Lenovo Yoga 2 13 doesn't start

[Survivor2020]

Hi, i have a Lenovo Yoga 2 13 from 2014, that I've used only ~500-600 hours. I've recently started to use it more frequently and I really need to resuscitate this baby

A couple of days ago I tried to charge a portable USB battery from one of the laptop's USB ports and it turned off a few seconds right after connecting it.

When I press the power button to start it, the power light turns on white and then turns off and nothing happens (e.g., screen is black, keyboard doesn't lit, fan doesn't start) then it shuts down. Despite it being off, I notice that it gets hot near the fan even after the power light is off. If I connect it to AC, the charging light is lit and white (i.e., works correctly and battery is charged). It seems like the power source works, but power doesn't get to the devices - hopefully the motherboard is fine.

I've removed the back cover, disconnected the battery, reconnected and tried to turn it on, but nothing changed. The CMOS battery is soldered, so I couldn't take it off easily. When I look inside, i don't see anything suspicious (according to my knowledge) and it doesn't have a burnt smell.

Would you guys have any advice on what the problem/solution might be or how I can test further to identify it? I'm an electrical engineer and I have a multimeter to test, but I'm not an electronic professional so won't be able to resolder/solder stuff.

I've included a couple pictures in case they help.

https://ibb.co/jM1Hmcj
https://ibb.co/68Xs1wW


Thanks in advance for the help and I look forward to hearing from you.

[Vesko356]

Re: Lenovo Yoga 2 13 doesn't start

Look under cmos battery - (look for PJ401 and PJ402) disconnect the battery and the charger, and measure resistance to ground at these two points, also inspect both usb for any bent pins. Left one (with the blue plastic) especially. Also disconnect ribbon cable for the right usb board, and measure values again.

Edit - image added:

[Survivor2020]

Re: Lenovo Yoga 2 13 doesn't start

Thanks a lot Vesko356. I've measured the resistance to ground (using the USB metallic outside as ground) and I got the following:

+ PJ401: very little resistance in the order of 10-30ohms
+ PJ402: high resistance in the order of 100k-M ohms

The measures don't vary if I take them with the right USB ribbon cable connected or disconnected from the board and
pins in both USB ports look perfectly fine.

I've noticed that when I connect the battery back, even without pressing the power button, the area around the fan gets pretty hot.

In case this is relevant, I connected the power bank to charge in the left USB port, the one with the blue plastic, right before the laptop stopped working.

Thanks again and I look forward to hearing your thoughts.

[Vesko356]

Re: Lenovo Yoga 2 13 doesn't start

Thanks a lot Vesko356. I've measured the resistance to ground (using the USB metallic outside as ground) and I got the following:

+ PJ401: very little resistance in the order of 10-30ohms
+ PJ402: high resistance in the order of 100k-M ohms

The measures don't vary if I take them with the right USB ribbon cable connected or disconnected from the board and
pins in both USB ports look perfectly fine.

I've noticed that when I connect the battery back, even without pressing the power button, the area around the fan gets pretty hot.

In case this is relevant, I connected the power bank to charge in the left USB port, the one with the blue plastic, right before the laptop stopped working.

Thanks again and I look forward to hearing your thoughts.

I have a bad news for you I'm afraid, but to confirm - take down the heat pipe, connect the battery or charger and touch the PCH (CPU and PCH is in a single-chip package) see the image below. If it's get hot quickly will be a game over situation. If not (but 99% is) check the ENE controller (KB9012QF) there is a small chance that this chip is the problem too.
P.S. Be careful not to burn your finger.

[Survivor2020]

Re: Lenovo Yoga 2 13 doesn't start

Thanks again for the quick reply. Unfortunately, I'm afraid that your intuition was right. It seems that the PCH heats up just when I connect the AC cable and press the power button, or when I connect the battery, which obviously shouldn't happen while the laptop is off.
When you say a 'game over situation', what do you mean? Is there any fix? Does it mean getting a new chip, a new motherboard? Throwing the whole thing to trash?
Also, would you have any hypothesis on what happened to the PCH or why this happened? Why does it get hot?

Connecting a device to charge from the USB port should be harmless for the computer as it's just a source connected to a load, right? apparently not
Thanks again for your help

[Spider1211]

Re: Lenovo Yoga 2 13 doesn't start

Plugging the usb could just be an unlucky coincidence. By "game over" OP most likely meant that the SOC (pch + cpu) will need to be replaced which requires professional equipment and knowhow as well as not being cheap. It properly would be cheaper to buy a replacement motherboard.

The most likely reason in you case is the high-side mosfet built into driver IC (black square thingy to the left of the grey square (coil)) is shorted which therefore sends main DC voltage (usually 19V) directly to the SOC (which requires typically around 1.05V depending which rail it os). As you may have guessed, sending 19V to a chip that requries a only about 1V will kill it.

I've had this very issue a few times where the all in one driver chip failed. Usually the laptop should cut power if such issue happens but not always apparently.

