Lenovo ThinkBook 13s no power on

[koby058]

hi

I have this Lenovo ThinkBook 13s-IML and it have no power

19v is present on DCIN pin 17 of charger ic (page 59 on attached schematic)

the issue is that +VSYS is 0.5v pin 3 of charger ic, and it is all over the board on all voltage regulators

I want to understand where does +VSYS is generated and why it is only half volt?

can someone help with this please?

[mon2]

Re: Lenovo ThinkBook 13s no power on

See attached for the power path for this main power rail.

Each of the 4 mosfets work together to create this +VSYS rail.

PS: One more episode left for me to watch of Fauda Do not want it to end. Can you put in a good word for me with Lucy Ayoub?? Perhaps she likes dogs?

[reformatt]

Re: Lenovo ThinkBook 13s no power on

All in the sticky from section 1.5. It's a buck-boost converter to accommodate variable input voltages.

https://www.badcaps.net/forum/showthread.php?t=90356

Standard troubleshooting applies, just like BQ series IC's. First check you don't have a short on +VSYS. Also check ACIN for 3.4V, ACOK, MOSFET's Q12H/L, Q23H/L, Q6 etc

[koby058]

Re: Lenovo ThinkBook 13s no power on

Thanks guys

Mon2 every good thing comes to an end, but i will put the good word for you

I can see that both Q12H and Q23H both have a short between gate to source.

Is is reasonable that two mosfets broke at ones ?

[reformatt]

Re: Lenovo ThinkBook 13s no power on

First suspect for me would be an overload on the main power rail. This machine uses charging either via USB-C or an external power brick so check Q5901/Q5902 for damage too. In standard designs, the first MOSFET is usually shorted after a power rail overload.

I'd also be testing with the power brick, rather than USB-C. The latter further complicates matters.