Announcement

Collapse
No announcement yet.

Diode mode testing of motherboards question

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    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.

    #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


      #3
      Re: Diode mode testing of motherboards question

      Watch this video:

      https://youtu.be/pRpyHF2dfq0

      Comment


        #4
        Re: Diode mode testing of motherboards question

        Originally posted by mon2 View Post
        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
        9 PC LCD Monitor
        6 LCD Flat Screen TV
        30 Desk Top Switching Power Supply
        10 Battery Charger Switching Power Supply for Power Tool
        6 18v Lithium Battery Power Boards for Tool Battery Packs
        1 XBox 360 Switching Power Supply and M Board
        25 Servo Drives 220/460 3 Phase
        6 De-soldering Station Switching Power Supply 1 Power Supply
        1 Dell Mother Board
        15 Computer Power Supply
        1 HP Printer Supply & Control Board * lighting finished it *


        These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

        1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
        2 Hem Saw Computer Stack Board

        All of these had CAPs POOF
        All of the mosfet that are taken out by bad caps

        Comment

        Working...
        X