GTX 1080 strix no output / 5V rail missing

Danteashen

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Hi everybody i'm new here and i'm trying to learn soldering !
I ve got a gtx 1080 strix with no display, show in device manager but crash when driver installed (nvlddmkm.sys BSOD)
I ve flash vbios many times with no error (100% please reboot to take effect)
When i ve opened the card, and tested rails, 12v ok/ 3.3 v ok / 1.8 v ok / 5v missing or low
i have no voltage on vram or the two Vrm for memory. but all others vrm are at 0.8v and working well

i've tried to find a short on 5v rail but i struggle to find the short
so my question is do you have any idea or guide for me ?

thanks everybody ! i gonna make some pictures tomorrow with measures i ve took
 

Danteashen

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hi thanks for your answer i've tried to measure voltage in (voltage mode obviously) at the red spots here, i've tried to find a short at these point with resistance mode and diode mode too but nothing.
 

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bigdogchris

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Check out NorthridgeFix on YouTube. He has put up a lot of videos of fixing 10 series power issues.

One of his more recent video showed an obscure R987 resistor on the back of the board that prevents 5v. There are many other videos as well.
 

Danteashen

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hello there thanks ! i'm watching many of his videos cuz that guy is a beast ! it helped me many times but for that card i'm stuck !
 

Danteashen

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i can't remember exactly by head but i'll check tomorrow, but i'm pretty sure it was normal value
 

Danteashen

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so this is all measures i have so far i think it's possible memory mosfets on the top right are dead ? oh and the little blank square is 1.1 V
 

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RazorWind

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so this is all measures i have so far i think it's possible memory mosfets on the top right are dead ? oh and the little blank square is 1.1 V
What resistance, in ohms, do you have from the memory inductor terminals to ground?
 

Danteashen

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i've tested mosfets and they re goods no short nothing, what do you call a memory inductor terminal ? can you show me where it is ?
 

RazorWind

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i ve measured 0.9 ohms to ground for the two grey inductors on top is it that ?
Yes. In the picture you posted, the two large inductors at the top of the row are for the memory power rail. 0.9ohms is probably a short. You should have at least 30 or so, as I recall.

So, your next step is to hunt for a short on that rail.
 

Danteashen

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yeay but the problem is i have 0.9 on all the row of inductor all grey ones (10 of them) so i don't understand
 

Danteashen

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between all of them i have 1.1 ohm. on all the vrm and vrams area i have between0.9 and 1.45 ohms everywhere
 

RazorWind

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Ok, so if you have less than one ohm of resistance between the memory power and GPU power, that means you have some sort of catastrophic failure somewhere. This can occur in a few places, but the most likely is the GPU die. The second most likely possibility the PCB itself. A remote possibility is the GPU/Memory power controller, which is usually shared.

You can try voltage injection to see if you can determine which one it is, but most likely, you'd need to replace the GPU to get this board working again.
 

Danteashen

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wow thanks the fact is, the board is powering on with fan spining and lights on ! i've got voltage at some points like 12v and others but that's just that area which i don't know don't get power ... can you tell me where the gpu memory controller is ? oh and when the card is on, the gpu die starting to heat slowly like normal
 

RazorWind

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wow thanks the fact is, the board is powering on with fan spining and lights on ! i've got voltage at some points like 12v and others but that's just that area which i don't know don't get power ... can you tell me where the gpu memory controller is ? oh and when the card is on, the gpu die starting to heat slowly like normal
At the risk of sounding like a jerk, if you need me to tell you which chip is the controller, you really have no business trying to repair a graphics card. If you intend to enjoy success in the future, this is something you need to be able to figure out on your own.

Here's a hint: Read the markings on each of the larger ICs on the board, and use those to look up data sheets. The memory controller will be the one that the datasheet calls a "power module controller" or "buck converter controller."

The GPU getting warm just means that current is flowing through it - it doesn't necessarily imply that the GPU is functional, and given that our short is most likely on the GPU, it's even a potential indication that the GPU is dead. You can check this putting some isopropanol on the GPU die while it's powered on. My guess is that you'll have one spot that gets really hot.
 

Danteashen

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no problem in the first post i've said i'm new in that kind of thing, i'm trying to learn, i'm trying to read datasheets to know which value i need to check, making my own process here. maybe it's just the gpu but i want to be sure that it's not something else. and i found the controller in the top right of memory vrms and is okay but i think the black power caps on the back are dead i need to find 470 uF but nothing
 

RazorWind

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Your problem is definitely not those capacitors. Remember, you have a short from one power rail to another. The capacitors should never be connected to more than one rail.

The controller is most likely the square component to the right of the core phases - the one not labeled "ITE." The one labeled ITE is probably related to the RGB disco lights. The small IC near the top is probably a phase doubler or VRM phase controller.
 

Danteashen

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yeah i see the ITE i've checked these ones and nothing bad i think no short in diode mode and resistance seems good
 

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Danteashen

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i ve found the buck controler in bottom (pgu1) and seems good voltage pass through it how do i know he s bad ? well i'm not sure but resistance to ground goes up and down really fast like 20ohms to 400 then go back to 55 ohms then 350 in a couple of second
 
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