Lenovo T14 nm-c931 1th gen intel 10th DEAD

[Zmay2509]

Hi, I have dead t14 gen1 with nm-c931 motherboard.

Laptop doesn't turn on and does not show any sings of life.(battery is completely flat, do I need it for power on??)

When I connect usb c power adapter it draws 0.02A at 20v, I get voltage 20.5V up to 2nd mosfet and nothing out (PQ0006 before current resistor and buck-boost) when I touch gate pin of PQ0006 with tweezers it opens and I get 20.5v on current resistor;
But even with that "trick" I cant get laptop to turn on, that's probably because BQ25700ARSNR is not happy and not making VSYS15 rail.

from groung to VINT20_IN (after PQ0006 mosfet) I have 31Mohm, between ground and inductor coil I have 45Kohm, and between ground and VSYS15 I have around 1Mohm.

I don't have experience with Lenovo boards and BQ chips so any idea is appreciated (I have thermal camera, DC power supply and oscilloscope if additional measurements are needed)

Thanks

[rumpumpel1]

You don't need a battery to turn it on. A bare board with just a fan should turn on the moment you plug in a charger.
Is the behavior the same for both USB-C connectors?
What happens if you try to power up the board with just a (charged) battery?

[Zmay2509]

Hi, thanks for reply.
When I connect charger to second usb-c port I don't get any voltage.
I don't have charged battery to try :/

[rumpumpel1]

testing with a charged battery is important, because you know if the fault is either before (and including) the battery charger or after the battery charger.

[pc_okay]

Hello friend,

please mesure voltage on pin 4 Of pq05

and Check both mofset 05 & 06 résistance both side
gare <> source
gâte <> drain
drain <> source

Check solder too on both mofset last Time, one mofset was partialy desolder, I think on a similar model.