MSI GE66 Raider 10UH - Shorted High Side Mosfet

Hello,

This laptop had a short on the main power rail, which I was able to trace to a shorted high side of the dual N-channel mosfet, PQ23, highlighted in Yellow on the attached picture. I believe this is the VRAM power supply. I also removed the mosfet above, PQ26, just so I could test out of circuit. It is OK. With the mosfets removed, the main power rail is no longer shorted.
Checking further, all the GPU coils are reading 0Ω resistance to ground, so this probably means the GPU is dead. The two coils alongside the shorted mosfet, CHOKE11 and CHOKE13 read 20.6Ω to ground, which may also indicate VRAM damage.
There is an empty coil location on the board (Blue arrow). Would this be a suitable point to carry out a short circuit test?

Motherboard number is MS-15421 Rev 1.0

MendUsThis писал(а):I believe this is the VRAM power supply.

Hello!
Yes, exactly. I confirm.

MendUsThis писал(а):all the GPU coils are reading 0Ω resistance to ground

Are you sure there is a dead short to ground with 0.0Ω resistance?
For this type of the GPU chip I would expect a resistance of around 0.2 - 0.3Ω.

MendUsThis писал(а):The two coils alongside the shorted mosfet, CHOKE11 and CHOKE13 read 20.6Ω to ground, which may also indicate VRAM damage.

I would expect a resistance of around 30 - 40Ω on this two coils, so the 20Ω may still be acceptable.
In such a case the damage of the VRAM chips and the memory controller part of the GPU chip is unfortunately quite likely, but perhaps there is some small hope.

matic писал(а):Are you sure there is a dead short to ground with 0.0Ω resistance?
For this type of the GPU chip I would expect a resistance of around 0.2 - 0.3Ω.

Originally, yes I was reading 0.000Ω. I have now removed all 5 of the GPU coils and on the output pads of the coils I'm reading 0.3Ω. On the input pads, I'm reading 100's of kΩ, so maybe the GPU has survived.
Are there any other tests I could carry out or is it now a case of re-solder the coils, replace the mosfets and see if the laptop will power on?

I don't think there is anything you can do other then solder/replace the removed components and test the board.

After reassembling the laptop, it does now boot into Windows, but the RTX3080 GPU is dead

Works fine with the GPU disabled in device manager, but Windows locks up if I enable it.

Looks like I need to learn how to do BGA rework

Thanks for you help matic, it is much appreciated.