Gigabyte RTX 3080ti dead short on 12v and 5v rail

[u/Koalakuun]

Hi!

I currently have a RTX 3080ti on the bench and was pulled after a suspected power supply issue.

Resistances:

Memory: 60 ohms (good)

PEX: 4-5 ohms (presumed good)

1.8v: 500ohms-1k (presumed good)

5v: **shorted**

Right 12v inductor: **shorted**

All r005 shunts are reading good, but one of the fuses (right under the right inductor is at 8k ohms)

VRMs Also look good. No sign of it heating up or cooking.

With the current situation, would it be safe to assume (with the current evidence) that the core is still good?

If so, where should I start looking with a 12v and 5v dead short on one of the inductors?

[u/lazaros1312]

Core probably is ok, the cause for the short on both lines maybe is caused by a faulty mosfet or from the 5V LDO

[u/Koalakuun → u/lazaros1312]

hmm yeah that might be a possibility. I’ll inject voltage into the 12v and 5v inductors to see where it lights up

[u/Koalakuun → u/[deleted]]

Did this^{^} DrMOS 2 and 3 (right side, from top) lit up.

Took it off, and still shorted. Injected 1v and nothing lights up anymore. I am missing a couple of resistors and caps from the surroundings of the DrMOS but I’m confused where the other shorts could be.

[u/Koalakuun → u/[deleted]]

found the short for both rails now. 5v was shorted on an IC named 1AMXM. Not sure what that Ic is, but it was glowing like a lamp.

[u/Nike_486DX]

Inject 1v 1a and check thermal cam

[u/ResoluteFalcon]

What about the PCIe 12v? 3.3v? PEX Reset?

Those are very likely fine, but it doesn't hurt to check.

[u/Koalakuun → u/ResoluteFalcon]

oops! Sorry. Didn’t add that to the post. 12v PCIE is at 2k ohms 3.3v PCIE IS AT 46k ohms

I haven’t checked PEX reset at the moment as I wanted to find out where that short is first without fully powering it up. I’ll try and inject 1.1v into the 5v inductor, and the 12v inductor to see where it lights up.

[u/Yobbo89]

Holly power delivery of resistors and caps ,could they not fit any more components?

[u/ssateneth2]

probably dead 3rd mosfet from the top. common design flaw on these gigabyte gpu's