Asus GU502GU no powering up

[Garibean]

Hi !

I'm becoming crazy for this one, i have a non working asus GU532GV-ES023T.

I checked for short on the main power rail and couldnt find anything.
Then i checked +nvvdd for the gpu and found a short (0,1 ohm maybe a little more), but i learned later that it's normal for a gpu to have a resistance this low.
I checked the cpu and got 2 ohm, it's also normal here.
I noticed that someone have already worked on it and found a short between 3vadsw_LG_30 and gnd.
The last person made a short between this line and gnd on a mosfet. I resolved the short with my iron and thinking that it would do it, i plugged the pc on.
Nothing, i checked with my thermal camera and saw that a small ic is getting hot : PU8701 aka sn51285arukr.

I am kind of stuck here because i don't know if replacing it will resolve my problem... can i remove it and check for short then ?

[mon2]

Re: Asus GU502GU no powering up

If this component is getting hot, remove all power -> measure the resistance to ground on the output of this IC. What is the resistance reading ?

https://cdn.badcaps-static.com/pdfs/...8733694997.pdf

[Garibean]

Re: Asus GU502GU no powering up

So i found 7 ohm on the pin 12 (Vin) +5VAO, so it does mean that i need to check here ? Do i need to do voltage injection on this pin ?

also here are the schematics

Schematic and boardview ---> https://www.badcaps.net/forum/showth...67#post1142867

[Sephir0th]

Re: Asus GU502GU no powering up

VIN is +AC_BAT_SYS, so the Main Power rail. It is impossible to have the Main Power rail present with a 7 Ohms to GND there.

[Vesko356]

Re: Asus GU502GU no powering up

So i found 7 ohm on the pin 12 (Vin) +5VAO, so it does mean that i need to check here ? Do i need to do voltage injection on this pin ?

also here are the schematics

Do NOT attach schematics here!
Reminder: rules and organization of this section
https://www.badcaps.net/forum/showthread.php?t=117483

.

[Garibean]

Re: Asus GU502GU no powering up

Do NOT attach schematics here!
Reminder: rules and organization of this section
https://www.badcaps.net/forum/showthread.php?t=117483

.

I'm really sorry for that, i will not do it again. Thank you for the link !

VIN is +AC_BAT_SYS, so the Main Power rail. It is impossible to have the Main Power rail present with a 7 Ohms to GND there.

I found a ic that was hot with voltage injection, i removed it, now i have 60 ohm to GND on this main power rail, could it be this one ?
I tried to look, on the ic that i removed, for any short circuit and found 1.5 ohm to the GND of the IC, is it normal ?
For precision, it was this one APL5930QBI-TRG aka PU8602 ont the schematics

[myth77]

Re: Asus GU502GU no powering up

On main power rail resistance have to be in kilohms. How much voltage did you inject and how much current it is drawing?

[Garibean]

Re: Asus GU502GU no powering up

I injected 1volt 3 amps but it was taking 0.7amps

I check and i have 60 ohm the +3v line too

[Garibean]

Re: Asus GU502GU no powering up

Do you have any ideas ?

[Sephir0th]

Re: Asus GU502GU no powering up

60 Ohms at +3VALW/+3VS is usually a bad sign. Since with 1V likely nothing will significantly heat up from a 60 Ohms short (except thermal camera available), feel free to inject 3V 3 Amps and see what is getting hot, especially the PCH.

[Garibean]

Re: Asus GU502GU no powering up

So little update ! I continued searching and found 0 ohm on the +1.05vsus ! On the schematics, it looks like it's linked to the pch so i tried voltage injection and the pch was hot...
It's the hm370 sr40b, i will try to change it and hope that it works.
Do you think that it's the pch ?

[mon2]

Re: Asus GU502GU no powering up

Yup. Game over.

[Garibean]

Re: Asus GU502GU no powering up

The good news is that i found why there was 60ohms on ac_bat_sys, a mosfet was shorted, now i have kohms on the main power rail !
Do you think that it's worth it to change the pch ? I'm planning to buy a pre heater to change bga chips

I have also an other question about the +NVVDD being 0.1ohm, i am not making any mistakes here, this is normal to have 0.1ohm ?

[Sephir0th]

Re: Asus GU502GU no powering up

If you have to ask, don't try it...

[Garibean]

Re: Asus GU502GU no powering up

If you have to ask, don't try it...

I am learning sorry ^^
I read a lot that it's 50/50 when replacing a pch, i even saw a youtuber called Sorin that changed a sr40b with only a hot air station.

[mcplslg123]

Re: Asus GU502GU no powering up

Never try those gimmicks of replacing a PCh with hot air gun. Only a BGA machine can do this job perfectly. The shorted mosfet was a high side fet on VCORE circuit?

[Garibean]

Re: Asus GU502GU no powering up

PQH8702 was shorted, this mosfet was taking care of 3vadsw, next to it was pql8703 which was shorted because the last person didn't do a good soldering job and shorted the 3vadsw of the mosfet to gnd (that explain maybe the death of pqh8702 which was in front of pql8703)

[Garibean]

Hi, little update, the pch was shorted. I asked a friend of mine who works in an electronic school to change it with the bga repair station. He successfully changed it but detected 1 short in the X-Ray machine. I told him to give up because that was a pain since the beginning.
Thank you every one for your help !