Troubleshoting Seasonic KM3 based PSU, Advise please

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  • mrcliem
    Member
    • Mar 2020
    • 25
    • Indonesia
    #1

    Troubleshoting Seasonic KM3 based PSU, Advise please

    Hello..
    I have CM V series that wont turn on...
    No voltage on +5VSB and PS_OM pin...

    The board layout exactly like in this thread
    https://www.badcaps.net/forum/showthread.php?p=908291

    after reading the thread above... I measure the voltage on those mosfet ( U3 and U4 )

    U4
    Drain pin : 200v, Gate 2,72V and nothing on S pin (0v).

    U3
    Drain pin : 170v, Gate 2,72V and nothing on S pin (0v).

    I assumes the voltage on Gate pin should turn the mosfet ON... (please correct me if i'm wrong)

    So i believe those two mosfet are bad...

    I have tried to find the compatible replacement, but I cant find with 600v Vdss

    I notice there is un populate resistor next to the mosfet, which i believe its function to "bypass" the mosfet

    on U4=R226
    on U3=R225

    So my question are, is it really bad mosfet ? if it is, can i just bypass it with placing a resisitor ? with what resistor value ?

    Thank you... Appreciate all your help and input....
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