Lenovo Yoga 520-14IKB not powering on

[hinisa]

Hi,

I'm not a technician so plase bear with me. Unfortunately I couldn't find anyone nearby doing motherboard repairs so I'd be happy if I can narrow down the issue as much as possible myself.

Issue: Laptop doesn't power on.

• No backlight.
• Fans aren't spinning.
• Battery seems to be charging when plugged in to AC. (judging by the solid white led indicator.)
• I've unplugged battery cable and CMOS cable. Tried pressing power button for 30 seconds etc. Still not powering on.
• When I plug in the AC, but not press the power on button yet, I can feel heatsink is warm (battery&CMOS are still unplugged)
  
• Then when I press the power on button, indicator light is on solid white for 5 seconds, then it goes out again (battery&CMOS are still unplugged)
  

Story
This is computer of a relative. Laptop was working fine. I opened the back cover because I was planning to upgrade the RAM and wanted to see what was installed. Still working fine. I upgraded the BIOS. Rebooted. Still working fine. Last thing at the night I started the Windows built-in memtest tool. It passed. I rebooted Windows and powered off the computer knowing everything was OK.

Next day I put back the back cover, then tried to power on the computer and it didn't start

My relative's coworker IT guy send it to a repair shop but they didn't do anything at all (I don't know the details but from the looks of it they've only done basic troubleshooting - and since there's no backlight and fan spinup they didn't go further and written it off)

Now we're stuck with a beautiful paperweight.

Specs

• Lenovo Yoga 520-14IKB
• Motherboard: LA-E541P - CIUYA_YB_SA_SB_SD Rev. 2A

schematic: https://www.badcaps.net/forum/showpo...12&postcount=8

Service manual: https://cdn.badcaps-static.com/pdfs/...cf316e1e1f.pdf

[mcplslg123]

Re: Lenovo Yoga 520-14IKB not powering on

Heatsink warm without pressing power button- Very likely PCH part of SOC(Smaller die) is shorted.

[hinisa]

Re: Lenovo Yoga 520-14IKB not powering on

Heatsink warm without pressing power button- Very likely PCH part of SOC(Smaller die) is shorted.

Thanks, sir, that was spot on.

I removed the heatsink and indeed small die is hottest.

Can it be repaired on board component-wise? Or the SoC chip must be replaced altogether?

Is there a further probing I can do with a cheap multimeter?


I'm adding a picture of soc area:



https://i.ibb.co/wJJDvfF/20210818-122916.jpg

[SMDFlea]

Re: Lenovo Yoga 520-14IKB not powering on

Did you have a metal cover over the ram slot,and did you pry it up with a metal tool

[hinisa]

Re: Lenovo Yoga 520-14IKB not powering on

Did you have a metal cover over the ram slot,and did you pry it up with a metal tool

Yes, I pryed it with plastic tool, it plopped right up.

More details:

Last time PC was working I was doing "maintainence".

I was planning to do a RAM upgrade, so I removed the back cover did some light cleaning. Ran memtest midnight for a few hours then shut down the PC. Next day I screwed the bottom cover back then it didn't start to my surprise.

Another thing I did was: Plastic hinges were shattered so I sprayed one of those instant freeze adhesives at one corner. I suspect maybe it shorted something, but after that I used the computer for a few more hours and ran memtest etc.

I also did a BIOS upgrade, but then again, it booted after the update fine and even ran memtest yada, yada...

[mcplslg123]

Re: Lenovo Yoga 520-14IKB not powering on

Hmm So SOC is gone. Check resistance on 3V Coil and Bios chip pin8. You can desolder 3V coil and check which side is shorted and apply 1V on the shorted side of coil. You should'nt exceed 1V. You need a dc supply to do this. However, i'm 99% sure your SOC is gone.

[kalilinux25]

Re: Lenovo Yoga 520-14IKB not powering on

I have a issue to this board I'm just having 8milliamp of power consumption to the board and Also i've knock off the L101 . Can I just jumper it or need to change I cant find a new one also..

First
SHorted EC
Flashed bios, ec bin

only taking 8 milliamp if powered

[mon2]

Re: Lenovo Yoga 520-14IKB not powering on

Yes, the part can be just shorted. The purpose of this inductor is to act like an EMI filter to reduce interference to radio and over the air tv.

[piernov]

Re: Lenovo Yoga 520-14IKB not powering on

Here it's more about filtering the power rail to have a cleaned analog supply for the EC (most likely used by some ADCs for current, voltage or temperature measurements).

[kalilinux25]

Re: Lenovo Yoga 520-14IKB not powering on

Those anyone have a BIOS and EC file? for CIUYA_YB_SA_SB_SD LA-E541P rev 2a 2017-05-02

[mcplslg123]

Re: Lenovo Yoga 520-14IKB not powering on

@Kalilinux25, why not make the request in "BIOS SECTION" ?? You are quite old on this forum-so must be aware of the norms.