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testing voltage of unknown SMD caps

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    testing voltage of unknown SMD caps

    usually i have to replace motherboard caps (0805 SMD) ...
    the most used (and usually shorted) is the 4.7 uF 25V (HP boards)

    i have a lot of donnor boards... and i take some caps (same size) i measure the capacity using 2 different multimeters (when CAPS are removed from board)

    when i found a 4.4 or 4.5 uF caps i place 19V at the sides and i watch if they blow...(or maybe just start absorbing some milliAmperes)

    i was sopposing that if the caps are not blowing the voltage can be 25 (or in some rare cases 50V) and i use them as a replacement for the bad one.

    is this right ? or a 6.3V cap can stay cold at 19V ?

    or i need to try with high frequency voltages???
    Last edited by Bartoloni; 06-23-2021, 11:39 AM.

    #2
    Re: testing voltage of unknown SMD caps

    examine pcb before cap desolder. we can get idea of how much voltage on these caps. for example, caps connected with 12V line, at least rated for 16V.

    voltage test I think useless. ceramic caps have no sharp voltage margin like tantalum.
    I've tested processor vrm output smd ceramic caps (1205, 10uF, vcore of less than 1.5v) with 24V. nothing happened

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      #3
      Re: testing voltage of unknown SMD caps

      should we expect a test that will determine the max voltage by blowing / breakdown of the MLCC?

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        #4
        Re: testing voltage of unknown SMD caps

        Originally posted by pavithra_uk View Post
        examine pcb before cap desolder.
        usually i do that ... but sometimes the capcs are on not related to a switching power supply... and it's hard to identify how they are used.

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