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Zeners Short Circuit Problem

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by proksima, Aug 25, 2006.

  1. proksima

    proksima New Member

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    Does anybody have a recent problem regarding to THT Zener Diode (especially 9V1 and 5V6) (They behave like short circuits)
    Actually we faced with such a problem where we use 1.3W Zener diodes below their electrical ratings in our capacitive supplies (In our boards our worst case Zener condition is 600mW ).

    We observe this problem in the first function test during manufacturing or in the life test also so the failure rate doesn’t depend on the working period of the electronic board.

    I do appreciated for all kinds of comments.

    Best regards,

    Ahmet
     
  2. RODALCO

    RODALCO Well-Known Member

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    Hi Ahmet,

    Were these zeners connected up correct ?? with the circled line towards the positive ?

    [+] [I<] [ load resistor] [-]

    Were these zeners all from the same batch ?

    Whoever sold you them may have had a bad supplier.

    The 5V6 or 9V1 are common values which are available and should have no particular problems.
    In the opposite mode they conduct at 0.6 Volts.

    Try a 2V7 and 3V0 in series (which gives you 5V7 total )
     
  3. proksima

    proksima New Member

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    Zeners shorts circuit

    Thanks for your reply first,

    Yes, we use our Zeners in a right way(correct polarities, correct usage in a capacitive supply, etc.) and controlled all diode batches for the weekly periods.

    However we can't find the main reason which triggers the Zener diode short circuit problem.
     
  4. dave

    Dave New Member

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  5. audioguru

    audioguru Well-Known Member Most Helpful Member

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    1.3W is probably the absolute max the zener can dissipate in a nice cool room with free ventilation and with very short leads soldered to large-area copper runs on a pcb. Something in the operation of your zeners is different and is causing them to overheat.
     
  6. Roff

    Roff Well-Known Member

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    Can you post a partial schematic?
     
  7. hjames

    hjames New Member

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  8. Roff

    Roff Well-Known Member

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