Thinkpad L590 short circuit +3VAWL, +1.05VAWL, +1.8VAWL

[danny34]

Hello folks,

I have a Thinkpad L590, motherboard FL590 NM-B931.
According to the owner, 2 power supplies were connected to the two USB-C ports at the same time...

The battery is charging and the power button lights up when you press it. However, the screen remains dark. An external monitor also didn't work.

In addition, the charging LED next to the USB-C port also lights up orange when no battery is installed... There are 12.1V at the battery connection without a battery.

To find the error I was able to find out that +3VAWL, +1.05VAWL and +1.8VAWL have a short circuit to GND.

All other voltages (+5VAWL, +3VL, +3VL_EC, +3VS, 20V from USB-C, B+, ...) are there!

On suspicion, I already unsoldered the UE4001 (IT8227), but it wasn't it.

Does anyone have an idea what I can look for or where these voltages have a common point

Link to schematic --> https://www.badcaps.net/forum/troubl...b931-schematic

[reformatt]

In my experience, a simultaneous short on +3.3V and +1.05V is a bad sign that the PCH is damaged. Take off the heatsink to the CPU, use voltage injection of 1V and check with thermal camera to rule in or out. The smaller of the two dies on the CPU is the PCH part. If you don't have a thermal camera, you can use IPA instead.

[danny34]

Thanks for your answer. Actually, I suspected that but hoped it could be something else.
Unfortunately I don't have a thermal camera. What do you mean by IPA?

[reformatt]

Isopropyl alcohol