NM-A381 Lenovo yoga 3 14 no power

[Featurea]

Hi all,

I have motherboard nm-a381 from lenovo yoga 3 14, on which there is no short circuit anywhere (but 40ohm on 5V was strange), but when plug in to current, converter PU201 (3.3V) and KBC getting hot. So I replaced both, but resistance on PU202 (converter 5V) is still 40ohm. I have second same motherboard and there resistance is in kohm... I have no idea what to do now and would really appreciate any help.

[mielta]

Re: NM-A381 Lenovo yoga 3 14 no power

Hi
open PJ206 and Mesure on which side are 40Ohm
And check USB-Ports and USB-Power

[Featurea]

Re: NM-A381 Lenovo yoga 3 14 no power

After opening PJ206 I found that PU301 is faulty and has short on PQ302 (gate with source). PQ301 has small hole on it, I think it is broken too. Is there a chance that this motherboard will be alive once again? What should I do now? Replace this transistors and PU301?

[mielta]

Re: NM-A381 Lenovo yoga 3 14 no power

Yes change Pu301 ,PQ301 +302 and before Power on check if there any other short

[Featurea]

Re: NM-A381 Lenovo yoga 3 14 no power

So I replaced PU301,PQ301 and PQ302. Now on PU202 with opened PJ206 I have 13kohm so thats great, but after closing PJ206 it drops to 300ohm... I soldered out U56 and on +5ALW pin I have ~300ohm and on +5vs pin I have 260ohm... Tried to solder out some elements like U8, but no change... Any idea where or how looking for next bad element? I would really apprecciate any help

[Sephir0th]

Re: NM-A381 Lenovo yoga 3 14 no power

Once i Had both USB Switches and the VRM Controller bad causing Low resistance to GND at 5V Rail in this Board. You might be lucky but can be a rabbit hole too.