000F HF linear amplifier. It employs 48
    mosfet (2SK408 and 2SK409). The symptom was power unit shutting down
    because it detected a short circuit in the amplifier boards. I knew
    all mosfet had been previously replaced.
    I started disassembling the power amplifier boards looking for the
    short (which looked like a diode drop on a multimeter, from positive
    to negative only). I first removed all heatsink to exclude any short
    on the tabs to ground. Nothing, the "short" was still there... then I
    tried to power a board with a 60A power supply, thinking that the
    failing component would release its smoke, well, no smoke at all,
    fortunately not even from my poor power supply.
    Then I removed one of the mosfets and I checked it off circuit and
    noticed I could measure a diode drop from drain to source, right, I
    checked on the datasheet and they're supposed to have this diode....
    WAIT! what direction is this diode? Yes, you guessed, the diode was in
    the WRONG way. What I have is a lot of FAKE 2SK408 and 2SK409. Looking
    at the datasheet, pinout for the 2SK408 is G-S-D and for the 2SK409 is
    D-S-G, the fake ones have all G-D-S pinout, no matter if they have the
    K408 or K409 marking, all have the hitachi logo printed on the case,
    they look indeed the right thing and they're indeed a kind of a
    mosfet, I could open the channel with a few VGS volts.
    Did anyone ever heard of fake components? Unfortunately I don't know
    where the owner of the amplifier got the replacement "new" mosfets.

    Regards

    Francesco IZ8DWF
     
  2. Faked parts are not uncommon, take a look here:

    http://sound.westhost.com/counterfeit.htm

    Jorgen
    dj0ud
     
  3. Jeroni Paul

    Jeroni Paul Guest

    Some brands offer versions with another terminal ordering and another
    letter suffixed on the part number. Did you try to wire it correctly?
     
  4. michaelchina

    michaelchina Guest

    hi, dear freind, i would like to know if you still need 2SK408 and
    2SK409,we have stock to offer,

    this item(2sk409 2sk 408) is very absence in the market,and i think
    perhpaps some lawless seller to make fake to sell.

    last year ,we have a customer in AR. they also got fake 2sk409 2sk408
    in their locate market, so i am not surprised what your happend.

    we have especialized in electronic over 19years.most of our customers
    of china distribute repairs line and graduate school ,we also have
    plenty of overseas customers,pls find our reference in enlosed
    documents.
    because we have many years experience for repairs line,so we can
    convince you of our service,we hope to establish long-term trade
    relationships with you.
    since 2001,we became a member of ERAI.

    pls give me e-mail if you need any component, sepeciately
    stop-producted,hand-find,

    e-mail:

    MY msn: skype : michaelvisual

    huandong electronics ltd.







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  5. Guest

    Brand of the fake is indeed Hitachi as the original one, also it's
    very difficult to wire "correctly" 48 mosfets if the original pcb and
    heatsink are drilled for the standard pinout reported on the only
    datasheet I've been able to find; plus it doesn't mention any
    alternative pinout. I believe these mosfet are now obsolete but since
    they have been used in some expensive equipment there're always outlaw
    manufacturer that just produce cheap fakes as it wouldn't be very
    profitable to make real clones. I really doubt Hitachi would allow the
    use of a type code (and its logo too) if the manufacturer doesn't
    follow the original specs of the part.

    regards

    Francesco IZ8DWF
     
  6. Eeyore

    Eeyore Guest

    Counterfeit components are rife these days.

    Buy your parts from a manufacturer authorised supplier.

    Graham
     
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