Out of idea on Lenovo Ideapad G405

[degutji]

Hi All,

I've 2 MB of Lenovo G405 on my table,
first MB symptom is power on but no display
- BIOS done
- Reball done
Still no display, still at 0.445 A with PSU ( MB + LCD 0nly )

second MB symptom is power on than goes off immediately
-Bios done
no susp# signal, at pin 116 on EC

Both MB when I plug in the charger has a same symptom, 0.167 A on PSU and the APU chip getting hot ( without press PW Button ). Both MB short to ground at PJ401,PJ502,PJ507 when measure with my DMM, it has 28 Ohm. Is it normal ? I'm out of idea with this MB with all in one chip
Need advise from you all. Best Regard

[atsio]

Re: Out of idea on Lenovo Ideapad G405

Hi All,

Both MB when I plug in the charger has a same symptom, 0.167 A on PSU and the APU chip getting hot ( without press PW Button ). Both MB short to ground at PJ401,PJ502,PJ507 when measure with my DMM, it has 28 Ohm. Is it normal ? I'm out of idea with this MB with all in one chip
Need advise from you all. Best Regard

0.167 shows a short, also the 28ohm on the 3.3v line. Remove solder from both PJ401 and PJ502 and check resistance on both pads on each jumper to determine which side is shorted.

[degutji]

Re: Out of idea on Lenovo Ideapad G405

Thank's for your quick replay atsio,

+3VALW pad short to GND after remove the solder

Regards

[atsio]

Re: Out of idea on Lenovo Ideapad G405

Inject 1v and up to 0,5 amp on the 3.3valw line to see what is getting hot.

[degutji]

Re: Out of idea on Lenovo Ideapad G405

Inject 1v and up to 0,5 amp on the 3.3valw line to see what is getting hot.

Already, up to 3v about 0,288 A only on PSU, nothing hot with this step. FYI that make me little bit confuse, even +3ALW short to GND, the MB can switch on like a normal but no display ( first MB ) as I mention earlier

[atsio]

Re: Out of idea on Lenovo Ideapad G405

If I understand you well, you have removed the solder from PJ401 and PJ502 and after exposing the 4 pads and checking on each of the 4 you found a short on the pad of the 3valw rail. Probably the reading is 28ohm.
How do you check for what is getting hot? The proper way is with a thermocouple and the best is an omega thermocouple that immediately responds to temperature differences. Check for what is having a difference in temperature from the rest of the board. Even a difference in 2 to 3 degrees shows that something is wrong with the IC. When you inject current to the 3valw rail you should not have more the 0.02 amps drawn from PSU.
Main suspect for me is APU (because motherboard starts)

[degutji]

Re: Out of idea on Lenovo Ideapad G405

Agree, replace APU chip for the final step. Thanks for you advise atsio, I'm gonna buy that omega thermocouple soon, at least I got some idea now

Regards