Acer AN515-55-528T FH52M LA-J891P - Short ciruit after PQW1 MOSFET on +1.35VSDGPU rail.

[joshAU]

Hi all.
This notebook was showing no signs of life.

I removed the FH52M LA-J891P mainboard and found that there was 19V at the DC jack.
However there was zero volts on the two PRB2 and PRB46 resistors immediately after the two polarity protection MOSFETs (PQB11 & PQB12).

If I remove the PQW1 MOSFET, the 19V rail starts working, and I can turn on the unit - at least I get the fans, and the power light comes on, when I simulate the power button being pressed. No display.

I tried replacing the MOSFET with a new one, but again no voltage on the resistors above.
With PQW1 removed, pads 5,6&7 show a short to ground (zero ohms).

I assume that either the GPU, a memory chip, or one of the capacitors on the rear side of the PCB near the memory chips, and the GPU, is shorted.
They are all on the +1.35VSDGPU rail.

I am wary to inject more than 1 volt into this rail, so I am having difficulty isolating the cause of the short to ground.
If I inject exactly 1V after the MOSFET, it draws approximately 1.3A, yet nothing gets warm anywhere on that rail, which makes me think it may be the GPU.

The schematics and boardview were from here (thanks to aico60):
https://www.badcaps.net/forum/troubl...atic-boardview

I've tried removing a few large capacitors, (PCW9, PCW10 & PCW52), and visually inspected all the smaller 0402 & 0201 capacitors.

Any suggestions of what to try?
Is the GPU dead?
If so, can it be disabled and instead just use the integrated GPU in the i7-12650H CPU?

I had a search of the forums, and was able to get the schematics and boardview files, thank you, but apart from one post, I was not able to find out much more information.


Thanks for any help you can provide.

[piernov]

Shorted MOSFET on VRAM power rail very often means all VRAM ICs + GPU are dead.

[joshAU]

Shorted MOSFET on VRAM power rail very often means all VRAM ICs + GPU are dead.

Thanks piernov, I appreciate your advice.

I was hoping it was not the GPU, but was suspecting that it might be.
Thank you.

[joshAU]

I removed the Mosfet PQW1 and tested booting using the CPU's GPU.
Unit powers on and boots using Intel GPU integrated in the CPU.
Tests fine, and customer is happy.
Thanks again.