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Lenovo Legion 5 high fan spin turns off after 34 seconds

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    #1

    Lenovo Legion 5 high fan spin turns off after 34 seconds

    Hi all,

    I have a Lenovo Legion 5 with a Ryzen 7 series CPU and RTX 3070 GPU. My issue is that it turns on and all seems fine except after a few seconds the fans spin up high and the laptop turns off after 34 seconds.
    I can get into bios and can even boot and login to Windows however after 34 seconds no matter if Im at the bios screen or booted into Windows it will just turn off.

    I have managed to run HWmonitor and the temperatures of the CPU and GPU are fine, I can also touch the heatsync which is warm but not hot.

    I have tried a few new bios but exactly the same thing.

    If I remove US134 which is a thermal sensor then the laptop stays on for 65 seconds before turning off, putting it back it shuts off at 34 seconds again.

    I read on a forum that it maybe the MUX switch which if I disable discrete graphics in the BIOS does not change anything. I could remove the MUX chip but I'm not sure what will happen or what it will prove.

    Any ideas?

    Many thanks








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    #2
    Hi got exactly two same motherboards with this issue one had short on 3v ldo and 3vs line after replacing kbc edp mux and usb c pd controler board start but shuts off after 20-30sec , second same board cpu was dead ( No cristal oscilation) replaced cpu and same story laptop starts shows pictures can enter bios but again shutdown after about 30sec....
    Did you menage to sort this out?

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      #3
      Hi guys, have you figured this one out? I'm having the same issue!

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        #4
        Hi guys, I finally figured it out. My issue was US1 which is a F75303M. It's a temp sensor chip for the CPU.
        Ordered mine from Aliexpress and fitted. Laptop is perfect now.
        Hope this helps.

        Comment

          #5
          Originally posted by twonk9098 View Post
          Hi guys, I finally figured it out. My issue was US1 which is a F75303M. It's a temp sensor chip for the CPU.
          Ordered mine from Aliexpress and fitted. Laptop is perfect now.
          Hope this helps.

          Awesome! How did you find out? Mine started doing this after I have removed the mosfets for the GPU and VRAM as the discrete gpu had a shorted mosfet.

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            #6
            Hi, I removed US1 because it is a sensor IC for the CPU according to the schematics. I noticed upon removal the laptop would stay on for 64 seconds instead of the 34 seconds with it installed. This made me think there was an issue with it therefore replaced it. After replacing it, the laptop worked totally fine. Tested under full load to and the temps got up to 89 degrees at a push.

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              #7
              The other thermal sensor on the board is U134, I believe this one is for the GPU.

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