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Yoga C940 - Won't Turn On w/ Power Button

2020-01-01, 10:18 AM

There are many of these posts about the laptop not turning on, and I've followed guidance in quite a few relating to Hybrid sleep -- no luck. Here's the situation:

 

Since I received the laptop in October 2019, until December 2019: Infrequently, when trying to wake the computer from Sleep, it would not respond. Power button LED would keep glowing/fading as it does in sleep. No response from the machine. To fix, I held power down until it turned off, then turned back on.

 

In December 2019: The above was occuring more regularly, rapidly leading to 31 December

 

31 December:

Now, when I got to the turn-on point, the keyboard lights up, and the power button LED was solid, but no light to the screen; no LENOVO boot splash screen. Fans whir lightly after a minute. This is all while plugged in, i.e. power connection LED is on. Same if I unplug it.

To start my computer now, I must use the NOVO button, in which case it works first time.

 

The Power button obviously "works", but the machine doesn't do anything.

 

Any thoughts? I have a warranty repair person due to come by the end of this week or else Monday; but I'm keen to have a better idea of what this is before then.

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  • Message 2 of 17

Re: Yoga C940 - Won't Turn On w/ Power Button

2020-01-01, 10:36 AM

Hi ,

 

Welcome to the Community.

 

We have a couple of steps for you to try.

 

First, do a power drain. Remove all peripheral devices connected to the laptop then press and hold the power button for 15-20 seconds.

 

Once done, update the Windows and drivers (Display driver and BIOS) using the Lenovo Vantage. You may download and learn more about the Lenovo Vantage here

 

We also suggest turning off the fast start up

 

Hope it helps.

Auxen



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Re: Yoga C940 - Won't Turn On w/ Power Button

2020-01-01, 11:06 AM

Thanks for starting to help troublehsoot, @Auxen_Lenovo

 


 First, do a power drain. Remove all peripheral devices connected to the laptop then press and hold the power button for 15-20 seconds.

 Removed all conneccting cables (including power). I held the power button for 15-20 seconds after using the power button to turn the laptop off. This has lead to a small breakthrough in that I no longer need to use the NOVO button to turn it on. So I can boot if I do a power drain, as you say. Power drain even worked with the power plugged in (tried this a few times)

 


Once done, update the Windows and drivers (Display driver and BIOS) using the Lenovo Vantage. You may download and learn more about the Lenovo Vantage here

 

 All Windows updates complete. Feature update 1909 had to be updated; done now. Lenovo Vantage says Last Update: 18/11/2019, but it also says the only update that it has had to install is a Pen Driver... I feel like there might be more updates, but "Check for updates" concludes "No Updates are available. Your system is up to date." I've gone online to the Lenovo "3 Steps to Solution", and checked for updates there -- also says no updates for me.

 

Next step? Or Thoughts given the development on the first item?

 


 

We also suggest turning off the fast start up

 Turn off fast start up: Done. No effect on start-up / wake situation.

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  • Message 4 of 17

Re: Yoga C940 - Won't Turn On w/ Power Button

2020-01-01, 21:26 PM

Hi again. I'm just conscious that I provided a quick and complete response to the initial troubleshooting questions -- is there anything that can be picked up from the results?

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Re: Yoga C940 - Won't Turn On w/ Power Button

2020-01-01, 22:32 PM
By any chance, did you initially undervolt the c940 and it unexpectedly crashed and then the not waking from sleep/boot issue started to happen? Cuz that's exactly what happened with 2 c940's I've owned so far. The fix for not waking from sleep for me was to not to run heavy tasks on an undervolt of -80mv and leave it at -50mv for when gaming. And downloading Windows 1909 from their site to fix the wake from sleep issue. The not booting at all issue was fixed as follows: when it doesn't want to boot (keyboard/fans go on, black screen) force shut it down leaving the power button pressed. Then, wait a few minutes. Preferably 4-5 minutes, and then turn it on. If it still persists, try leaving it a lot more (10 is exaggerated but it should work) and try turning it on there. If that doesn't work and your issue didn't arise from an undervolt at all, I'd suggest leaving it to the Lenovo repair guy since maybe your system came undervolted or badly programmed, since it's too much of a coincidence that what you're going through is exactly what I went through on 2 undervolted c940's.
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  • Message 6 of 17

Re: Yoga C940 - Won't Turn On w/ Power Button

2020-01-01, 22:37 PM

 wrote:
By any chance, did you initially undervolt the c940 and it unexpectedly crashed and then the not waking from sleep/boot issue started to happen? Cuz that's exactly what happened with 2 c940's I've owned so far. The fix for not waking from sleep for me was to not to run heavy tasks on an undervolt of -80mv and leave it at -50mv for when gaming. And downloading Windows 1909 from their site to fix the wake from sleep issue. The not booting at all issue was fixed as follows: when it doesn't want to boot (keyboard/fans go on, black screen) force shut it down leaving the power button pressed. Then, wait a few minutes. Preferably 4-5 minutes, and then turn it on. If it still persists, try leaving it a lot more (10 is exaggerated but it should work) and try turning it on there. If that doesn't work and your issue didn't arise from an undervolt at all, I'd suggest leaving it to the Lenovo repair guy since maybe your system came undervolted or badly programmed, since it's too much of a coincidence that what you're going through is exactly what I went through on 2 undervolted c940's.

Nope, nothing fancy applied in my case, ie no undervolting or anything like that.

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Re: Yoga C940 - Won't Turn On w/ Power Button

2020-01-01, 23:19 PM
I see. Try downloading Windows 1909 (even if you already have it installed) directly from their site (https://www.microsoft.com/en-us/software-download/windows10) to see if that fixes the issue for you, since it did fix it on my end. If you're down to trying a hard reset, select to keep no files from the windows 1909 download so it does a clean install for you.
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  • Message 8 of 17

Re: Yoga C940 - Won't Turn On w/ Power Button

2020-01-02, 17:50 PM

I'm afraid I'm hesitant to do a clean install in this case. I don't have any good explanation for a clean install solving the problem, particularly as I cannot connect the Windows installation to the symptoms whereby the computer will start if the power button is held down long enough / Bios button works.

 

To add further information:

 

If I Shut Down the computer properly, it turns back on -- no problem. It only won't turn back on if it's put to Sleep, or hard shut-down (holding the power button for ~5 seconds).

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  • Message 9 of 17

Re: Yoga C940 - Won't Turn On w/ Power Button

2020-01-02, 18:01 PM

Hi @Auxen_Lenovo

 

Just following up on this again. See my full response to your first post above.

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Re: Yoga C940 - Won't Turn On w/ Power Button

2020-01-02, 19:03 PM

It might be weird to connect what seems to be hardware problems with software ones, but remember that I faced basically your same exact issue except that my cause seems to be different than yours. If you don't want to try a clean install (deleting everything) that's fine, but I would still heavily suggest downloading Windows 10 1909 and keep all the files and apps you have, since that on my end fixed my issue. That option doesn't delete anything at all on your c940 and only takes about ~10 minutes to do (downloading and installing times considered) https://www.microsoft.com/software-download/windows10

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