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Old Zener Diode

Discussion in 'General Electronics Discussion' started by magnetec, Apr 19, 2012.

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  1. magnetec

    magnetec

    2
    0
    Apr 19, 2012
    Hi All

    I hope I am in the right forum.

    How would I find the voltage rating of an obscure and obsolete zener diode called the OAX247. Any help would be appreciated.

    Magnetec
     
  2. davenn

    davenn Moderator

    13,671
    1,892
    Sep 5, 2009
    hi there
    welcome to the forums :)

    only a couple of obscure listing on google huh

    if you actually have a working one you would be able to test it

    [​IMG]

    if you have a variable PSU and preferably one that is current limited, you could try the above and starting at a low voltage, say 1V, slowly increase the voltage and observe the reading on the voltmeter. You should see where the voltage gets limited and doesnt rise any more

    Dave
     

    Attached Files:

  3. alfa88

    alfa88

    329
    4
    Dec 1, 2010
    Here's my pictorial to add to Davenn's explanation. I just sorted out a bunch of zeners last week this way. Remember to label the diode if it's going into the parts bin.
     

    Attached Files:

    Last edited: Apr 19, 2012
  4. timothy48342

    timothy48342

    218
    1
    Nov 28, 2011
    What is this part of your pictorial? (What does it do? Whay is it there?)
    [​IMG]
    -t
     
  5. alfa88

    alfa88

    329
    4
    Dec 1, 2010
    Jumper cable
     
  6. davenn

    davenn Moderator

    13,671
    1,892
    Sep 5, 2009
    That really doesnt make sense... tis not the way zeners should be used.
    The whole idea of the resistor is for current limiting to the diode and should be in the positive leg as shown in my diag and the regulated output voltage is taken from the junction of the zener and the resistor

    magnetec, have a look at this site for some zener use with a calculator for the resistor value Zener Diode Voltage Regulator

    cheers
    Dave
     
  7. magnetec

    magnetec

    2
    0
    Apr 19, 2012
    Thanks Davenn

    But the problem is that I don't have one. I have an old circuit diagram that I want to use. The only information not shown is the supply voltage. The only clue would be the data for the OAX247 if I could find it somewhere.
     
  8. alfa88

    alfa88

    329
    4
    Dec 1, 2010
    Whaaa?! I simply have the resistor on the other side of the diode. It's still getting current limited. The measurement is still across the junction of the resistor and diode to the other side of the diode.
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,418
    2,788
    Jan 21, 2010
    I had initially assumed you meant that green twirly bit of wire was somehow connected to the red wire.

    Maybe you didn't mean that.
     
  10. alfa88

    alfa88

    329
    4
    Dec 1, 2010
    Whew! you had me doubting myself.
    Nah, I was just drawing down the way I had my test setup slapped together. The jumper was so I could connect and remove zeners easier. Maybe I'll cleanup the drawing to be more ascetic.
    Magnetec, In lieu of an adjustable power supply you could maybe use a series of cells but it may take quite a few until you get results. Most of the time they're in the range of 4 to 12 Volts but I've had a zener that was 70Volts.
     
  11. davenn

    davenn Moderator

    13,671
    1,892
    Sep 5, 2009
    its just very unorthodox thats all, in the case of a negative rail fault, your zener and assoc circuity would not be current or voltage protected. You should always have the limiting and regulation in the positive rail, showing otherwise could lead those less knowledgeable astray :)

    Dave
     
    Last edited: Apr 20, 2012
  12. alfa88

    alfa88

    329
    4
    Dec 1, 2010
    Tada!:D
     

    Attached Files:

  13. davenn

    davenn Moderator

    13,671
    1,892
    Sep 5, 2009
    hahaha, you're a good lad lol :p
    go to the top of the class and get the gold star :D

    As you have probably seen the difficulties in some threads some members have had trying to explain various electronics principles, it helps if things are done consistantly so as not to confuse the uniniated even further ;)

    like ya drawings very neat!!

    cheers
    Dave
     
  14. ModemHead

    ModemHead

    69
    20
    Dec 2, 2010
    What is a negative rail fault?
     
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