Lenovo yoga 3 14 - nm a381 -3V problem

[tesnic]

Hi guys! Thanks in advance to your help. I have a Lenovo yoga 3 14 (mainboard NM-A381). The actual issue, aftter change the shorted KBC, is the impossible to have the 3V. The BQ seems OK (i have 20V, regn, but not the AC_OK (1V only), it was replaced likewise. I replace 3 o 4 times the PU201 (it's very very hot afte connecting the charger) but i dont be able to work properly. All the replacements of these chip are get very hot.. Is possible the replacements of Aliexpress are spoiled, i order new ones from other seller.... But what could be the fault? What measurings can do?

Link to schematic - https://www.badcaps.net/forum/troubl...a381-schematic

Thanks to all!

[mcplslg123]

The way you're attempting to repair this mb is a sure fire way to kill it. A mb needs to be diagnosed properly before jumping on the hot air gun to replace ic's in a random guess.

PU201 is heating up for a reason. Just measure the resistance to GND on pin5 of this IC-very likely its shorted.

[tesnic]

The initial diagnose was EC/KBC shorted... The resistance to groud of pin5 of PU201 is 15K ohms. Thanks for your help.

[tesnic]

Some help? I dont see any short or low impedance anywhere on the laptop...

[mon2]

Is PU201 still running hot? (Úrsula Corberó hot?)

[tesnic]

jajaja Ursula seems always hot!! ;-) Yes, PU201 still running hot... i'm not capable to know why....

[mon2]

Post a clear pic of pu201. Need to review the smd joints and also the placement on the board.

[tesnic]

I upload the pics. In red the start of hot area on the chip... I hope it helps.

[mon2]

See attached. Remove all power. Use a sharp knife to straighten out the bent trace which appears to be shorting. Not sure if this is a factor or not.

[tesnic]

That's not important... i remove the jumper to isolate the 3'3 line...