Thinkpad T14s RAM failure diagnosis

[holgerczukayfan3000]

Hey there,

my Lenovo T14s i7-10510 16GB Ram is behaving very unstable. Checking the errors with memtest86+ returns bad adresses all over the memory although it's 8 discrete modules. Somehow i have doubts that the error is rooted in the RAM devices themselves but more in the way they're organized. i'll attach a badram dump from 4 scans.
is someone here who's familiar with issues like that? all the memory devices are soldered with BGAs. not sure if replacing them is actually an option.
i know about electronics, not so much about digital and small things. but also happy to learn and research. really not sure where to start though, any hints

thanks so much for reading this and taking your time.
Warmly,
julian



https://pastebin.com/?__cf_chl_tk=fU...maLJa9qgEZCNTk

[holgerczukayfan3000]

Board No: LCFC NM-C891
i7-10510

Schematics here https://www.badcaps.net/forum/troubl...atic-boardview

[dggn]

Hello,
I have the same problem with this model. Was it possible to solve the fault ? Or maybe someone had such a problem and hints ?

[holgerczukayfan3000]

Hi dggn,

this is a work in progress, for now i replaced the mainboard with an amd type. BUT this turned out to be unstable as well, with different symptoms. (troubles booting a system from usb, random freezes, shutdowns when connected to charger)
i disconnected the battery this afternoon and it's behaving stable up until now. chances that the battery or parts of the power circuit are behaving weirdly? power supplies can have the weirdest effects on systems.
if i find the time in the next days i'll swap back the intel board and do another run of memtest86+ without battery this time, will let you know.
if you decide to try this please get back to me if something changed.

still hoping anyone else jumps on board solving this problem
warmly,
julian

[pc_okay]

Maybe battery is not compatible With your new MB.
I m pretty sure that a battery can't create memory error.

it can't create blue sceen yes, but related to power or ACPI, and Of course unexpected shutdown, maybe freeze.

But try again you Intel board without battery we Will see.

[holgerczukayfan3000]

pc_okay thanks, I think you're right. There's different batteries for amd and intel versions of the board. Mismatching probably causes some mess on the charging controller

running the intel board w/o battery didn't change anything. So any leads on the ram issue? Would be happy to hear about experiences with reflowing

[pc_okay]

Sorry to say that but reflowing Will not work in your case.
Reflowing Works only when chip has Bad solder: symptôms are black screen, laptop can't start Without ram or loose ram. (Maybe freeze too)

When you have random bsod or memtest error you need to replace Bad chip if you can identify them.
or replace all if you can't identify culprit.

if you can't do that by yourself you better find a Good Repair shop or take some training class.

good luck 😊

[holgerczukayfan3000]

hey there,
thanks for your replies! back with some questions.
i was probing on the supply lines for the ram and found some spikes/glitches on the VCC2R5A rail. (+20/-60mV).
how likely is it that the step-down converter for that rail (NB687GQ-C669-Z) is causing the trouble?

i need ideas to source a replacement part. donor board? aliexpress? drop in replacements?

thanks so much in advance! warmly