[Vesko356]

Re: Lenovo Yoga 2 13 doesn't start

Thanks again for the quick reply. Unfortunately, I'm afraid that your intuition was right. It seems that the PCH heats up just when I connect the AC cable and press the power button, or when I connect the battery, which obviously shouldn't happen while the laptop is off.
When you say a 'game over situation', what do you mean? Is there any fix? Does it mean getting a new chip, a new motherboard? Throwing the whole thing to trash?

I said game over because the whole chip must be replaced, but in case of Lenovo machines unfortunately there is a lot of compound at the edges of the chip (and under), and in most cases in the removal process some pads are ripped off the board, so success rate of the operation is low, but beside that fact the parts and the labor for this are expensive, and most probably replacing the motherboard is the cheapest solution.

Also, would you have any hypothesis on what happened to the PCH or why this happened? Why does it get hot?

Connecting a device to charge from the USB port should be harmless for the computer as it's just a source connected to a load, right? apparently not
Thanks again for your help

Why does it get hot? Because the PCH is shorted, and the 3.3V ALW power supply is supplying shorted rail and is getting hot (along with the PCH itself as a cause of the short). It's not your fault, first of all this defect is typical for that model, along with the fragile USB3 (blue) port, or maybe the usb battery you tried to charge is faulty (faulty connector or shorted data pins or cable itself), but in general charging usb devices from the laptop is not a good idea, especially with this model.

Edit:

The most likely reason in you case is the high-side mosfet built into driver IC (black square thingy to the left of the grey square (coil)) is shorted which therefore sends main DC voltage (usually 19V) directly to the SOC (which requires typically around 1.05V depending which rail it os). As you may have guessed, sending 19V to a chip that requries a only about 1V will kill it.

Not the case here, step-down DC-DC regulator (SY8208BQNC) is OK with 99% of the boards, if the jumper PJ401 is opened there is steady 3.3V, so as I said this is a typical fault with this platform, in most cases related with shorted usb data lines.

[Survivor2020]

Re: Lenovo Yoga 2 13 doesn't start

Vesko356, spider1211, thanks a lot for your detailed replies. I really appreciate it. Sorry for my delayed reply.

I'll explore options to replace the motherboard and try to save the laptop if I find an economically reasonable way to do it just for the fun and the personal satisfaction to fix it.

Meanwhile, I can't wait, so I've bought a new laptop and need to transfer data from the old one. I've learned my lesson to be careful every time I connect electronic parts (as it seems these connections are not always harmless), so I wanted to double check with you the best way to extract the data from the old laptop's HDD (as i have some important data that is not backed up (another lesson learned) and can't risk doing something wrong and lose it.

My plan is to buy a USB enclosure, install the old HDD and connect it to the new laptop. The old one runs on Windows 8.1 and I have files i need to retrieve from it. I'm not sure if there will be any security checks that prevent me from doing so this way as some files are in the old windows' desktop folder and might require authentication to see them. The second option I'm considering is to try to boot the new computer from the USB HDD, log in the old windows and upload the files to the cloud. Do you have any advice or warnings on what to do/not to do to get the data out safely?

Thanks again for the help! You guys (and this forum) rock.

[Vesko356]

Re: Lenovo Yoga 2 13 doesn't start

Vesko356, spider1211, thanks a lot for your detailed replies. I really appreciate it.

You're welcome. I'm sorry this case ended to a not repairable situation.

Meanwhile, I can't wait, so I've bought a new laptop and need to transfer data from the old one. I've learned my lesson to be careful every time I connect electronic parts (as it seems these connections are not always harmless), so I wanted to double check with you the best way to extract the data from the old laptop's HDD (as i have some important data that is not backed up (another lesson learned) and can't risk doing something wrong and lose it.

My plan is to buy a USB enclosure, install the old HDD and connect it to the new laptop. The old one runs on Windows 8.1 and I have files i need to retrieve from it. I'm not sure if there will be any security checks that prevent me from doing so this way as some files are in the old windows' desktop folder and might require authentication to see them. The second option I'm considering is to try to boot the new computer from the USB HDD, log in the old windows and upload the files to the cloud. Do you have any advice or warnings on what to do/not to do to get the data out safely?

Thanks again for the help! You guys (and this forum) rock.

Your plan A (USB enclosure), and plan B (try to boot the new computer from the USB HDD) seems OK, but in your case the HDD is a little unusual one (5mm Ultra slim), and it uses SFF-8784 edge connector instead of usual SATA, so it'll be hard to find appropriate USB enclosure or cable. It must be something like this:

[Survivor2020]

Re: Lenovo Yoga 2 13 doesn't start

Thanks Vesko356, I just realized that this hard disk is a bit unusual - when it rains, it pours! Fortunately, I found the USB enclosure on Amazon and I'm waiting to receive it tomorrow to test. I'll post how the story unfolds. Fingers crossed!