NM-B471 Lenovo T480s don´t charging

[master3112]

Hi guys
I need help with a Lenovo T480s NM-B471.
The device works via power supply and also via battery. However, the battery is not charging. If I start the device via battery, the power supply is deactivated and the battery is empty at some point.
I have measured and found the following. When the mains adapter is connected, is VSYS= 20V, but this should be 15V. At the PQ102, which is responsible for this, I have 20V at the gate (pin 1). However, 15V should be there. Because the voltage is too high, PQ103, which should charge the battery, remains closed. I have already replaced the PowerController (PU101), same behavior. When the device is running on battery power, VSYS= 11.8V, i.e. the battery voltage. Does anyone have any ideas? THX

[mon2]

Both PQ101 and PQ102 are suspects. Remove all power. Meter in resistance mode.

Measure resistance of:

source & drain
source & gate
gate & drain

of each dual mosfet. Post each measurement. Each must be hundreds of k ohms or more if ok.

[Sephir0th]

Note that these are Dual-Mosfets. But it indeed strongly sounds like PQ101 being internal shorted when getting 20V at VSYS

[master3112]

Thank you friends. I measured the PQ101 and PQ102 at first. However, they were not shorted. When switched off, the PQ101 had normal resistance from pin2 to pin7, which seemed to be ok to me. Unfortunately I didn't have the MOSFET to test it. But as Sephir0th writes, it is a dual mosfet. I looked at the technical data and had an AONY36352 with the same parameters. It worked. So the PQ101 was actually defective. I had never had anything like this before.