Zener Diode Identification

Discussion in 'Electronic Repair' started by Choong, Jul 18, 2007.

  1. Choong

    Choong Guest

    Hi everyone, I am repairing an industrial PSU and there is a few glass
    types zener diode on board and I found one which is shorted but the
    problem with these small glass type zener is that it is only marked with
    the numeric "123" and nothing more than that so how do I know what is
    the zener voltage of this diode?

    Thanks
    Choong
    Choong, Jul 18, 2007
    #1
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  2. Choong

    Eeyore Guest

    Choong wrote:

    > Hi everyone, I am repairing an industrial PSU and there is a few glass
    > types zener diode on board and I found one which is shorted but the
    > problem with these small glass type zener is that it is only marked with
    > the numeric "123" and nothing more than that so how do I know what is
    > the zener voltage of this diode?


    It sounds like you need the schematic. "123" is inadequate to identify the part.
    Is that really the only marking ? Have you got a picture ?

    Graham
    Eeyore, Jul 18, 2007
    #2
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  3. Choong

    Meat Plow Guest

    On Wed, 18 Jul 2007 17:49:14 +0800, Choong wrote:

    > Hi everyone, I am repairing an industrial PSU and there is a few glass
    > types zener diode on board and I found one which is shorted but the
    > problem with these small glass type zener is that it is only marked with
    > the numeric "123" and nothing more than that so how do I know what is
    > the zener voltage of this diode?
    >


    Zeners are usually marked 5V1 (5.1 volts) 12V (obvious) 5.1.
    123 doesn't ring a bell for me. Take a magnifying glass and a bright light
    and have another look. Also, are the other zeners marked the same way? And
    how did you determine they are zeners?
    Meat Plow, Jul 18, 2007
    #3
  4. Some context on the application is needed if you can't find a schematic or
    parts list. Zeners are usually used for either protection or as a
    reference. What is it connected to?

    Leonard

    "Choong" <> wrote in message
    news:469de17f$...
    > Hi everyone, I am repairing an industrial PSU and there is a few glass
    > types zener diode on board and I found one which is shorted but the
    > problem with these small glass type zener is that it is only marked with
    > the numeric "123" and nothing more than that so how do I know what is the
    > zener voltage of this diode?
    >
    > Thanks
    > Choong
    Leonard Caillouet, Jul 18, 2007
    #4
  5. Choong

    AJ Guest

    Are the other associated diodes all marked with the same identification? If
    so connect one of them to a circuit using a variable voltage and current
    limiting resistor. Ramping the voltage up and montioring it across the
    diode, it will be obvious when you reach the zener voltage, start low then
    bring the voltage up gradually.
    Examine the circuit for electrolytic caps near the diodes, this may indicate
    roughly what voltage range the diodes may be. As Leonard posted, some of
    these are used for protection, as a crowbar device.
    "Leonard Caillouet" <> wrote in message
    news:CJpni.502$...
    > Some context on the application is needed if you can't find a schematic or
    > parts list. Zeners are usually used for either protection or as a
    > reference. What is it connected to?
    >
    > Leonard
    >
    > "Choong" <> wrote in message
    > news:469de17f$...
    >> Hi everyone, I am repairing an industrial PSU and there is a few glass
    >> types zener diode on board and I found one which is shorted but the
    >> problem with these small glass type zener is that it is only marked with
    >> the numeric "123" and nothing more than that so how do I know what is the
    >> zener voltage of this diode?
    >>
    >> Thanks
    >> Choong

    >
    >
    AJ, Jul 18, 2007
    #5
  6. Choong

    Franc Zabkar Guest

    On Wed, 18 Jul 2007 17:49:14 +0800, Choong <> put
    finger to keyboard and composed:

    >Hi everyone, I am repairing an industrial PSU and there is a few glass
    >types zener diode on board and I found one which is shorted but the
    >problem with these small glass type zener is that it is only marked with
    >the numeric "123" and nothing more than that so how do I know what is
    >the zener voltage of this diode?
    >
    >Thanks
    >Choong


    Could it be 12B ???

    If so, then "B" probably indicates the tolerance.

    - Franc Zabkar
    --
    Please remove one 'i' from my address when replying by email.
    Franc Zabkar, Jul 18, 2007
    #6
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