New laptop with random issue, unsure if to try to return

RandomStyuf · October 29, 2019

Hi,

I'm sorry if this isn't the right forum, I'm not sure where exactly this would go.

I recently (18 days ago) bought the Lenovo Yoga C940. It's the new convertible with the 10nm ice lake CPU, which competes with the Dell XPS 13 2-in-1.

Not sure if it's relevant in this case but to follow the sticky: The specs are: i7 1065G7, with 16GB of LPDDR4X and a 1TB NVMe SSD.

Yesterday night, I was working on my computer and had some network issues (I don't know if they are related to the laptop, they could be my cheapo access point) and decided to try to restart to see if they get solved. I pressed on the restart button in the Windows start menu, and then realized I had an unsaved document open so I cancelled the restart. I was connected to an external monitor, so my eyes went to the external display to save the document and when they moved back to the laptop display it was completely off (no back-light at least).

I wasn't sure what to do so I went ahead with the restart, and when it rebooted, the laptop's monitor stayed off. This includes during POST, (when the Lenovo logo shows and you can go into the "BIOS"/UEFI/however-it's-now-called settings) which to me means that it isn't a driver or OS issue. The external monitor still worked so I logged into Windows and saw that the display settings showed that there was only one monitor (my external Samsung display) and the device manager also showed only the one monitor attached. Although the monitor was not detected, the webcam did still work, and when I rotated the screen (over the 180 degrees point) it did detect it and ask me if I want to use tablet mode. I don't know if it's all wired together or not but if it is at least those functions continued to work. I tried shutting down and booting detached from the external display, and the problem was not solved. I also didn't see any events in the Event Viewer that looked relevant (such as hardware disconnects or driver crashes or whatever could be related)

About an hour later, as a last Hail Mary I decided to turn off the laptop and press the power button for 30 seconds and then try to boot. To my surprise the laptop booted and the screen came back to life. I used it this morning and I don't see any issues with it.

Now I'm unsure of what to do going forward. I think I'm outside the window where I can request to return or replace the laptop (although I can try and argue with them) but I'm not sure if I should or not. Right now the laptop works, but I don't know what caused the issue, and I'm not sure if it points to some underlying issue that could cause me an issue down the line when it would be even harder to request a replacement unit.

So my question is really: Do any of you have any idea of what could cause this? And do you think it might be something that I should worry about for the long term or just some one-off hardware bug?

Thanks in advance for all the advice and sorry if this is too long. I just wanted to make sure I'm not leaving out anything that could be relevant.

(Also: my best theory so far is that somehow in the initial aborted restart caused the display controller to somehow enter a funky state and that both restarts and the shut down (which was short, I shut the laptop down and then turned it back on 3-5 seconds later) were too short to completely power cycle the controller, but I'm also not sure if in such a case I wouldn't have seen at least something in the device manager or Event viewer...)

Las0r · October 29, 2019

Hi!

It sounds like your theory is just about right, I did some quick googling and found that Lenovo Support actually recommends doing a hard shutdown of the computer without the A/C Adapter plugged in, making it re-do the full power cycle before turning on completely.

It seems like a known issue and you should be happy it (hopefully) only was the Power Cycle that didn't go through fully, have you been able to reproduce the error to actually confirm it could be the hard shutdown that solves it?

RandomStyuf · October 29, 2019

I haven't been able to reproduce the problem (I haven't tried to reproduce the exact same conditions, I'll do it when I get home and can use my external monitor).

Reading on the Lenovo Support forums I've found people who aren't Lenovo employees talking about it being a problem with the GPU (in other models, haven't found something about this model yet), but I'm not sure if that's something I should be worried about here because an external monitor did work, and I assume that if the GPU had a problem I wouldn't have been able to use the external monitor (or maybe the computer in general, because it's integrated onto the CPU?)...

Do you have any thoughts about whether this is something I should be worried about for the long term?