Broken Aorus GTX 1080ti. Seeking help diagnose problem and to replace broken module.

waylmaster

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Hello I am not new to system components but I am new to GPU repair and PCB circuitry. I recently purchased a broken Aorus 1080ti locally for 60 dollars with the intent to fix. I have diagnosed the problem to be a blown module located in the vcore. I dont know exactly if it is a mosfet but I do know that it is manufactured by Alpha & Omega semiconductors (AOZ5036) http://www.aosmd.com/res/data_sheets/AOZ5036QI-01.pdf.

I have already purchased some replacements from Aliexpress (https://www.aliexpress.com/item/4000786926977.html?spm=a2g0s.9042311.0.0.38ef4c4dIoAR5x).

I still don't know if the short was caused from internal problems or if it was purely a PSU issue. I need some help on identifying the cause, and also need help on what I need to replace the module. I have included multiple images of the damage and surrounding area of the pcb.
 

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Yeah that part is a mosfet. The issue is just replacing the part usually doesnt fix anything, as what caused it to blow is likely still an issue. Plus it may have done other damage to the card when it blew.
 
RazorWind

I have read many of his fix a video card threads. Very knowledgeable and informative with things like this.
Hopefully he can pop in here and help you out.
 
The component circled in red is not actually a MOSFET, but rather a device called a "power stage module," which contains two MOSFETs and the phase control IC all in one little package. The PCB manufacturers like them because they tend to be quite powerful, but they're also pretty compact, which makes the board easier to lay out with a bazillion phases like this one has.

What you have here is very clearly a high-side MOSFET failure. If you look at the diagram in the datasheet that shows how it's laid out internally, you can even see that it's the high side FET (the one that handles 12V) that failed and blew a chunk out of the casing. You got pretty lucky that it's this obvious - you usually have to either do voltage injection, or just start removing them until you find which one it is. A high-side failure happens primarily due to heat, either just thanks to poor cooling, or because the gate voltage is too low. Excessive heat over a long period of time seems to be the most common reason this happens on graphics cards, but you shouldn't rule out the possibility that this was caused by low gate voltage. A low gate voltage situation typically occurs for one of two reasons:

1. A failure of the bootstrap capacitor
2. A weak power supply, on designs that drive the gates directly with 12V, or a weak VRM elsewhere on the card in designs that power the gates that way. These power stages use 5V on their gates, so they're the latter type.

I'd probably try just replacing the power stage, though, versus trying to troubleshoot

As for repairing this... Man, this is going to be tough if you've never done SMD work before.

You will need, at least:
1. A hot air station
2. A soldering iron
3. A high quality flux
4. Tweezers
5. Really good vision or a microscope
6. Leaded solder
7. PCB preheater
8. Replacement parts

The trouble is, as I mentioned before, these power stages are very sensitive to heat, but they're also quite large, and they're located in a part of the board that is specifically designed to act as a heatsink. This means that while you can physically remove the dead one by just heating the crap out of that part of the board with your hot air station for several minutes, you will likely have to run your hot air station so hot that you will damage the ones next to the dead one in the process, and you will also likely damage your new power stage when you attempt to install it, if you can even get it to solder right. I'm batting about .050 soldering power stages with hot air alone. It works once in a while, but it's clearly not the best idea.

The key here is that you need to heat the entire board to about 150C from the back using a PCB preheater, and then use the hot air station to finish melting the solder, clean up the pads with the soldering iron (getting just the right amount of new solder on them, which is kinda tricky), and then apply more flux and install the new power stage with the hot air wand. You have to do all this pretty quickly, since the power stages are designed to be kept at solder-melting temperature for about two minutes over their entire life cycle, and they've obviously already been soldered on there once.
 
Awesome write up man.

I've tried replacing chips on phones, not easy at all. This looks like a nightmare.
 
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