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nets on the motherboard

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    #1

    nets on the motherboard

    I am a big noob but eager to learn so.. please help me to understand how DC electricity in laptop motherboard works and all through the nets... so, there are many nets on the motherboard...for example basic are gnd-ground, nv-negative, pv-positive....
    And, off course when i plug the charger in, the DC electricity is going from positive part in charger to all chips and other parts in motherboard, powering them up, and coming back to charger through negative and ground? making the whole circle? off course, on its way mosfets, diods, resistors... are changing voltage, resistence to supply each chip, card, memory modul, cpu with voltage needed to work. Is this correct?
    Further, when charger is not plugged there is no connectivity or should i say continuity in the whole motherboard, because there is no closed circle. But, if i use multimeter i will see that lets say ground and negative are connected, and they shouldnt be in any way connected to any other net? positive or other? cause that would mean that there is short somewhere? further, should all other nets have no continuity also? lets say net +5vs and +5v_kbled? should they have continuity if charger not plugged?
    Please answers/advices, links to books/pdf on the theme very appriciated
    Last edited by myth77; 03-21-2017, 09:09 AM.
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    #2
    Re: nets on the motherboard

    DC voltage isn't "connected" to all chips, dc input goes to many power supplies, some of them will be ON all time (mostly 3.3V and 5V) and some will be OFF when laptop is OFF but with power (S5 status), you shouldn't have continuity to ground on any rail (be careful, big BGA chips will fool your meter and might show a "short").

    In most cases all 5V nets "come" from the same power supply, but the power of the net could be controlled by a mosfet or transistor and after that point the power has a different name, thus a new NET.

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      #3
      Re: nets on the motherboard

      Originally posted by cpt.charlie View Post
      DC voltage isn't "connected" to all chips, dc input goes to many power supplies, some of them will be ON all time (mostly 3.3V and 5V) and some will be OFF when laptop is OFF but with power (S5 status), you shouldn't have continuity to ground on any rail (be careful, big BGA chips will fool your meter and might show a "short").
      my mistake, bed english...i meant goes to many power supplies

      Originally posted by cpt.charlie View Post
      In most cases all 5V nets "come" from the same power supply, but the power of the net could be controlled by a mosfet or transistor and after that point the power has a different name, thus a new NET.
      ok, thx, but when power is down, should i have continuity between those new nets and 5v net or it depends? if depends, on what it depends? Or i will figure it with expirience?

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        #4
        Re: nets on the motherboard

        This guy has some well explained videos
        https://www.youtube.com/channel/UCXb...AKbUKImRX-HBHg

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          #5
          Re: nets on the motherboard

          Originally posted by myth77 View Post
          ok, thx, but when power is down, should i have continuity between those new nets and 5v net or it depends? if depends, on what it depends? Or i will figure it with expirience?
          Just read the schematic and you will discover if it shiold have continuity or not.

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