Lenovo ideapad 510 15ISK- power problem

[huzo]

Hello to all,

i have a mentioned laptop, the board is NM-A751 Rev 1.0,

it turns on when i plug the charger,but no picture and resets in few seconds...

all the voltages are present except VCC_GT, but i think that is normal,because it doesn't use the GPU at startup

The thing is that when it should turn the screen on, it looses all voltages for a moment and they come back up and the process is repeated... there are no shorts found, everything is disconnected from the board,the CPU gets hot ,so everything sholud be fine,but it's not.... i noticed that the CPU has two cores,one is PCH ,other is CPU, PCH doesn't have cooling applied from the heatpipe,it's not cooled at all,but it gets hot,is the PCH dead?

I flashed the bios and noticed when the bios chip is desoldered from the board, the fan spins,and the board doesn't reset,usually when bios chip is on the board,the fan just ticks for a brief moment and so does the display,like it's starting but then the board resets, something is wrong and i can't find out what...

i tried injecting voltages from lab psu, but to na avail...

what to look next?

[huzo]

Re: Lenovo ideapad 510 15ISK- power problem

please,any advice?

[mcplslg123]

Re: Lenovo ideapad 510 15ISK- power problem

Pch heating up a bit is normal. I beleive its a bios issue. You should flash bios extracted from lenovo bios update for your model to avoid confusion and if you dont know how to do that, ask for it in bios section. Look for any corrosion on the mb under microscope.

[huzo]

Re: Lenovo ideapad 510 15ISK- power problem

something is happening when it's about to start...i desoldered power for onboard ram and it acts like it should, it doesn't POST,but neither does reset it self...

something is shorted in the lvds conector, or something like that,but 3.3V for the lcd _on is there for 1-2sec,20V is stable,maybe cmos camera ...ODD and HDD are spinning,so that's ok, wifi card is taken out, i disabled the LAN,USB power...what's left? audio ,mmc reader...what am i missing?

[mcplslg123]

Re: Lenovo ideapad 510 15ISK- power problem

@huzo, did you followed post#3. If you disable onboard ram, mb will not try to post-so there will be no reboot. I beleive,you are thinking in the wrong direction.

[huzo]

Re: Lenovo ideapad 510 15ISK- power problem

It wasn't water damaged,there is no corosion, i flashed the right bios, it came to me with that problem even before flashing the bios, after flashing it acts the same.... i know that it wouldn't POST without ram, i was just making sure that it does the same as without bios chip...

something resets the board right after it should start , and that's the problem...