Troubleshoting Seasonic KM3 based PSU, Advise please

mrcliem

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Join Date: Mar 2020

Posts: 25

Country: Indonesia
#1

Troubleshoting Seasonic KM3 based PSU, Advise please

06-20-2023, 04:09 AM

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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Troubleshoting Seasonic KM3 based PSU, Advise please

Troubleshoting Seasonic KM3 based PSU, Advise please

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