GPU surgeon attempts to rescue fatally-bent RTX 4090 that came in for a melted power connector fix — autopsy reveals shorted MOSFET that killed the GPU core

GPU surgeon attempts to rescue fatally-bent RTX 4090 that came in for a melted power connector fix — autopsy reveals shorted MOSFET that killed the GPU core

Dead RTX 5070 Ti with a literal burn hole gets resuscitated by an RX 580's VRMs in Frankenstein repair

“Screw this,” exclaimed the seasoned GPU tech, as he moved on to testing the GPU itself, pulling out the multimeter. There was a dead short on the 12V rail, 1.8V rail, and the memory, but the 5V and PEX were seemingly okay. After injecting current into the 12V rail, he formed the initial hypothesis. Under a thermal camera, he saw heat building up around the VRAM area, indicating that 12V was shorted to the memory and likely propagated further, frying other components. Checking the core’s resistance, however, confirmed that it wasn't shorted, so there was hope.

When put underneath a microscope, he discovered the card had previously been RMA’d, as it was in poor condition with a bunch of missing components, but nothing too egregious jumped out right away — except for grinding marks near a screw post, hinting that a Dremel was used there for some reason.

Next, a suspect VRAM module was removed, but the short still persisted, confirming the hypothesis that 12V reached the entire memory rail, likely taking out all the VRAM chips in the process. Tony grounded the memory rail to stabilize it before pushing a higher current to see what else was causing issues. Pushing 5 amps made the SIC653A power stage glow, indicating it failed and allowed the 12V to reach the memory. Removing the MOSFET made the short go away, and after replacing it with a new one from a donor board, he tested again.

The short on all the rails was gone, except for the memory. Tony once again injected a few amps into the VRAM, and sure enough, the core started getting hot, confirming a dreadful conclusion. He just performed an autopsy, not a repair, as the 12V had travelled through the memory chips and eventually reached the core, frying it in the process.

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