Diode mode testing of motherboards question

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  • Scruit
    Member
    • Apr 2022
    • 12
    • USA

    #1

    Diode mode testing of motherboards question

    (I am self-taught in electronics over 20 years as a hobbyist, but I lack some of the fundamentals that folks who went to school for this would know... so please bear with me as I get deeper into this new hobby of retro computing...)

    I'm familiar with diode mode in that it produces a small voltage between the leads and displays the the amount of voltage drop when the leads are connected... however....

    Why do the board repair folks always put the positive lead to board ground and use the negative lead to probe the board itself? My intuition would be to put the negative lead to ground.

    Is the voltage being produced at the negative lead, and the positive lead is then measuring voltage that makes it to "ground"?

    If the testing voltage is being created at the positive lead then I would expect diodes to stop any current flowing in the "wrong" direction.
  • stj
    Great Sage 齊天大聖
    • Dec 2009
    • 30910
    • Albion

    #2
    Re: Diode mode testing of motherboards question

    logic chips have diodes in the input pins connected in reverse to block static electricity - you can check for those going bad.
    i dont see the pint though - most faults are deeper in the chips.

    another reason could be to get a reading faster than in resistance mode.

    Comment

    • mon2
      Badcaps Legend
      • Dec 2019
      • 13829
      • Canada

      #3
      Re: Diode mode testing of motherboards question

      Watch this video:

      https://youtu.be/pRpyHF2dfq0

      Comment

      • sam_sam_sam
        Badcaps Legend
        • Jul 2011
        • 6018
        • USA

        #4
        Re: Diode mode testing of motherboards question

        Originally posted by mon2
        That video was very informative however a little bit long winded but I learn a lot about troubleshoot using that method if you have two identical devices

        Which I never heard of troubleshoot using that method

        Thank for sharing it

        Comment

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