We’ve taken a look at two successful repair attempts recently, a dead RTX 5090 and a dead RX 7800 XT being revived from the silicon grave. However, it’s equally important to see the other side of the coin — what happens when the repair doesn’t go right? What if the card is fated beyond a fix? That’s what occurred with Northwest Repair’s latest job, where a specially endowed RTX 4090 turned out to be more deeply dead-and-buried than initially imagined.
A heavily modified RTX 4090 with a rare 48GB memory PCB showed up on Tony’s bench, courtesy of a customer who’d already tried fixing it themselves with a brutal 21-volt, 21-amp voltage injection. Spoiler alert: it didn’t end well. This wasn’t a standard card either, this custom PCB had double the memory of a standard RTX 4090 but came with all the risks of poor cooling and cheap power components. Tony later called 48GB cards unreliable, due to the events that unfold.
Taking it apart, the first thing that jumped out was the terrible cooling on the back memory chips — held in place by a flimsy bracket that did little to keep temperatures in check. The fan cables were pinched, which screamed careless handling or some rushed, rough repair attempts before. Testing with a multimeter revealed a dead short on the 12-volt power rail and the 1.8 and 1.2-volt memory rails. Basically, this board was cooked (literally).
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Thermal imaging and a cautious, low-voltage injection painted a clearer picture, since one memory chip literally glowed under power—a dead giveaway it was fried. The GPU core itself showed hot spots, meaning internal shorts were present there too. Some more probing by the technician revealed the real culprit, which was a failed driver MOSFET in the buck converter. Instead of stepping down 12 volts to the lower memory voltages, it had shorted and shoved the full 12 volts directly into the memory, roasting multiple chips and damaging the core.