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    #1

    A question about false continuity.

    Here I post a question to which Google has failed me utterly.
    I am currently troubleshooting a motherboard and in the CPU vcore area, ALL of the caps seem to have continuity. And a few others on a certain power rail.
    They all have about 8ohms resistance. Is this a problem or normal?
    My hypothesis is that the caps may be charged on both sides or otherwise meant to pass high mhz ac current from the CPU?
    Please, any help is appreciated. I'm a relative beginner at electronics.
    "The whole problem with the world is that fools and fanatics are always so certain of themselves and wiser people are so full of doubts." -Bertand Russell
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    #2
    Re: A question about false continuity.

    I don't know if 8 ohms is normal or not, but when you measure components in circuit, without desoldering them, you may get false readings if the components are in parallel with other components.

    To get an accurate reading, measure them out of circuit.
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      #3
      Re: A question about false continuity.

      try measuring for longer and also swap probes .
      and also be sure the power is unplugged .
      Last edited by petehall347; 03-18-2017, 12:04 PM.

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        #4
        Re: A question about false continuity.

        It's normal to measure low values if the processor is installed (if you try to measure the VCC rail of a big chip like a processor, PCH or VGA, you will get a low reading)

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          #5
          Re: A question about false continuity.

          To avoid false readings, capacitors are normally removed from the circuit. The best way to test is with a capacitor tester. If you don't have this item, then use an analog meter. The capacitor should slowly charge then reverse the leads and it should kick with that charge then charge in the other direction.

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            #6
            Re: A question about false continuity.

            So based on your feedback, I have another question. The caps that can be found on the underside of a processor socket... are those all connected to the processors 1.5-1.8 volt rail, typically? I thought perhaps some of them were used to pass signal voltage and block power, maybe?

            Also to clear things up, when measuring for continuity ACROSS the caps from the positive side to the negative side (which I assume should just be ground if they are used to keep the power rails steady at load), and getting continuity, as if they were shorted. Than I measured their resistance, and it was 8 ohms, across the cap? This is because of measuring in the circuit? Perhaps because I was feeding the other caps(in parallel, or other loads) with the current form positive multimeter lead and the negative was measuring a lower voltage than it should have thus producing a lower resistance reading?
            "The whole problem with the world is that fools and fanatics are always so certain of themselves and wiser people are so full of doubts." -Bertand Russell

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              #7
              Re: A question about false continuity.

              Like many members said , it's better to test capacitors outside the board . Notice that capacitors work like temporary batteries ; When you test them for continuity , it means they are charged and saturated , with no chance of discharging , giving you different measures , erroneous ones in fact , the next time you test them .

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                #8
                Re: A question about false continuity.

                Originally posted by BangBusDriver View Post
                So based on your feedback, I have another question. The caps that can be found on the underside of a processor socket... are those all connected to the processors 1.5-1.8 volt rail, typically? I thought perhaps some of them were used to pass signal voltage and block power, maybe?

                Also to clear things up, when measuring for continuity ACROSS the caps from the positive side to the negative side (which I assume should just be ground if they are used to keep the power rails steady at load), and getting continuity, as if they were shorted. Than I measured their resistance, and it was 8 ohms, across the cap? This is because of measuring in the circuit? Perhaps because I was feeding the other caps(in parallel, or other loads) with the current form positive multimeter lead and the negative was measuring a lower voltage than it should have thus producing a lower resistance reading?
                Those caps are connected to the VRM line (0.8-1.3V) 1.5-1.8V rail is for DDR3/2 and you might have a low reading if the processor is in the socket or while the caps in parallel are charging up.

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