2080 ti GPU Repair question

[Eg3300401]

I recently bought a 2080 ti for cheap. I am trying to repair it. It has what i believe to be the PEX rail shorted out. I tested for the main rails, and all rails are there and non are shorted out. When i pulled up a reference schematic, i measured everything on the PEX rail and every cap is shorted to ground. does anyone have any idea what could be shorted besides the GPU chip?

[MathWizard]

So do you mean you removed all the caps, and the inductor, and the short is still there ?

 I found a shorted little SMD cap on one of my GPU's memory rails. I actually cracked it by accident, just by dropping a screwdriver on it. To find the short, I ran some low voltage at a high enough current into the rail, that I could feel the cap heating up to the touch.

Just reading this to remind which rail is PEX, it doesn't sound good.
https://repair.wiki/w/PEX_Rail_on_Pascal_GPUs

[Psi]

You can also put a little some isopropyl alcohol on the pcb and watch where it evaporates from.
The area/part that is shorted will get hot and the isopropyl alcohol will evaporate from there first and quickly.

When injecting voltages on a GPU you want to use a very low voltage, 1.0 volt or less. That should be safe for any rail of the GPU.
Even when you are injecting onto a 3.3V or 12V rail for example you should use 1V because the GPU Vcore runs at 1V and that voltage might be produced from the 3.3V rail for example and there might be short between the rails.

You must limit the amps and start low (maybe start at 200mA).   You want the short to get hot enough to find with the isopropyl alcohol but not so hot it damages anything. So start low and use the lowest amount of amps you need to see where the fault is.

[Eg3300401]

Thank you, I will try it.

[Eg3300401]

I removed the top caps, a few resistors and the the inductor but the short is still there. I even replaced the inductor because it's bad but every cap is shorted.

[kripton2035]

you can also build yourself a "shorty-with-display"
invaluable tool to find these kind of shorts quickly...
http://kripton2035.free.fr/Projects/shorty-display.html
https://youtu.be/L4V3BWReZLY

[MathWizard]

Now I'm forgetting, the core and rail's on these read as almost a dead short anyways, especially on cheap DMM's.

The last GPU I worked on, the memory and core had resistances around 0.3 and 0.6 ohms, I'd have to look it up. But if you ask anyone over on Badcaps, they'd know for sure.

Have a look around on Badcaps.net, there's quite a few schematics over there, for 1080 ti's anyways.

[Psi]

You may have to unsolder the core reg inductors, or find another way to isolate the GPU core.

[wraper]

Now I'm forgetting, the core and rail's on these read as almost a dead short anyways, especially on cheap DMM's.

The last GPU I worked on, the memory and core had resistances around 0.3 and 0.6 ohms, I'd have to look it up. But if you ask anyone over on Badcaps, they'd know for sure.

Have a look around on Badcaps.net, there's quite a few schematics over there, for 1080 ti's anyways.

Only Vcore is fraction of an Ohm, normal memory resistance in tens to over hundred of ohms depending on type. I don't recall exact resistance 2080ti PEX, but it certainly must not be a dead short like Vcore, there should be at least a few ohms for sure. 1080 for example has a few tens of ohms and 3090 over 5 ohms. If it's dead short it does not necessarily mean it's a dead GPU, it may be a shorted VRM or some ceramic cap too. Remove inductor to see if short goes away, if it does not you may try injecting low voltage into the rail and look with thermal camera.

[TomKatt]

This kind of repair is well beyond me, but I still enjoy watching videos of people working on them.

It seems that often an overcurrent can cause traces inside the pcb to short - I've seen people dig a 'hole' in the pcb with a dremel to get to the affected area and then run some jumper wires to repair the destroyed traces.

Would that be a possibility in your case?

Of course, you need to locate the area first.  A thermal camera seems like the best starting point here.

[wraper]

PCB usually burns under VRM when some power stage explodes and it's quite obvious. In other places it's quite rare.

I've seen people dig a 'hole' in the pcb with a dremel to get to the affected area and then run some jumper wires to repair the destroyed traces.

It's done for entertaining content. IRL it does not make much sense unless it's not severe. Makes more sense to use it as component donor.

[MathWizard]

Yeah some rails are 20, 100, 600ohms. But the main ones, are often under 1 ohm.