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Lenovo Yoga won't turn on anymore.

doudy2 Posted messages 80 Status Member -  
 Scorpion -

Hello,

My Lenovo Yoga 720-15IKB won't turn on, the light indicator does not turn on when I plug in the charger.

I have taken the following actions:

- Tried with a new charger with no result

- Tried resetting with a paperclip in the small RESET hole on the side: no result

- Removed the internal battery and plugged in the charger: nothing

- Removed the internal SSD: no result

- I checked that the female part of the power connector was not damaged.

- Unable to remove the RAM, which is soldered

- This model does not have a CMOS battery for the BIOS...

- This computer has not been subjected to shock or water, the inside is perfectly clean!

I don’t know what else I can do?

I noticed that when I plug in the power, there is a small click as if a relay is activating... this small click is coming from near the power connector on the motherboard. See photo of the motherboard

What do you think?

Thanks in advance for your advice

7 answers

  1.
    txiki Posted messages 6514 Registration date   Status Contributor Last intervention   609
     

    Hello doudy2,

    Your photo unfortunately isn't of any help this time!
    But it is possible that your power supply went into safety mode, hence the slight noise from the relay triggering the power cut to avoid further damage.

    It would be interesting to disconnect the battery (remove it) and the power cable, then press the On/Off button on the laptop several times (10 to 15 times) to discharge the capacitors.
    Alternatively, you could leave everything disconnected (battery and power) for 24 hours.

    Reconnect and test the startup.

    Best regards!

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  2. steph810 Posted messages 1865 Registration date   Status Member Last intervention   152
     

    Hello,

    This little click... it might come from the charging port (hardware), a cold solder joint that didn't hold or has come loose over time.

    Have you tried plugging the charger in while applying leverage up or down, but BE CAREFUL !!!!!! without forcing it?

    PS: Do you have a multimeter??

    If yes, disconnect this plug (Green) and take the voltage measurements (Red)

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  3. doudy2 Posted messages 80 Status Member 3
     

    Thank you for your answers.

    I left the battery disconnected all night, then I pressed the On/Off button on the computer several times (10, 15 times) to discharge the capacitors, but I still have the same problem.

    I also tried plugging in the charger by leveraging it up or down, but no results.

    I have measuring instruments (multimeter and oscilloscope) but I don't really know how to use the oscilloscope (it would be an opportunity to learn!).

    I measured the voltage between the two red wires: 0V (see the photo).

    I noticed that when the white connector is disconnected and when I plug in the charger, I no longer hear the small click of the relay...

    Here is the setup for measuring the voltage:

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    1. steph810 Posted messages 1865 Registration date   Status Member Last intervention   152
       

      Have you tried booting without this connector?

      Just with the battery?

      And measure the voltage of the red and black wires.

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  4. doudy2 Posted messages 80 Status Member 3
     

    It won't start without this connector and only on the battery. But the voltage taken from the battery output (red and black wires) shows 0V.

    On the unplugged white connector, the voltage between red and black is 20.59V:

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    1. steph810 Posted messages 1865 Registration date   Status Member Last intervention   152
       

      OK in red the multimeter test points.

      Connect the charger and take the voltage at the red point.

      In blue, order and note the values.

      Multimeter grounded next to an M2X5 screw on copper (black), the other on the red point.

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  6. doudy2 Posted messages 80 Status Member 3
     

    Components 1 and 2 are coated with a kind of varnish that prevents contact

    3: varies very quickly from 0.400v to 0.800v

    4: varies very quickly from 0.400v to approximately 1.000v

    5: varies very quickly from 0.400v to approximately 1.000v

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    1. steph810 Posted messages 1865 Registration date   Status Member Last intervention   152
       

      At point 3, test all the pins of the MOS and to the left of the number 3, the resistance or inductance voltage on both sides.

      For the connections, disconnect the power supply and lightly scratch the varnish with the probe tip.

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      1. doudy2 Posted messages 80 Status Member 3 > steph810 Posted messages 1865 Registration date   Status Member Last intervention  
         

        After scratching the blue varnish from 1 and 2:

        1: 0.011v

        2: varies very quickly between 0.000v and 0.400v

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  7. doudy2 Posted messages 80 Status Member 3
     

    Pins 1,2,3,4: rapid variation from 0.4 to 0.8v

    Pins 5,6,7,8: rapid variation from 0.4 to 1.0v

    Resistance:

    point A: rapid variation from 0.0v to 0.4v

    point B: rapid variation from 0.0v to 0.2v

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    1. doudy2 Posted messages 80 Status Member 3
       

      Based on these measurements, do you have any idea of the source of the problem?

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      1. steph810 Posted messages 1865 Registration date   Status Member Last intervention   152 > doudy2 Posted messages 80 Status Member
         

        No, I don't have the measurements on hand. I tested all the points and capacitors until I found 19v and checked the power connector, the other part is behind, probably a capacitor or a MOSFET that has blown.

        You can also look for a hot spot with your finger.

        Check these electrolytic capacitors. They seem to have blown.

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      2. doudy2 Posted messages 80 Status Member 3 > steph810 Posted messages 1865 Registration date   Status Member Last intervention  
         

        I measured the voltages at the power pins on legs 1, 2, 3, 4, and 5 (see below) and it seems strange to me because the voltages are very low compared to the first measurements taken on the white plug disconnected between the red and black wires: 20.59V

        So voltages on the legs:

        2-4: varies between 0.400V and 1.500V

        2-5: varies between 0.400V and 1.500V

        3-4: varies between 0.400V and 1.500V

        3-5: varies between 0.400V and 1.500V

        I did not take measurements on the other side of the motherboard because I have not disassembled it yet.

        And upon touching, one area is warmer without being burning: red circle.

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      3. doudy2 Posted messages 80 Status Member 3 > steph810 Posted messages 1865 Registration date   Status Member Last intervention  
         

        Close-up, visually these condos don't seem beaten up. How can we test them?

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  8. Scorpion
     

    Hello, I have the same problem with the Yoga 7, how did you manage it please? I think Lenovo should issue recalls.

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