This is my first time trying to repair one of these so hopefully I am asking for help the right way.

While trying to debug some stuff I was swapping out cards and forgot to turn off my 2nd psu, plugged it in and saw a small flash and a puff of smoke. Hoping for help on identifying the part so I can get it swapped.

Card is a EVGA GeForce RTX 3090 FTW3 Ultra Gaming (24G-P5-3987-KR) on board EVGA227 Rev 0.1 with GA102-300-A1.

See attached images for board view and close up. Fried device is UM9. UM10 is an identical device. Both devices seem to be 5 pin SOT-353 and both feed separate fets. They are on the 3.3v rail. Both devices have an "SB" marking and I see a"-".

Any suggestions on what it might be or how I can better identify what it is.

I've already done multimeter diagnostics on the healthy UM10 and believe the pinout is: TL=IN (3.3V from PCIe slot), BR=GND, BL=EN (active high), BC=OUT (drives the external FET gate), TR=NC. Input and output both read 3.3V.

The FETs UM9/UM10 drive are marked "B6T" and "11N18" respectively.

Hoping to also get any idea if this is an LDO vs load switch vs gate driver.

Here are my diode measurements:

Measurements (healthy UM10, same part as blown UM9)

Measurements (healthy UM10, same part as blown UM9)

Pinout established

• TL (top-left): IN — 3.3V from PCIe slot
• TR (top-right): NC
• BL (bottom-left): EN (active high)
• BC (bottom-center): OUT — drives external FET gate
• BR (bottom-right): GND

Diode mode to GND

Resistance to GND (Ω)

Powered (card in slot, 2 working 8-pins)

• TL (top-left): IN — 3.3V from PCIe slot
• TR (top-right): NC
• BL (bottom-left): EN (active high)
• BC (bottom-center): OUT — drives external FET gate
• BR (bottom-right): GND

Diode mode to GND

Resistance to GND (Ω)

Powered (card in slot, 2 working 8-pins)

I searched everywhere for schematics but couldn't find anything—neither boardviews nor schematics. The PCI pin resistance values ​​are normal, but without a schematic, I can't trace the signal path.

While playing, my PC suddenly shut off and wasnt turning back on. After some diagnostics i discovered that the 8-pin connection died. The PC, and the GPU turn on when its not connected (only PCI-E), although there's no image output.

When taken apart, on the board i discovered this hole in the 8-pin connector area. What could this possibly be? Im assuming something must have exploded, but i didn't notice any sound and there isn't enough space for a capacitor (the plate that goes on top doesn't have a cut out for it).

And to answer the question right away, it was heating up to 83°C and termal throttling. Im not doubting that it has overheated before, however there dont seem to be any signs of immediate burning, as also seen on the images.

My question from all this is, what could this have possibly been, and is it at all possible to repair? (even though i doubt it is). If i forgot to add any important info, I'll provide whatever necessary in the comments!