Badcaps.net Forum
Go Back   Badcaps Forums > Troubleshooting Hardware & Devices and Electronics Theory > Troubleshooting Laptops, Tablets, and Mobile Devices
Register FAQ Calendar Search Today's Posts Mark Forums Read

 
Thread Tools Display Modes
Old 10-05-2021, 11:29 AM   #1
Featurea
Member
 
Join Date: May 2021
City & State: Poznań
My Country: Polska
I'm a: Knowledge Seeker
Posts: 22
Default NM-A381 Lenovo yoga 3 14 no power

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.
Featurea is offline   Reply With Quote
Old 10-06-2021, 02:24 AM   #2
mielta
Badcaps Veteran
 
Join Date: Apr 2015
City & State: Neuss
My Country: Germany
I'm a: Knowledge Seeker
Posts: 351
Default 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

Last edited by mielta; 10-06-2021 at 02:27 AM..
mielta is offline   Reply With Quote
Old 10-06-2021, 01:35 PM   #3
Featurea
Member
 
Join Date: May 2021
City & State: Poznań
My Country: Polska
I'm a: Knowledge Seeker
Posts: 22
Default 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?
Featurea is offline   Reply With Quote
Old 10-07-2021, 01:57 AM   #4
mielta
Badcaps Veteran
 
Join Date: Apr 2015
City & State: Neuss
My Country: Germany
I'm a: Knowledge Seeker
Posts: 351
Default Re: NM-A381 Lenovo yoga 3 14 no power

Yes change Pu301 ,PQ301 +302 and before Power on check if there any other short
mielta is offline   Reply With Quote
Old 10-17-2021, 12:13 PM   #5
Featurea
Member
 
Join Date: May 2021
City & State: Poznań
My Country: Polska
I'm a: Knowledge Seeker
Posts: 22
Default 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
Featurea is offline   Reply With Quote
Old 10-18-2021, 04:05 PM   #6
Sephir0th
Badcaps Veteran
 
Sephir0th's Avatar
 
Join Date: Oct 2020
City & State: Wangerland
My Country: Deutschland
Line Voltage: 230VAC 50Hz
I'm a: Hobbyist Tech
Posts: 318
Default 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.
Sephir0th is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



Badcaps.net Technical Forums 2003 - 2022
Powered by vBulletin ®
Copyright ©2000 - 2022, Jelsoft Enterprises Ltd.
All times are GMT -6. The time now is 09:36 PM.
Did you find this forum helpful?