MOSFET? Is its voltage reading normal?

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  • alro7779
    Alex
    • May 2025
    • 31
    • Mexico
    #1

    MOSFET? Is its voltage reading normal?

    Hello, guys!
    Got this 8-pin MOSFET (I presume) on the motherboard that I'm still trying to repair (HP Stream 11-ah117wm DAY0HGMB6C1 REV:C), close to the DC IN connector, and when I read voltage on Drain (5-8 pins) and Source (1-3 pins), I got the 19.81 VDC of the DC IN on each, but on the Gate (pin 4) it's 25 VDC. Is it normal? Now, I'm not quite sure the component is a MOSFET, but it looks like, and since it has the printed code on it totally unreadable, I can't try to find the datasheet. Can anyone give me a hand on this? Or maybe ff there's some MOSFET tutorial or something that you can recommend me to check out?
    Thanks in advance!

    Tags: None
    • harp
      Badcaps Veteran
      • Jun 2022
      • 570
      • Planet Earth
      #2
      On input mosfets it is normal that voltage on gate is about 6v higher then source in order to mosfet switch on with low internal resistance (few miliohm). That results almost neglible voltage drop between source and drain, and helps to mosfets do not over heat. If is voltage on gate lower, eg equal with source, mosfet will switch on with higher resistance (few ohm) which will results big voltage drop on drain and occasionally burn up mosfet...

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        • alro7779
          Alex
          • May 2025
          • 31
          • Mexico
          #3
          Thanks for telling me that, bro. Now I know that voltage is normal. However, I'll have to keep searching for the problem to be fixed (haven't found the culprit of not having video).

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