As soon as i plug the charger the CPU get extremely hot

[mnciks11]

Hello guys, I'm diagnosing the Asus PU551LA Rev 2.0, I don't have the schematic. The laptop is dead, not charging, not turning On, as soon as i plug the charger the Cpu get extremely hot, there is a shorted to ground cap near the cpu, and another shorted to ground output coil but I'm not sure if it for the cpu or not.

Please see attached photos and help guys

[KvnTM]

Re: As soon as i plug the charger the CPU get extremely hot

3.3v on PCH present? Take the heatsink off and feel if the smaller die gets hot very fast.
If so then you have a dead PCH.

If the cap is shorted then the coil would also be shorted to gnd if they are on the same rail. Should make sense.
Replace the cap and short should be gone.

[mnciks11]

Re: As soon as i plug the charger the CPU get extremely hot

3.3v on PCH present? Take the heatsink off and feel if the smaller die gets hot very fast.
If so then you have a dead PCH.

If the cap is shorted then the coil would also be shorted to gnd if they are on the same rail. Should make sense.
Replace the cap and short should be gone.

I don't have any 3.3v, bios chip doesn't have 3.3v, there is no short on the 3.3v rail. Why the CPU is getting hot as soon as charger plugged in, shouldn't it start getting hot as soon as all the power supplies are working?, brother I'm confused here, the laptop is missing 3.3v and the processor is getting hot

[mnciks11]

Re: As soon as i plug the charger the CPU get extremely hot

How do I check 3.3v on the PCH if the 3.3v is missing?

[piernov]

Re: As soon as i plug the charger the CPU get extremely hot

As KvnTM said, " Take the heatsink off and feel if the smaller die gets hot very fast."

[KvnTM]

Re: As soon as i plug the charger the CPU get extremely hot

I don’t have any 3.3v, bios chip doesn’t have 3.3v, there is no short on the 3.3v rail. Why the CPU is getting hot as soon as charger plugged in, shouldn’t it start getting hot as soon as all the power supplies are working?, brother I’m confused here, the laptop is missing 3.3v and the processor is getting hot

3.3v and vcore are the two primary high current power rails to the SoC.
VCore is most likely not present since it is not turning on.
Other Auxiliary power sources can't deliver enough current to heat it up so badly.

I sadly can't get a schematic or boardview for this model without paying some shady Russian website.

Just take the heatsink off and do what I said. Easiest method to tell if you can scrap the board.

[mnciks11]

Re: As soon as i plug the charger the CPU get extremely hot

as kvntm said, " take the heatsink off and feel if the smaller die gets hot very fast."

yes i did, as soon as i plug the charger, the cpu get extremely hot

[mcplslg123]

Re: As soon as i plug the charger the CPU get extremely hot

yes i did, as soon as i plug the charger, the cpu get extremely hot

The soc here has two components-pch+processor-though its soldered as single die. The smaller one is pch and the bigger one is processor as@piernov and Kvntm has explained. You should give a definite answer which die is heating up.

[KvnTM]

Re: As soon as i plug the charger the CPU get extremely hot

I made an image as explanation for you.



Yours may look a little different but there should be 2 chips on the processor package. One is the CPU (Larger, mostly a wider rectangle) and one the PCH (Smaller). Take the heatsink off and put your finger on the PCH while no power is applied.
Now plug in your charger while still having the finger on it. If this chip heats up immediately you most likely have a bad PCH.

If you don't know what a PCH is:
PCH stands for Plattform Controller Hub and replaces the Northbridge and Southbridge into a single chip directly on the processor.
Back then North- & Southbridge were two separate chips on the Mainboard. The Northbridge was handling PCI(e) and RAM. The Southbridge was the controller for peripherals (USB, IDE, SATA, .....).

They combined those to minimize power draw and improve speed on ultra low voltage processors like the one on your board.

If the PCH is bad you would have to replace the whole processor or get a new board. Replacing the processor is not easy and can't be done without a BGA rework station. It does NOT work with an hot air gun!

[mnciks11]

Re: As soon as i plug the charger the CPU get extremely hot

I made an image as explanation for you.



Yours may look a little different but there should be 2 chips on the processor package. One is the CPU (Larger, mostly a wider rectangle) and one the PCH (Smaller). Take the heatsink off and put your finger on the PCH while no power is applied.
Now plug in your charger while still having the finger on it. If this chip heats up immediately you most likely have a bad PCH.

If you don't know what a PCH is:
PCH stands for Plattform Controller Hub and replaces the Northbridge and Southbridge into a single chip directly on the processor.
Back then North- & Southbridge were two separate chips on the Mainboard. The Northbridge was handling PCI(e) and RAM. The Southbridge was the controller for peripherals (USB, IDE, SATA, .....).

They combined those to minimize power draw and improve speed on ultra low voltage processors like the one on your board.

If the PCH is bad you would have to replace the whole processor or get a new board. Replacing the processor is not easy and can't be done without a BGA rework station. It does NOT work with an hot air gun!

Thank you so much fellows, thanks a million.


The PCH is getting hot

[KvnTM]

Re: As soon as i plug the charger the CPU get extremely hot

Thank you so much fellows, thanks a million.


The PCH is getting hot

Thats sad news.. You got 2 options now.
A: Scrap the board and get a new one
B: Replace the CPU

[hornylamb]

Re: As soon as i plug the charger the CPU get extremely hot

First.. Thanks a lot for explanation and what i was looking for.
Could you please let me know. recently i have found in YouTube comments , it say it is not safe to apply thermal paste on PCH. Is it that correct ?
because in some of YouTube videos i see somebody put thermal paste on PCH, i guess those people doing mistake.

[rediii]

Re: As soon as i plug the charger the CPU get extremely hot

thats not right. you should apply thermal grease on the pch as long as the heatsink is covering it... otherwise a thermal pad would be useful

[piernov]

Re: As soon as i plug the charger the CPU get extremely hot

For U CPUs (CPU and PCH on the same package), there shouldn't be thermal paste on the PCH die, except if there was some originally but that shouldn't be the case.