Case of study - Lenovo Legion Y530-15ICH

[alex92ayfer]

Hi all!
I am self-taught in motherboard repair and I find myself somewhat lost.

Motherboard name: NM-B701
The info that i have:

The board arrived with a short on the 3VALW line (0.2ohms). I take out the coil and the short is on both sides. I remove the 3VALW AND 5VALW controller (RT6585) and now I only have short on the load side. I inject voltage (2v) into the 3VALW line and with the thermal camera the PCH heats up in one corner. I take it out and now 3VALW is at 270ohms. I inject 3v again and now the EC heats up. I remove it and short is gone (line go the k range in ohms), reprogram BIOS, EC and change the PCH.

And this is how I am now:

The motherboard connected to the lab PSU, take 0.01/0.02A and go something like 0.28/0.30A to end at 0.4A and drop at 0.01/0.02A... Sometimes this in a loop, sometimes this is only one time and you need to press the power button again.

So maybe you have a problem in vs voltages... i think..

And this is where it gets complicated for me...
With the oscilloscope:
Channel 1 - YELLOW - 3VS
Channel 2 - BLUE - 5VS


And i can find any shortcircuit or low resistance on the motherboar...
I don't have VCCCPUCORE. The VCCCPUCORE rail resistance is 2.1Ohms
NVVDD is present and the rail resistance is 0.6ohms...

Any advice on where to go next? I'm kind of lost.
I already removed the audio IC and the network IC, just in case they were causing problems... but no difference
Thanks for you time.

Link to schematic - https://www.badcaps.net/forum/showthread.php?t=90257

Reminder: rules and organization of this section - https://www.badcaps.net/forum/showthread.php?t=117483

.

[tomodachi]

Re: Case of study - Lenovo Legion Y530-15ICH

Did you try with original charger ? Since EC was also damaged there could be some issue along the adapter ID pin, check that too

[reformatt]

Re: Case of study - Lenovo Legion Y530-15ICH

I would normally write something like this off. Likely had overvoltage on both 3V and 5V rails so you can't trust that any IC on those rails survived. Where did you source the PCH from?

[alex92ayfer]

Re: Case of study - Lenovo Legion Y530-15ICH

Did you try with original charger ? Since EC was also damaged there could be some issue along the adapter ID pin, check that too

Hi to all. First at all, thanks!
I try with the original charger, with the same result. And to use the lab power supply i put a resistor (1.2K) in paralel, from ID to GROUND (see it in a forum) to simulate a 130W charger. Same result withouth the resistor.
Ill go to check ID pin. I should have a comunication, right?

I would normally write something like this off. Likely had overvoltage on both 3V and 5V rails so you can't trust that any IC on those rails survived. Where did you source the PCH from?

I know... the 3v low side mosfet was burned. Well no mosfet in there.... just a hole. I needed to rebuild the track from his gate and now i have 3 and 5 volts. The PCH is from Aliexpress. From SUHMS seller...

[reformatt]

Re: Case of study - Lenovo Legion Y530-15ICH

Even though I use SUHMS myself, I wouldn't trust a PCH from China. They're usually pulled off dead boards and not new. Check Sorin's Electronic Repair School YT channel and what he says on PCH's from China....

Last one he got that worked was from Europe I think. All the China ones he's tried simply don't work.

[piernov]

Re: Case of study - Lenovo Legion Y530-15ICH

Used PCH may have Boot Guard enabled.

[alex92ayfer]

Re: Case of study - Lenovo Legion Y530-15ICH

Even though I use SUHMS myself, I wouldn't trust a PCH from China. They're usually pulled off dead boards and not new. Check Sorin's Electronic Repair School YT channel and what he says on PCH's from China....

Last one he got that worked was from Europe I think. All the China ones he's tried simply don't work.

I saw it! I have been a follower of the channel for a long time. I know, it's a lottery... sometimes I have bought bga as a cpu for example... and it worked correctly. But I don't think this one... The pch has a crystal (YH2) that is not oscillating when the machine tries to start.

Although I am a newbie with the oscilloscope and I don't know if I will have it correctly configured to measure crytal.

I'm thinking about re-soldering it. With new balls

[alex92ayfer]

Re: Case of study - Lenovo Legion Y530-15ICH

Used PCH may have Boot Guard enabled.

YES xD but they sell it like original, NEW 100% tested no fake...


I ordered another one. Germany, elecronicloop.

[alex92ayfer]

Re: Case of study - Lenovo Legion Y530-15ICH

Hi to all. The machine is working after reflow the PCH. So my rework process was not well adjusted.
All working fine... BUT when the GPU install the drivers on windows, after some minutes, seconds (random time), the laptop lose the image and frozen.
Having to turn off the machine while leaving the button pressed. When booting and logging in, it loses the image again and freezes.
That's why I think I now have a VRAM or GPU problem. Is MATS compatible with laptop GPUs? Or, it only working with desktop GPU

Thank for all.