Technical Support Thinkpad T490s problem with posting

[LowVoltage]

Hello,

I am having a problem with laptop Lenovo Thinkpad T490s.

At first everything was working correctly, laptop booted, installed OS and drivers without a problem. Then all of a sudden after one shutdown from Windows it wouldn't post again. It starts to spin up fans, they got to max speed and Escape button is illuminated.

I've tried flashing multiple bioses that I found online and it wouldn't start with any of them, wouldn't even respond to power button. It starts and responds to power button only when bios that was on it originally is flashed, but doesn't post still, black screen with Escape button illuminated. I also tried clearing ME on original bios and it didn't have any results.
Also one thing I noticed is that it shuts down instantly when it gets stuck on black screen, at one press of a power button. I don't need to hold the power button for long to make it shut down.

Do you have any tips of what I should try next? Could it be problem with EC ?

 

[LowVoltage]

Here is also original bios, I don't have the knowledge to check if it is corrupted, if someone can do that I would be really grateful

 

[Patrick Ribbsaeter]

Hi LowVoltage, lets get your voltage up

Ok, lesson 1. Dont ever start flashing BIOS.. that's a common beginner mistake that can mess things up more.
You need to learn the power on sequences first for each board you work on. Good at least u saved the original BIOS.
Place back the original BIOS. and start over.
Check all power rails first. You can check the coils for voltages(what do u get)??, and also check with the sleep state the board is in: S5, S4, S3, S0.
If fans spin high, something is shorted most likely or some current sense resistor or thermal issue.
SLP_S5 for example. Check voltages for the SMC, bios, VCCRTC, RTCRST etc. Don't just assume its BIOS!

Do you have ECON, ECRST, VCCRTC, RSMRST?
Is any voltage being pulled down? Example: 3.3v showing 0.5v..
Did u check if the clock is working? u have an oscilloscope?
What voltages_/singals do u get on BIOS pins: 1, 2, 3, 6, 7, 8 ??
How much Amp, do you get on SMPS(power supply)..?
Do you have schematics of the board? If so, please share it here.
What's the history of the board?

 

[LowVoltage]

Hi LowVoltage, lets get your voltage up

Ok, lesson 1. Dont ever start flashing BIOS.. that's a common beginner mistake that can mess things up more.
You need to learn the power on sequences first for each board you work on. Good at least u saved the original BIOS.
Place back the original BIOS. and start over.
Check all power rails first. You can check the coils for voltages(what do u get)??, and also check with the sleep state the board is in: S5, S4, S3, S0.
If fans spin high, something is shorted most likely or some current sense resistor or thermal issue.
SLP_S5 for example. Check voltages for the SMC, bios, VCCRTC, RTCRST etc. Don't just assume its BIOS!

Do you have ECON, ECRST, VCCRTC, RSMRST?
Is any voltage being pulled down? Example: 3.3v showing 0.5v..
Did u check if the clock is working? u have an oscilloscope?
What voltages_/singals do u get on BIOS pins: 1, 2, 3, 6, 7, 8 ??
How much Amp, do you get on SMPS(power supply)..?
Do you have schematics of the board? If so, please share it here.
What's the history of the board?

Thanks a lot for the detailed reply, much appreciated

Some of the things you said flew over my head, I'll have to take it slow and go over all of the tutorial videos on your site to get a better understanding of board measurements etc.. and then get back to this comment to try and figure out problem with the laptop.

I'm 22 years old at the moment with no former education of electronics, except for YouTube guides/lessons and the PC repair shop that I work in currently, but their solution to this problem would be board replacement which I believe isn't necessary. Hopefully here I'll be able to learn basics with the video tutorials and work my way up to repairing boards themselves.

 

[Patrick Ribbsaeter]

Thanks a lot for the detailed reply, much appreciated

Some of the things you said flew over my head, I'll have to take it slow and go over all of the tutorial videos on your site to get a better understanding of board measurements etc.. and then get back to this comment to try and figure out problem with the laptop.

I'm 22 years old at the moment with no former education of electronics, except for YouTube guides/lessons and the PC repair shop that I work in currently, but their solution to this problem would be board replacement which I believe isn't necessary. Hopefully here I'll be able to learn basics with the video tutorials and work my way up to repairing boards themselves.

Yes, well answered... My suggestion is that u watch all Videos here and really pay attention to everything, take notes preferably.. if you treat it with seriousness, you will be able to fix the laptop sooner then later.. its a very much ongoing progress, so it will take time. Not long ago I was in your shoes too.. and many others of us. All I can say is sacrifice some free time and take in as much info as you can about repairing laptops, there is a huge upside to having this knowledge today and for the future.
A great attitude, interest and some thinking out of the box is the first key to becoming a successful repairer. and you seem to have it.
If u have any questions, please feel free to post here.
Good luck