Lenovo IdeaPad 3 15ADA05 Model: 81W1, how to disable onboard MICROTEC RAM?

[Visual_vt]

Lenovo IdeaPad 3 15ADA05 Model: 81W1, how to disable onboard MICROTEC RAM?
Laptop freezes, sometimes no picture. POST every time with 4GB additional memory but still freezes in the windows.
SSD and BIOS seems to be OK.
Thank you.

[mcplslg123]

Write the motherboard number here and link schematic if posted in the forum.

[Visual_vt]

MB number: NM-C821, no schematic in the forum, found something on the internet.

Link to schematic - https://www.badcaps.net/forum/troubl...c821-schematic

[Visual_vt]

AL._.EX posted a shematic, can you plese check?
https://www.badcaps.net/forum/troubl...c821-schematic

[mcplslg123]

I've both schematic+BDV for this mb and can share if needed.

[Visual_vt]

Please share, thank you.

[mcplslg123]

Here is the link
https://www.badcaps.net/forum/troubl...atic-boardview

[Visual_vt]

Can anyone help?

Thank you.

[mcplslg123]

Look at page7 in schematic.Its detailed there.. You need to adjust board_id 2-3-4-5

Mention exact markings of your onboard ram if you cant figure it out.

[tomodachi]

Did you make sure the on board memory is corrutpted ? Did you run memtest ?
This model is known for dry solder joints under the CPU and might need a reball to fix the issue.

[mcplslg123]

tomodachi, How you de solder this type of BGA with black underfill?
I most often end up damaging the PCB traces in case of lenovo.
However, replaced SOC/PCH without any issues on other brands.

[tomodachi]

@mcplslg123
There are two types of glue / underfill used on Lenovo boards,dark black and light black / greyish.
I have yet to come across anyone who can remove light black / greyish underfill without damaging the pads or chip.
Black glue is the one that easy to remove.
Under reflow process it softens and becomes flexible and soft, it takes a try or two to to realise how easy it is to remove.
Once you remove the chip it is very easy to clean underfill from chip and the motherboard but remember heat is the key.
During reflow wait till it reaches the melting point
To make sure all balls are melted you can use a thin chip removal blade ( ones used in gsm repairs ) to poke the balls and once you see them melt just insert blade under the bga then start turning blade from gently to hard if necessary, you will see chip will be totally come off the board.
I've done at least 50-70 reball on this model and none of them came back with bsod / random crash and no display problems again.

[Visual_vt]

Did you make sure the on board memory is corrutpted ? Did you run memtest ?
This model is known for dry solder joints under the CPU and might need a reball to fix the issue.

Yes, memtest is showing errors with onboard ram.
Laptop freezes, sometimes no picture with onboard ram but post every time with 4GB additional memory. But still freezes in the windows...

[mcplslg123]

Thanks @tomadachi for your valuable insights on soc reflow. I value them a lot. Hope this advise of yours will enhance my skill.

[tomodachi]

Thanks @tomadachi for your valuable insights on soc reflow. I value them a lot. Hope this advise of yours will enhance my skill.

I hope to see your succesfull soc reworks here, good luck !